W210 CAN bus issues
 

Ok now it’s my turn for more fun. Sold the wagon to VStech and sure enough 2 of my 4 cars decided to protest. At the same time.

On Saturday, the E320 has lost its Y3/8n2 sensor on the conductor plate. It’s going to the dealer tomorrow, can’t DIY this one. $$$$.

You have to do a 722.9 transmission service on a lift since it’s a bottom filler. I have no easy access to a lift. And to make matters worse, they won’t sell you a conductor plate, because you have to code the new plate to the car, and it requires legit Xentry that can phone home. I knew this going in, I pulled diagnostics when I bought the car, and the error was in the history. I got the seller to drop the asking price about what it will cost for the dealer to fix. Just bad timing.

But on to the main part of the story:
On Sunday I did an oil filter and air filter change on the E300. 248k miles, been practically trouble free the 5 years I have owned it.
Got all done and went to crank it and it would crank but not start.
Acting like it had no fuel. It would spin for a few seconds and sound like it was going to catch and then the auto crank would stop the starter.
WTF.

Dug into it and determined that the fuel valve was not opening. No voltage at pin 4 of X22 (the fuel valve drive signal).

I thought, the only thing I unplugged was the MAF to make it easier to take off the air filter lid to change the filter. I checked and I had +12 and +5 V at the sensor, so that ruled out losing the sensor voltages from the ECU.

Tried to open the trunk and the PSE pump was cycling but the trunk would not open.

Got the computer hooked up and the CAN bus system is throwing faults left and right. On both the engine bus and the body bus.

I was able to clear the faults and everything scanned clear (except for one door control module that was reporting failed). I was then able to start the car like nothing happened.

Took the car for a shakeout run and sure enough about 5 miles from the house, it just flat died going down the road. I coasted into a parking lot and hooked the computer back up. Same thing, practically every CAN related fault showing on both buses. Cleared again and got it back to the house.

Had to run to Texas for a work trip Monday morning through today. So luckily older brother is out of town so younger brother could drive the ML320.

Obviously something failed non related to the oil change.

Maybe EIS failure, that is the device in common to the two systems.

Anyone out there got any ideas?

I’m going to try to get on it after dinner, first thing I am going to check is system voltage. I wonder if the alternator is going south.

Yikes...interested to see how this plays out.

This is the E300 right? How old is the K40 relay.

Not sure, I haven’t replaced it. I can look for date codes when I get out there to troubleshoot in a little while.

First, I'm not a Mercedes mechanic or a mechanic at all, really.

In my experience, when the can bus goes down, it's almost always one of a few things.

1) Broke/grounded wire. A broke or bad connection can be hard to diagnosis with a multimeter, you need to load the circuit. But if you're seen multiple faults, this is less likely.

2) A module on the can bus is bringing down the entire network. On a crank/no start where there's no CAN activity or faulty activity (i.e. low amplitude or the wave forms don't match) I've had a lot of success unplugging modules and seeing if the network comes back. I've seen many an ABS module take down a CAN network causing a no start. You pull the connector and brake fluid starts pouring out.

3) ECU. It happens.

Good to replace K40 "just because." Cheap and can cause all manner of electrical weirdness.

Well guess what. System voltage 12.1 V at idle (measured with my Fluke 87 at the jump start lug under the hood). Alternator time! I got 248k miles, not bad for the original alternator.

I suspect that the system voltage crashed while driving thus taking down the whole network.

With the car on a battery charger, all the engine CAN bus nodes (ABS, ETC, IFI, IC) report as healthy (ERE, Actual Values).

I do have an interior can bus issue that I have to run down but I don't think that's the issue with the engine control.

I found the screen in the HHT emulator (EZS, Actuations) that gives the run down on the whole body CAN network, and I have a CAN-H fault except when DCM3 (rear drivers door) module is unplugged from the harmonica.

12.1 isn't very low, cranking voltage will drop below that. I've had electrically noisy alternators cause odd problems on other cars, did you hang a scope on the alt output?

I did have an ignition module on a VW become overly sensitive to voltage causing a run problem. It would run fine with the alternator unplugged once battery voltage dropped a bit.

That 12.1 V was at idle and no appreciable load (climate fan off, lights off). I would expect at least 13.xx V.

I had the min/max function engaged so I could check the volt drop on crank but the lead fell off when the engine cranked so I didn’t get a good reading. I will try again later to pull this number.

I don’t have a scope but I did switch it to AC volts and had less than 100 mV so it’s not a blown diode.

What concerns me the most is we did not get a charge warning on the dash. They take the D+ to the dash but instead of the traditional bulb they have a resistor and a voltage input to the control logic.

I already have another alternator on order and it should be here tomorrow. I’m changing it on principle anyway (along with a new belt!) due to the age of the car and the fact that it will be at college with my son this fall.

Yes 12.1 is low for a running engine, but 12.1 should not prevent the car from continuing to run after initial start. Think about what happens when the alternator belt is removed to check for noises.

Perhaps the voltage regulator is working enough to energize the field enough to shut the light off but not enough for ample charging voltage.

That is what I’m thinking, regulator maybe going out. A new (rebuilt) alternator will be here Monday. I will be putting it in sometime next week when I get a work deadline out of the way.

Update:

Got the new alternator installed yesterday. System voltage 13.92 V at idle now.

If anyone following needs to do this, on a turbo engine, you will need to remove the charge air pipe from the turbo outlet to the intercooler rubber hose on the right side. One of the mounting bolts for this pipe is shared with the alternator bolt. It is an E-torx bolt and the mount point on the pipe is slotted. There are 2 more 10 mm bolts along the length of the pipe that have to come out and then it just drops out.

You can’t pull the alternator from the top, the water line connection to the radiator runs right over the top of the alternator.

Also you’ll need to remove the fan and shroud. It gets in the way just enough that it makes it impossible to extract the upper bolt for the alternator without it getting caught up in the fan.

And one more hint, you will need your lug wrench to release the belt tensioner. Well of course mine was locked in the trunk - if you disconnect the battery you cannot open the trunk on a W210. Luckily I had 3 other MBs around so we borrowed the wrench from one of the others.

Bolt torques: D+ lead 4 Nm, B+ lead 15 Nm, mount bolts 42 Nm. I think the bottom bolt was an E16 and the top an E14.

I also went to pull a part and found a left rear driver side window motor. I replaced this and now the system scans completely clean with no errors. The motor can be easily detached from the regulator - loosen two T25 screws and rotate the motor about 45 degrees and it pulls off the gear in the regulator frame.

I noticed the car that I had pulled the motor from that the regulator cable was a spaghetti pot in the bottom of the door. Not surprised. When I got the motor plugged into my car it would not run in one direction. On a hunch I put the car on diagnostics and found that the motor was inhibited due to being jammed previously. I was able to reset this and then the motor worked perfectly. I just had to retrain the up and down limits.

I will take the car out for a run today to make sure all is good but hopefully this is the end of this saga.

Yup... cars stick together


Ya get rid of their buddies and they protest.

Of course... they could be trying to get freedom as well...

Grass is always greener and all that.

Did you try to run the car after the alternator change?

Was the window motor motor only or does it have the CAN box built in?

What does this system use to determine window position? ( potentiometer , motor shaft encoder. )

If changing the motor was solution to the engine run problem, I wonder if a window position sensor failure to electrical ground could drag the CAN box down. ( RE: Voltage supply to position sensor is also used for CAN box functions. )

Another possibility is one leg of motor was shorted to ground and pulling power down. RE: The system is likely designed to run a H bridge with power to both sides of the motor when it is not moving. If one leg is pulled to ground, voltage to CAN box will fall.

Yes I have run the car after the alternator change. I am going to take it for a drive this afternoon before releasing it back to my son. I will have my computer with me just in case it locks up again.

On the rear windows, the CAN box is built into the motor. It uses two Hall sensors looking at the rotor to count revolutions and look for a stall (for pinch protection, or if the mechanism self destructs as is so common with these).

The way you train the system is by running the window up by pushing and holding at the momentary position until it senses the jam from hitting the top of the track. Then you run it down to the bottom in the same manner. It counts the revolutions between the two points so that is how it knows how to do auto open/close.

I took the old one apart for fun.

The H bridge is a typical arrangement on motor controls like this. MB has been using that arrangement since the direct wired window switch days. Of course now they use relays or MOSFETS instead of the switch points.

The motor has the following leads:
Power and ground (fed from a fused circuit)
CAN-H and CAN-L
3 wires to the local window switch (uses multiple resistors to determine position of the switch).
2 wires to the courtesy light (switched within the motor control box).

All the sensing and control is contained within the window motor assembly.

So the alternator change alone fixed the run problem? Or you only drove it after changing both the alternator and window motor?

I did the window motor first. I still had low voltage after changing out the window motor.

I took the car out for a drive last night and it did great. Voltage stayed up in the upper 13s the whole time.

Note that parameter 24 on the CCU reads low by about 0.7 V, they must have put the sensing past a diode. I confirmed this with my (recently calibrated) Fluke 87 that belongs to the company.

I would have a hard time believing that an internal fault in the window motor would pull the system voltage down to the low 12s without blowing a fuse. The alternator is 115 A and the battery has a 100 Ah capacity.

I noticed the CAN bus issue on the interior CAN after the first time I scanned the car when I got my Xentry last year. The fault was CAN-H shorted to + intermittently. Everything still worked so I kept putting off fixing it. When I decided to hand this car off to my son I wanted everything to work so I had it on the list of things to fix before he heads back to school. He’s a mechanical engineering major at Clemson so he has been a big help this summer. He did most of the work on changing the alternator and he is getting used to navigating WIS and Xentry.

After driving the car for over an hour last night with no issues I came back home and put the computer on it. No faults recorded and system voltage 13.91 V at idle.

Just 2 more system bugs to clear:
- the right side defrost vent does not shut all the way which fogs up the windshield down low on the right. That is an all day project since I have to take the dash apart. Although not nearly as far as when you pull the evaporator...
- the Hall sensor in the drivers seat head restraint adjuster has failed. Forgot to grab one from the 6 W210s that were in the Pull A Part this weekend. Might try taking the motor out and see if there’s a bad solder joint in the sensor first since it’s intermittent.

I was after what was causing the car to shut off. It is very important to understand why something failed and what fixed it.

Reading farther down, I see the CAN high was sometimes being pulled to +. This alone won't shut down the network because the CAN low is still working. Apparently when the car would not run, something was also stopping traffic on CAN low.

For others, CAN is a communication system that uses differential signals. When CAN High has a high voltage, CAN Low has a lower voltage. This increases immunity to noise and a failure of one leg won't crash the network.

Or the displayed CCU voltage is measured at long wire run that is loaded. ( Like with a fan. )

The window motor was not pulling charging system voltage down, it can't dissipate that much energy without a fuse clearing.

See my above, the CAN high fault was a warning sign.

Try explaining to a customer that nothing was done wrong in the recent oil change and a power window motor / controller can keep the car from running. . . "Oh, and you want me to pay for an alternator?"

More importantly, for the home repair guy, is to know where the CAN junctions are so nonessential functions can be removed from the network if it has crashed.

If the hall effect sensor failed open no big deal. However, if the sensor power has failed to ground, it could take out the seat controller / CAN network if it has one. Think about if the window controller was causing a CAN High fault and then the seat adjuster was causing a CAN Low fault causing the network to crash.

If the seat controller is on the CAN network, the car might stop again. " You changed my oil and did something to keep the car from running, sold me a window motor and alternator. It stopped again and now you want to sell me a head rest adjuster? " . . .

I think I finally got to the root cause.

I got it to stop dead again today and it has failed 100% this time. I replaced the transmission cooler flex hoses (one of them was weeping) and so I was idling to bring the car up to temperature to verify the transmission fluid level. And the engine just stopped dead without a warning.

Pulled codes and this time it was crank position sensor and the code will not clear. I checked the technical data in WIS, this is a simple inductive coil (passive sensor with no internal electronics). So I metered it and I have an open circuit at X22 (green connector in the module box) pins 12 to 13 looking toward the sensor.

I had gotten a stored crank position code last weekend when it died the first time. Shouldn’t have ignored that, it was trying to tell me something!

I am going to get into it later and verify it’s not a broken wire and then get a sensor on order. Hopefully this fixes the problem!

I have no regrets replacing the alternator, the one I pulled out looked to be the original. 20 years and 250 k miles, I could feel it was a little rough when I spun it.

Update: The wiring is good. I also tried cranking while viewing live data and the RPMs stayed on zero while cranking. I had all permissives true from the drive authorization and no CAN bus faults.

So I’m still not out of the woods yet.

New sensor came in and I got it replaced. Car started up no problem and I moved it out of the garage.

Couple hours later went to go put it back in the garage and it would not start again.

Got it to finally crank and run enough to pull it up in the garage.

Put it on the computer and it was showing P1335 (crank position) and P0300 (misfire).

Pulled up live data and the displayed RPMs were jumping around various values ranging between 580 and 760 between each scan (about 1 scan per second).

From my observation the engine is not changing RPMs that fast. And I think it would have a hard time actually doing this without violently shaking which it is not.

I proved this using a strobe tach app on my phone looking at the power steering pulley bolts (stand by the LF tire and look at the back side of the pulley closest to the pump). The bolts were holding rock steady when I strobed at the right rate (1518 Hz IIRC) to make them stand still.

I put my Fluke 87 on the signal lines from the sensor (connector X22, the green one in the electronics box, pins 12 and 13) and was reading about 3.8 V ac rms at idle. The frequency was jumping between 55 and 75 Hz. I did the math and realized that the pulse frequency of the sensor was equal to RPM/10. So the sensor is outputting a varying value.

I do not have a scope at hand to verify the waveform as shown in WIS.

I pulled the sensor out again this morning just to see if I had not seated it correctly. I even stuck my USB borescope cam down the hole to ensure there was nothing blocking the opening on the hole. It is possible to remove the sensor without pulling the manifold but you have to be a serious contortionist. 5 mm hex bit on a swivel and 2 x 12” extensions.

I pulled out the new sensor and compared the part numbers. The original sensor (date stamped 20th week of 1998 which correlates with a June production date for the car) has MB part number 003 153 74 28 and Bosch number 0 281 002 124.

The new sensor has no MB number (that area is blank) and Bosch number 0 281 002 123. The sensors look physically identical. The open circuit resistance of the sensor is approximately 1.3 kohms. Production date 5th week of 2018.

I went to http://aa.bosch.sk/download/sensory-2008.pdf and confirmed that the ...123 is the proper sensor model for this vehicle. Scroll all the way to page 224...

So now I’m stumped. Do I have a defective sensor? Unfortunately I cannot put the old one back in for comparison, it is totally open circuit.

I’m about to find a cheap oscilloscope on Amazon or eBay and figure out whether that waveform is correct.

There is also this MB link, scroll down to item 12...
http://manual.startekinfo.com/manual/JSP/de/3_3/m13.jsp

Note the item 5, the engine will just shut down if the CKP is implausible...

Scope on order from Amazon, stand by for update...

Finally got my scope in earlier this week and put it on the sensor. The waveform looks decent and stable and within the parameters as expressed in the WIS. Unfortunately the RPMs as reported by the HHT emulator are still all over the map.

I got with a local friend who has the same vehicle and put the scope on his sensor for comparison. Both waveforms appear identical.

Is the ECU itself faulty? I am at a loss for what to do next.

I really hate to dump this car, it is in great condition and was running great before all this happened.

Is it worth crying uncle and taking to dealer at this point?

Yeah I am about at that point. Going to speak with the service advisor at our local dealer on Monday.

The MB diesel computers seems to have something in common with VW diesels of the same era. ( EDC12 ??? ) Perhaps some VW guys have a similar problem and a fix.

Check the crank sensor wiring for a backed out contact.

Inspect pins on engine computer and plug.

Ohm out crank sensor wires from sensor to engine computer, you can do this the sensor plugged in. While doing this, wiggle the harness along it's full length.

Check wave form at engine computer connector, do this with the computer connected and not connected.

Remove the engine computer, open it up and follow the crank sensor pins to the board, look for a cracked solder joint.

Replace computer with known good part. The anti theft will be tied into the key chip , a reader box and the engine computer so all must match.

I had that thought as well on the harness.

Tomorrow I will try removing the engine harness and giving it a full inspection.

I tried opening up the computer but could not figure out how to remove the board from the casing without damaging something.

Last resort is a new ECU. I have been looking around at the options and it looks like rebuilt ECUs can be had from third parties. Some European sellers offer “unlocked” ECUs, I assume that if I have offline Xentry that I can initialize one of these.

If it comes to dumping this car, I won't mind a rust free southern 210. Hopefully it doesn't come to that, but keep me posted.

Well I had an interesting afternoon....

I got out there after church, 98 degrees today in SC, at least I’m in the garage with a couple big fans.

Got the intake manifold removed and the wiring harness removed. Really not all that difficult. It runs from the green X22 connector plus the one purple wire for starter from the control box, around the back of the engine block, picks up the starter, CKP, all 6 glow plugs, coolant temperature sensor, intake air temperature sensor, fuel valve, and oil level switch, and then another connector to the glow plug relay. Easy peasy to remove.

Discovered the fuel shutoff is weeping diesel out the connector port which explains the diesel smell I had been getting. Once I got under the manifold I could see the DVs are dry.

Got the harness spread out on the garage floor and inspected it. Wiring looked to be in pristine condition, my 1998 definitely has the improved wire that does not self destruct like the earlier models. Only thing that is an issue is the coolant temperature sensor plug cracked when I tried to unplug it. Looks like that is replaceable without having to replace the entire harness as there is a part number for the plug head.

On a whim I grabbed the old sensor and put my meter across it. Well what do you know it was reading 1.1 k ohms. I used a couple alligator clips and tied onto pins 12 and 13 on X22 with my meter and plugged the old sensor into the connector on the harness and it read properly. My son and I bent and shook that harness every which way and never got one bit of discontinuity.

So we put the harness back on the car and put the old sensor back in. I measured 1.1k at the connector harness X22:12 and 13, and then plugged it back in the computer box.

Got out my Star computer and hooked it up and started the engine. RPMs were reading 628 to 632, the car was running smooth as a Rolex watch. No codes other than P0100 mass airflow error since I was running with no intake manifold.

Shut down, quickly put the other sensor back in, started back up, could already tell it was running crappy again before I could even get to the RPM display in HHT Emulator. RPMs running between 550 and 750 again. It was throwing P0300 (misfire) and P1315 (CKP) codes again.

Shut down again, swapped in old sensor, started back up, back to normal running and 628-632 rpm. Ran the RPMs up and down with the actuation functions, the engine behaved perfectly and never threw any codes.

Buttoned up the harness properly and put the manifold back on, started back up, the car is running error free.

I got the sensor from Pelican, I will be contacting them in the morning to see about getting a replacement.

Also got to order a new fuel valve and noticed it’s time for injector line clips, several have broken, and need that sensor plug head.

When you looked at the wave form, was the voltage of all sensors tested the same? If the sensor isn't close enough to the ring, voltage will be low.

This is a sensor that slides into a hole in the block and has one retaining bolt correct?

Measure the distance from center of crank sensor to the mounting point on both sensors.

If the sensor is slightly too short due to a manufacturing issue, output voltage will be low / erratic. Check for casting flash on the sensor / something ( rust ) on the engine that would keep the sensor from fully seating.

While yours is probably non adjustable, some sensors ( Chrysler / Jeep ) have adjustable depth and use a thin sticker on the sensors tip to set depth. This spacer gets rubbed off at the first rotation. Granted the Chrysler unit is a hall effect and not an AC generating coil.

ABS sensors are generally an AC generating coil that can be affected by rust pulling the sensor slightly out if it's bore causing ABS to engage at low speed. Sensor depth is that critical.

The scope I picked up was one of the cheap Chinese ones that is the size of a deck of cards. It has a tiny LCD that is good for qualitative analysis and not so much quantitative. My friend came over and we were able to compare side by side but I did not pay attention closely enough to the voltage, I was more focused on the appearance of the waveform and the relative amplitudes. I think this scope can store data but I haven’t figured it out yet, I feel like Sandra Bullock in Gravity trying to figure out how to launch the Chinese escape pod.

Give me an old school Tek 24xx series scope like the old days. I almost bought one second hand but was afraid that it would get destroyed in shipment based on past eBay experiences. I was totally shocked when I opened the box with that Chinese scope, I was expecting something about the size of a small paperback book...

This is a sensor that goes into a bore hole and has a side flange for securing to the block. When I first ran into this issue a few weeks ago I checked the relative length of the sensors and cleanliness of the bore and all was good. I also looked to make sure the surface that seats on the block was clean. And that the sensor had no mold marks or anything else that would interfere.

This is a straight inductive sensor. It is not a Hall sensor; that started with the CDI engines, my OM642s all have Hall sensors. I think either we have a manufacturing defect (they are now made in Romania, so the production line has moved in the last 20 years) or else that difference in the last digit of the part number is significant.

Amplitude = voltage so if you were still on the same scale, the voltage comparison should be close enough. The scope might not have enough resolution to catch a drop out though.

You could rig up a toothed wheel and something to spin it for a test. For a 1 to 1 test, you would need a windowed wheel but a sprocket might be a more severe test. ( Bike sprocket , metal squirrel cage fan , knock out holes of a hole saw. )

Something haven't tried but that should work. Hold sensor close to a unshielded transformer. I'd keep a close eye on voltage using a meter, the turns ratio on the low side of a transformer to sensor might be high enough that voltage might go sky high. Typically, inductive sensors are in the 2.5 ish VDC range at idle.

If you have a high current AC load, holding the sensor close to a single wire might work. ( Not a pair as the magnetic fields will cancel each other out )

Gee, we have even outsourced NASA.


Yep, it is the type of sensor I was expecting, just like a gas M104 inline 6.



With the resistance being the same, I'd expect the parts to interchange. Did you hang a LCR meter on the sensors?

I found this part number standard a while back. It does give a window into how the MB system looks logical but isn't completely. Supposedly, one of the reasons MB bought Chrysler was to absorb the parts distribution system.

I just got Pelican to send me another sensor and RMA. If I had some free time I would rig up some experiments like that. Got to work for a living today...

I knew most of the background on the MB part system, it not only works with parts but you can also go into the WIS and look at the chapter number in WIS corresponding to the second group of digits, to find the instructions related to that system/part.

The part number that is different between the two sensors is the internal Bosch number that is off by one digit. The sensor I got from Pelican is identical in every way to the original MB sensor except the location on the mold where the MB part number would be is blank.

Replacement part on the way, we shall see if it behaves when it arrives.

Just so thankful it wasn’t the ECU that was the problem. I just got through the ($1850) transmission VGS replacement on my 2008 E320 Bluetec. That is dealer only since you have to SCN code it to the vehicle which requires verification back to the mother ship via online capable Xentry.

Well the replacement sensor arrived today. Popped it in (I’m getting real good at swapping these in and out quickly... but it sure is murder on your hands and forearms) but it too demonstrated the same behavior. Back to original sensor, engine runs perfectly.

RMA’d both sensors to Pelican and ordered up a genuine MB from the dealer, will be here Friday, stay tuned...

Is something like that literally dealer only? Do not some indies have the ability to contact the mother ship? Just curious....

They do offer the Xentry system to independent garages but it is extremely expensive.
Something on the order of $5-8k to buy the system and $20k/year to license it.

There are other options for fixing the VGS sensors. I did a bunch of research before settling on having the dealer do it.

First option is that several Chinese vendors on eBay are selling the sensors. It is not terribly difficult to change them yourself, if you are handy with a soldering iron. I was concerned that the sensors were probably second quality or counterfeit and I did not want to risk that on something so critical.

The other option is pulling your VGS and sending it off for repair. There are some companies stateside that charge in the $300-500 range for this work and a bunch in Europe charging a couple hundred Euros.

There are several pitfalls with DIY transmission work, the first is any contamination will lead to issues with the transmission. The other is that the VGS is an electrostatic sensitive device and you have to follow ESD protocols when handling it.

I have a local friend with a lift that I could have borrowed, but if the sensor replacement went wrong then the car would have been bricked and stuck on his lift. Can’t even get it out of park without the conductor plate installed and working.

After evaluating all this I just bit the bullet and had the dealer do it. No worries and if something goes wrong it’s on them.

Note that this applies to the 722.9 transmissions that were used starting in about 2006. The 722.6 as used on the W210 has a conductor plate but it is “dumb”, it just has the sensors and actuators. The transmission computer is in the control box under the hood. So there are no restrictions on changing the conductor plate and they will sell it over the counter to you.

The 722.9 transmission computer is on the conductor plate (what they call the VGS assembly). There are literally 4 wires to a 722.9: power, ground, CAN-H and CAN-L. It is also coded in the parts system as a TRP (Theft Relevant Part) and can only be released to the workshop from the dealer parts counter.

This is why I was pushing for detailed testing of the replacement and old sensor. Having one bad one is possible, two in a row isn't common.

How about a stack up of tolerances at the electrical connection? Perhaps the sensor has pins a bit short and harness connector pins too short or plastic interfering with full seating of the connector.

Doing the A B A testing shows there is a problem when replacement sensors are used but I like to drill down to the exact failure. . .and feed it back to the manufacturer ( not the seller as many times low cost parts are scraped by the seller and never are returned to the maker. ) . I've been through this a time or two or more.

Just think, somewhere out there another shop is experiencing a problem with parts / hidden problem and the customer is ready to sue, is posing all sorts of bad stuff to yelp and the net.

Thanks for the feedack.

I can certainly believe that 2 sensors in a row could have the same issue. I’m sure Pelican bought a small quantity of them from Bosch, probably ordered 8 or 10 or maybe 20 based on sales history. Bosch fulfilled the order, and I am quite sure they would have all come from the same manufacturing lot. When I called Pelican and had them send me another one, I’m sure the warehouse associate went to the same bin that he got my first one and grabbed another from that same group.

As for the connector mating issues, I investigated that while I had the harness out of the car last weekend (so that I could really see what was going on with the connector).

The sensor connector is coaxial. The contacts appear to be silver plated copper. The connection is protected from oxidation and moisture by an o-ring on the sensor body.

The contacts on the plug head also appear to be silver plated copper. The center contact on the sensor is made by a circular array of 6 or 8 spring contacts inside a shroud in the center of the plug head. The outer contact is made by spring contacts on the outer part of the plug head. There is also a barb molded into the outer plastic of the sensor, this is captured by a tension ring inside the connector shell.

While I had the sensor out of the car, I did check for floating contact by attaching my meter with alligator clips to X22:12 and X22:13 and setting it to ohms. I repeatedly plugged, unplugged, wiggled, shook, vibrated and did everything short of torture the sensor and plug combination. At no time did I lose continutity (approximately 1.1 k ohm) through the sensor.

I also checked the capture of the connector with the sensor. As soon as the plug head was placed on the sensor, even before the locking detent engaged, I had continuity.

So I think I’ve done my due diligence on the electrical connection.

All I can (and have done) is let Pelican know I have received 2 bad sensors in a row. I presume that Pelican has sufficient quality assurance protocols in place and will notify the vendor that they have received a customer complaint of a suspected defective part.

The sensors are in the hands of FedEx now on their way back to California.

I went down to the dealer and picked up my pile of parts.
Fuel valve, crankcase breather puck, injector line clips, new plug for the coolant sensor, and a new CKP sensor.

Opened up the sensor package and what do you know, it’s a Bosch 0 281 002 124 with a MB logo and part number 003 153 74 28. From the same plant in Romania.

Installed the other parts and the new sensor, and the car is running perfectly. Of course I had to purge the fuel system first so that was a little heart stopping, I forgot how hard it is to purge air out of an OM606. After nearly killing the battery it caught and fired on probably the last revolution it could muster. This set a ton of codes in the ABS, SRS, and other modules for excessive low voltage. Once I got all that cleared out the car is totally error free except for that stupid drivers seat Hall sensor on the body CAN bus. And the RPMs rock steady at 628-632.

First time this vehicle has left my house since June 17th. Took it out on the road and brought it back, still error free.

For future reference here is how to change a connector plug on the more modern engines.

First on the wire end of the plug head there is a little tiny release tab. You want to very gently pry on this while pushing the wires inward (push on the wires, don’t pull). This will remove the inner shell (with the wires and contacts still attached) from the outer shell.

Once you have the shells separated now you have to unlatch the wire retainer from the inner shell. This piece is gray and is in the shape of a C wrapped around the black body of the inner shell. You want to find the little groove in one end of the C and very gently pry up in that groove. This releases the gray clip from the inner shell. This reveals two little windows through which you can see the sides of the contacts.

Now go find yourself a paper clip and a small safety pin.

You want to insert the safety pin into the hole where the sensor pins would go if you were plugging it in. You want to take the end of the paper clip and push inward on the contact through the side window. You are compressing a tiny barb in the contact that normally locks it in place. At the same time you want to push in with the safety pin to withdraw the wire and contact from the inner shell.

Once you have both wires out then be sure to slide the old outer shell off the wire harness and then put the new outer shell over the wire harness. On the tail end of the inner shell you will see some tiny numbers, these are the contact numbers, so you get the wires in the right places. Now take the new inner shell and slide the contacts in. The barb has to face the side window. Be sure they click in. If they don’t click then draw them back out, and use the point of the safety pin to very carefully raise the barb up to about a 15-20 degree angle and try again. You may need a magnifying glass to see all this...

Once you’ve solidly inserted the wires in the inner shell, then put the plug retainer c-clip back on. Now slide the outer connector shell back over the wires down onto the inner shell and push together until you hear the click. It is keyed so it only goes one way, so if it won’t go on flip it over 180 degrees and try again.