independent says Bad ME1 module

[hpinfo]

I just bought an out of state 1997 E420 sport (sight unseen) and after it rolled off the truck, I noticed the CE light was on (the seller of course failed to mention that small detail.) I read the codes with my BR3 OBD2 interface and came up with P0130, P0136, P0150, P0156 - all four oxygen sensors. Reset and drove. 2nd driving cycle CE back on. Took to shop I have worked with before, same codes. On the lift it is obvious the lower two oxygen sensors are new, upper two are not. (one of lower two appears to be the wrong sensor as the wire is too long, but tech says they all work the same - no problem.)

Tech replaces other two sensors and also notices the passenger cat appears to have been split open and re-welded (maybe nothing inside?) 2nd driving cycle CE back on. Back to tech who takes car to fellow tech with SDS machine. I get FOUR page printout of stuff, everything from 'alarm activated by brake pedal' to 'occasionally altitude correction' but nothing looks too serious. My tech isn't up on reading the printout (not his machine) but when I look at it, only five of the items are printed out as a black box with white writing (what does this mean?) they are P0130, P0136, P0150, P0156 (as before) and B1438 multi contour seat air demand too high (fixing the leaking hose to drivers seat this weekend). Tech tells me ME1 unit is toast and needs new one ($1600). Strangely, the car runs GREAT - strong acceleration, smooth idle, no problems. It does seem to be running a little rich, by smell, but not horribly so. Also mileage is not that great - maybe related?

Is there any way to further diagnose this problem? Can the ME1 be sent somewhere for repair? Could wiring external to the ME1 cause this? If I was able to find a used one, does it have to be recoded in order to work or is it 'plug and play'? Would a 1997 S420 ME1 work or is it specific to the W210.

As I just bought the car, I really do not want to throw almost 2 grand at it immediately - Especially for something that won't make it go faster or handle better. I would greatly appreciate some experienced assistance on this matter.

[hpinfo]

Do any of the computer tuner shops actually sell you a new one, or are they all just reprogramming my computer (for $ 2000), like Renntech? The module cost would be easier to swallow if there was a noticeable performance improvement.

Have been hearing from techs that after 40 starts, the computer "marries" the other computers in the car and cannot be swapped to another car, is there any truth to this? How are the tuner companies able to do what they do if the computer is set in stone like that? One would think that if all the performance parameters can be read and changed, any stored information about the other computers could be cleared too.

Hoping someone out there knows the answer.

[olpos]

there are a lot of 02codes but not many class's of codes
sach as lean code

1 lazy code. most likley correct, check for vacuum leaks 80%?
2 heater code - easy d.i.y, obd2 is olmost always right on this one,check 02 is it tight? to the exhaust and the plug. putting new ones in will almost always be the answer. 95%?
3 lean bank code. if you have this code look for vacuum leaks.if you have lean bank codes on both banks, your problem is around the throttle body area. this leads up to mas air flow. this is one part that controls both banks for mixture codes. lean or rich.
it is also the hardest one to get diagnoised.
may be cheaper than a bunch of 02's
were they lean bank codes?
rich

[hpinfo]

The code is "circuit malfunction" on all four sensors. BTW, also found out this weekend that the cruise control is not functioning, all I get is a little 'blip' of the throttle when the lever is pushed. Do you know if the ME1 module also handles the cruise control?

I have found a used module, MB number 021 545 20 32 (diagnostic version 0/02) for $500. Now if the modules are no good in a different car after 40 starts, why are they selling it?

[///alpinepower]

hmm...
before you do anything (like spend money), make sure the cats work. sounds like they are gutted. And make sure the O2 sensors are real. they might be sims.

[stevebfl]

The power for all the O2 sensor heaters all come from the Z7/39 connector sleeve which is powered by k9 relay of the K40 relay module. The power comes from one of the fuses on top of the K40. The K40 is located in the electrical center on the right side of the engine compartment (pass side). The box top comes off with some screws and the K40 is to the front and has a number of fuses on the top.

If the circuit is out and all the heaters are dead you may get a performance code quicker that a heater code.

[hpinfo]

I checked the fuses and they were all OK. While I had the box open, I took a look at the allegedly bad ME1 module and noticed that the right side (closest to the fender) connector was missing its metal bale. The left side connector had its bale and looked OK. There was also red electrical tape on the bunch of wires coming out of the bad (right) one. I removed the tape and also the black plastic cover of the plug, which I think was originally glued to it but now is loose.

Under the cover, I found two unions.

First one looks like it might be factory and is one green coming from the plug crimped to four identical green wires going into the bundle. The crimp looks like a vacuum port plug and is yellow. There is a strange amount of slack in the four geen wires though, as all the other ones run straight to the plug with no slack. Could these four be related to the four O2 sensors?

Second one is obviously NOT factory, as it was wrapped in the same red electrical tape as the bundle was. Took off tape and found a badly soldered (but probably solid) union between a red/green stripe wire coming from the plug and two identical red/green stripe wires going into the bundle.

Someone has definitely been in there, messing around for some reason. Is there normally any splices in the bundle under the black plastic plug cover? Would this show in any of the parts or service info? I am now hopeful that something external to the ME1 module is causing the module to look bad to the SDS. I just need to find out what the wiring looked like originally, and how to trace these suspect wires. Would this info (very detailed wiring diagrams) be available somewhere?

[hpinfo]

Is there a good source for DETAILED wiring diagrams that would include all wiring into the modules?

[stevebfl]

The absolute best wiring diagrams that exist are on line at www.startekinfo.com it will cost you $25 for a day and you should be able to get more than you need in that time.

All forms of writen diagrams would have you lost. I spent about 15 minutes trying to find what powered the Z connector I mentioned and I basically knew where it came from and I thought I knew the diagrams. I had to search out the K40 relay and knowing that was where it was I found it. Online there would be a link at the node Z 7/39 taking one to the next drawing or to a number of orther possibilities like color pictures of locations, legend information, and rarely some technical theory.

The drawing online are also in color so following a wire is made easy.

I thoroughly recommend that everyone with a 98 or newer car view this site on a day you wish to invest in your car. There is an amazing amount of info there, basically everything I would have to work on cars. So much that you will never understand all thats there in one day.

If you go there for wiring diagrams be sure to read the specification list in the menu (left side). Basically telling one the type of computer etc. There are three files/programs that must be installed to do everything. You must have adobe for the WIS but you must load a file with a yellow icon (program escapes me) to view the wiring diagrams, I had to get tech help the first time as I'm not to computer literate (took a week and they did give me three days..... so maybe you should do it my way..)

[hpinfo]

Thanks for the info on wiring diagrams, I will check that out as soon as I get a chance.

I stated earlier that the cruise control didn't work, well thats not entirely true. Last weekend I found that the cruise DOES work, but only at 48 mph and below. I tried stepping it up slowly from about 45 but once it hits 49 mph, it shuts off. What could be the cause of this symptom?

Having put a few tanks of gas through the car, I now have an idea of mileage. Back and forth to work (95% CITY) I am getting just over 17 mpg, and that includes quite a bit of new car leadfoot driving. Last weekend, I drove to the beach (round trip about 300 miles) and got 22.7 mpg. This included 45 minutes of stop and go freeway traffic and one sustained blast to 100 mph on a two-lane for a speedo check. BTW, 100 mph indicated = 96 mph actual on GPS.

I've read a few posts about mileage and mine seems to be fairly decent in comparison. If my engine module is in some sort of default/not working mode, shouldn't I be getting worse gas mileage?

Also, and I know this is a stretch, could someone with a 1997 E420 please remove the black shield (about 1.5" x 3") over the top of the plug closest to the fender (on the ME1 module) and see if there are any factory splices? Specifically on the wires I mentioned in the earlier post. If possible, a picture would help. I don't know, but it is probably unlikely that startekinfo.com would have a picture of the wiring UNDER the plug cover - Isn't it?

[hpinfo]

Anybody have an idea on my speed-related cruise control problem? 48 mph and under = works perfect, 49 mph = doesn't work at all.

What does speed have to do with any of the parameters for functioning of the cruise control (other than minimum speed - which I think is about 23 mph)?

[stevebfl]

Could you have a tire size irregularity?

[hpinfo]

The car came with 17" in the front and 18" in the back. tire sizes are 235/40-17 and 235/40-18. Using an on-line tire size calculator, that adds up to a total difference approaching 4%. Do you think this could be the problem? What system/parameter of the cruise control is being influenced by the difference?

I am planning on replacing the tires eventually with 235/45-17 (stock) front and 265/35-18 back (the height is almost identical.) The rims are staggered width and the rears are WAY to wide for the 235 width tire - the edge of the rim is out past the side of the tire. It has already been curbed a few times and even being careful, I don't trust myself not to do it again.

[hpinfo]

Back on the subject of the computer, I just got off the phone with Bob at Beckmann Technologies Inc (800-742-1021), a company that repairs and sells Mercedes engine computers (even the new ones, and at a considerable discount.) During our conversation the subject of O2 sensors came up and I mentioned that one of my post-cat sensors appeared to be the wrong one (too long of a lead) but that my IT said it was no problem.

Bob informed me that it actually is a problem as the ME ECU cars must have the correct O2 sensors installed, if not the one wrong one (something different in how it grounds and the reference voltage) will "take down" all the others and indicate a circuit malfunction on all four. He stated that he has seen this problem more than a few times on ME ECU vehicles.

He recommended unplugging the wrong one and resetting the system with the OBDII device, which I will do first thing when I get home tonight. Hopefully this will result in only one (1) O2 circuit malfunction code, not four (4) as is now indicated.

Also plan to do much finger-crossing, praying, etc.

Bob at Beckmann also said that it is a known "fix" (NOT) for people to adapt the wiring to the ME ECU so that power comes from a switched circuit not a continuous one. That way, when the car is shut off, power to the ECU is also disconnected, erasing history and resetting the cycle counter. This is to prevent the check engine light from coming on, in order to pass emissions. This may be what was done (at one time, now reversed) under the plug cover on my car, but I will have to research the wiring diagram to make sure.

[hpinfo]

Changed out the wrong O2 sensor and like magic, the four bad sensor codes are gone. Now, as I expected, the only codes I am getting are for catalyst performance below specs. This is because they have nothing inside (I'd bet money.)

Moral of this story - All O2 sensors are not created equal, regardless of what my Independent Tech says. I'm sure he would have eventually found the problem, after taking $1600 of my money for a new computer that would not have solved anything. I wonder if the dealer would have know?

PLAY IT SMART - ALWAYS RESEARCH THE PROBLEM YOURSELF!!!! DO NOT TAKE ANYONE'S WORD FOR IT BEFORE YOU DO.

This forum is probably the most valuable tool in any quest for MB knowledge, I don't know what I would do without it. Thanks to all.