1992 400SE W140

After clearing all my fault codes, these 2 codes returned:
Distributor Ignition (Socket 17)
Code 6 - Camshaft position sensor
Code 8 - Transmission overload switch does not close

I ordered a Camshaft position sensor made by Facet and a Transmission overload switch online at a fraction of what MB wanted.

I installed the CPS last week and cleared the code...car started right up and ran excellent all week. Yesturday it stalled on me while about to take off at an intersection, started up with extended cranking, then died when I put it in grear and wouldn't start back up again...I pushed the car into a plaza and left it there overnight. Came back today for the car and it fired right up

Checked for codes at home and had the same 2 again. Transmission switch I haven't changed yet.

Resistance on the CPS is 1360
Resistance on the CPS wire is 993

When I changed the CPS I reused the same metal shim as on the old sensor which measure in at .5mm thickness. MB has shims from .2mm to .8mm available. Could the wrong shim be in place? The old sensor measured the same length as the new one.

I'm puzzled as to why it would run for a week and then die again, resulting in the same symptoms as before changing the sensor.

Could the Transmission overload switch also be attributing to the CPS fault code? Could it be the pricey Ignition Control Module? (I've read that a faulty ICM doesn't give any fault codes).

maybe a cheap sensor? i used to sell facet in the 90s. high defect rate with caps and rotors and stopped selling them. cam sensors are more complicated to make. go with oe, if you can. i think vemo is the vendor, if you can find it outside the dealer. good luck, chuck.

Speaking of which I was going to ask about the caps, any idea when they were replaced? Had a cust. with a 400E that acted just like this, but had to be hot outside (hot in WI meaning over 85F or so IIRC). Would die, had to raise the hood and wait 15-20 minutes, then it would restart and run fine until the underhood temp got hot enough again. Was OK at higher speeds, even in town as long as traffic kept moving say 35-40 mph, but in residential areas it would do this.

__________________
Click here to see the items I have up for auction at EBay

Click here to see a photo album of my '62 Sprite Project Moneypit (Now Sold)

I've had to replace the engine wiring harness to repair a CPS problem on 140 cars before. If you can get the diagram and ohm out the sensor while wiggling the harness, it should show if its a problem.

__________________

90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

porkface,
It could be a cheap seonsor, I called MB today and it was $270 here in Canada Special order too!
The one by Facet I bought was only $37 from a US supplier.
Is there any way to test it besides the resistance? My old sensor which is OE has a resistence of 1050 vs. 1360 of this "new" Facet sensor.


Gilly,
Rotors, Cap, Ignition Coils and Wires were changed about 2 years ago.
Sparks were changed last year.
MAF was changed 2 months ago.
These symptoms occur sometimes when the engine has been siting overnight or after warmed up. I find the temperature has no affect on how it wants to act that day.


duxthe1,
The wiring harness was changed back in approx 2007. The resistance on the CPS wire measures to spec on what alldatadiy states.



When I cranked the engine today, it fired right up. I let it idle for about 5minutes and it died on its own. It started back up, while running I pulled the wire off the CPS and no change in behavior, it continued to run. I then started and idled it about 5 times in a row for 1min each without any problems. Came back in 10 minutes and it wouldn't start

I leaning toward the ICM, since I don't see what effect a bad CPS would have on stalling upon initial start or after a 10min drive like I experienced 2 days ago at a busy street

I cut open the insulation on the TBA wires and they were all intact without any cracks.

Anyone know how to test an ICM?? Besides taking a gamble with a "working" one from eBay.

Is it Ohms?
I think either Alldata is wrong or you mis-interpreting the spec. The wire resistance should be 0 Ohm

This is under Electrical Specification on ALLDATA:

CAMSHAFT POSITION SENSOR
Sensor resistance 900 - 1600 Ohm
Insulation resistance >200 kOhm

And yes, my electrical knowledge is limited, so I'm more than likely reading something wrong. How do I measure the Insulation resistance?

The resistance of 993 Ohm is on the wire I got when I measured between the 2 wires at the conector end that hooks up to the CPS itself.


Thanks to Jim's site, I have found out that 4 signals go to ICM and are split between the two 8-pin connectors on the ICM.

On the 1st 8-pin connector:
pin 5=negative, position sensor/cylinder detector
pin 8=signal, camshaft position sensor (L5/1) output

On the 2nd 8-pin connector:
pin 1=signal, camshaft position sensor (L5/1) input
pin 5=ground, camshaft position sensor

Can anyone shed some light on my limitied electrical knowledge and advise what readings/tests I should perform

Ok so I believe I've been measuring everything correctly now.

I read the resistance of the wire between the signal connection at the Camshaft sensor and A2 Ground terminal (the connection that goes to A2 on the 8-pin connection to the ICM and got the resistance of 995ohms which is the "Insulation Resistance" and within spec as per ALLDATA).

myarmar,
The resistance for the wire from the CPS to where it connects at the ICM is 0.40hms on both signal and ground. This seams normal?

I took the ICM out and found almost no thermal paste on the rear I'm assuming that can't be good.

Does anyone know how to test the ICM? I got readings of the resistance between the 7 common ground connections as low as 0.6ohms (EZL/AKR trimming plug Ground TO Camshaft position sensor Ground) to as high as 15.0ohms (Crankshaft position sensor Ground TO Camshaft position sensor Ground).

Don't know if this means anything, but I'm hopping someone with electrical expertise can shed some light.

I figure I'd post the resistance readings measured from B5 (Ground, Camshaft position sensor) on the 8-pin connection on the ICM to the other 6 grounds on the ICM.

This is my ICM layout. Thanks Jim!
http://www.k6jrf.com/MB_DI.html

B5 (Ground, Camshaft position sensor) TO (Ground, Crankshaft position sensor) = 8.6 ohms
B5 TO Ground, EZL/AKR trimming plug connector = 1.0 ohms
B5 TO pin 1 Common ground on 3-pin knock sensor connector = 7.3 ohms
B5 TO A2 (Ground terminal B1) = 0.4 ohms
B5 TO A5 (Negative, position sensor/cylinder detection) = 7.0 ohms
B5 TO B6 (Ground, data line) = 0.8 ohms

No, the spec is more than 200 KILO ohm = 200000 ohm you reading is only 995 ohm. Are you sure it's not 995 kOhm?
Yes

Remember the brand of caps/rotors by chance?

__________________
Click here to see the items I have up for auction at EBay

Click here to see a photo album of my '62 Sprite Project Moneypit (Now Sold)

I can honestly say I don't think I'm measuring the insulation reaistance correctly.

I did one more test from ALLDATA which said to test voltage at the Camshaft Position Sensor while at idle...is said it sound be >0.3V at idle and increase with higher rpm's...I did not have any Voltage at idle and no increase with increased RPM's???

Caps & Rotors are Bosch.

You need to set meter to Volts AC

With my luck I'm probably measuring that wrong too.

But what really puzzled me, is I left the Camshaft position sensor disconnected & tried to start it. It cranked a second or two longer & started right up

I did change it to Volts 20 on the digital multimeter. I checked that it was working correctly by hooking up the battery leads & at idle got 16.2 Volts.

Is this >0.3V suppose to be present at the wire comming off the ICM to the CPS?