HELP!!!.
My ASD warning light (300E ' 87) is on all the time, it suddenly came during driving. I have tested the following:
Front wheel ABS-sensors is reading approx.: 20 kOhm. Diffential sensor approx.: 7 Ohm. All measured when car is parked.
I have checked the overvoltage relay and secured voltage (klemme: 87E, 87L) is 13.8 Volt on the socket of the ASD-ECU. I have one strange voltage of approx.: 8 Vdc at one of the pins in the ASD-ECU wireing-socket. All this is measured in idlespeed-mode with the ASD-ECU dismounted.

Can you help me coming further in the fault finding proces. If anyone have a wiring diagram (or timing diagram) for the ASD connections I would be very happy, then please mail me directly.

Regards

Thomas Vilhelmsen
B.Sc.E.E

If the diff sensor is at 7 ohms, that is a very low resistance for a sensor. Is it worn through or touching bare metal anywhere?

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Sorry! Under the dismounting process i discovered that the measure on 7 ohms apperently was for the solenoid for the hydralic. The diff-sensor resistance is 680 ohms. I tried to drive with the diff-sensor disconnected, this will turn on the ABS warning light. Conclusion must be that the sensors work fine.

What is then left, are there any contacts related to gas-/brake pedal?

Don't quote me on this, but I think the brake light switch is a part of this system and can malfunction. A tech near you should be able to retrieve codes and give some help on this subject.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

I'm not so good at sending my car to a mecanic. I got in contact with a list member who was able to tell how to build a code reader and how to interpret the codes.
My ASD-ECU had error code 3 (Stop light Switch). I have been resetting the ECU and it is now error free.

Next time the error occurs I will change the switch.

Thanks Rolfe.

Regards

Thomas

Thanks for the feedback!!

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

just for the record, ASD stands for the locking diff. (on later models), I believe you are working with the ABS (anti-locking brakes). To many darn acronyms, try ABS, ASR, ETS, ESP, SRS, ACC, AC and 3-4 pages of them in the DM.

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No i'm working on the ASD. My ´87 is equipped with ASD and ABS.