First of all, let me say that I have read EVERY ASR thread last night, about 11 pages full! Try that for bedtime reading! I guess that if you own a Mercedes, you will at some time get that problem!

My ’94 S500 ASR light started to come on about three (3) weeks ago. At first, I just could ‘fix’ it by turning the car off for 5-10 secs and then re-start.

Slowly it’s been getting worse. About 3 days ago, it wouldn’t reset by recycling the ignition. I drove the car for 5 minutes; when stopped at a red light, re-cycled the ignition. It went off and stayed off as long as I drove the car.

Symptoms:
1) Only occurs when the car is HOT, not warm.
2) The ASR light comes on, tachometer indicates 1000 rpm but can drive the car even though it’s in the Limp-Home (L-H) mode.
3) If the ASR is on, drive for 5 minutes or so, stop, re-cycling the ignition and the ASR light will go off and STAY off until I stop the car and let the heat build up in the engine compartment. If I start the car, the ASR light and L-H mode will be active but it can be ‘reset’ by driving it for a few minutes (even if HOT) and recycling the ignition.
4) It NEVER comes on while driving.

DTCs:
Yesterday I dumped the codes with an AST Retreiver Scanner:

Base Module: No codes
Diag Module: REGISTERED CODE only - Code 6 - - ISC faulty
EA/CC/ISC Module: Code 2 - - EA/CC/ISC or Contact switch M16/1s1 or Stop lamp switch.
ABS w/ ASR Module: Code 30 - - CAN bus to EA/CC/ISC faulty.
LH-SFI Module: No codes.
DI Modules: No codes

Note that the CE light is NOT on. The DM module has a registered code but no ACTIVE codes.

I removed all of the modules in the F23 box, removed the box frame itself, and inspected all of the wiring to the connectors especially to slots 4/5 (ABS w/ ASR) and 6/7 (EA). All wiring was ‘solid’.

Using an ohmmeter, the CAN bus was checked. All readings ok: 120 ohms across the bus and continuity to all modules on the bus.

After reinstalling the modules, which had all cooled down, the car was started, NO ASR lamp. Ran perfectly.

Drove it for about 20 minutes, parked it in the sun (yesterday in SD, it was 95degs). About 1hr later, I came out and started the car, ASR on and L-H mode. Performed 3) above and light went out. Parked in the garage; let it cool down overnight. Just started it ‘cold’ this morning, everything ok, no ASR.

I have my opinion as to what’s I think is bad, but would appreciate your opinions and what would you do next?

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Regards . . . . JimF
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'94 S500 Cpe

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