ASR Light - HELP M.B. DOC ! - PeachParts Mercedes-Benz Forum

silv500 · #1 12-13-2005, 09:00 AM

Hi , I have the ASR problem i have read so much about on this forum. I have a 1990 500sl and it has only recently developed this fault. The strange thing is, when i slightly adjust the slack out of the throttle cable, the light goes out and the car comes out of limp home mode. Sometimes it lasts for weeks, sometimes it needs more tweaking. recently this has stopped working and the asr stays on and in limp mode. With the cable adjusted even more, the car idles too high and seems to have a mind of its own in the rev range. However with careful adjusting i can get the asr mode off and the car idling right BUT as soon as i even breathe on the accel pedal, ASR ASR !!! aaargh.

My questions are these, if anyone can help :
I have read lots about people changing the brake switch - does this seem like a suggestion for me ( i'm not sure as the accel pedal touch relights the asr )
Also, i heard something about the OVR Over voltage relay ? Reason i ask is tha my car was jump started and i think thats where all this started.

Any help greatly appreciated, as my grin is now

mbdoc · #2 12-13-2005, 09:17 AM

THAT is one of the hardest systems to diagnose due to NO computer memory.

IF the system stays in limp mode then a pin to pin is required.

MOST common failure (beside the brake lamp switch) is the accelerator potientiometer!

silv500 · #3 12-13-2005, 09:54 AM

thanks for the quick reply.
is that the part that costs $1200 ? Just my luck !

what do you mean by a pin to pin ?

mbdoc · #4 12-13-2005, 11:56 AM

Pin to pin requires a volt/ohm meter & wiring info for that system. Basicly checking for correct signals to/from computer.

The potientiometer MB part number 000-540-14-17 lists for $ 695.

silv500 · #5 12-13-2005, 10:32 PM

Thanks MB doc.
Is that the large part described here ...as an electronic throttle actuator

http://pages.prodigy.net/jforgione/MB_asr.html
sorry for all the questions

deanyel · #6 12-14-2005, 01:05 AM

You have a 1990 500SL with ASR? That's strange. What country? Is your engine a 119.960?

JimF · #7 12-14-2005, 12:59 PM

Quote:

Originally Posted by silv500

Thanks MB doc.
Is that the large part described here ...as an electronic throttle actuator

http://pages.prodigy.net/jforgione/MB_asr.html
sorry for all the questions

You can build a homebrew code reader described in MENU#2. That will allow to read what the CFI module "thinks" is wrong. I would venture a guess that you may read DTC#10?

16 pin Diag Connector
Yellow: Read data from Pin 3
Power from Pin 16; Ground on Pin 1

DTC Readout Possible Cause of Failure
1 No fault found
2 Throttle position switch; wide-open throttle fault (WOT), signal faulty
3 Engine coolant temperature in CFI control module illogical
4 Air flow sensor position indicator potentiometer current illogical
5 Oxygen sensor signal illogical
6 Not used
7 TNA- signal (rpm) at CFI control module illogical
8 Altitude correction signal from ignition control module
9 Current to EHA is illogical
10 Throttle position switch; closed throttle position fault (idle)
11 Air injection system, open or short circuit
12 Absolute pressure values from ignition control module illogical
13 Intake air temperature illogical
14 Speed signal at CFI control module illogical
15 Not used
16 Exhaust gas recirculation switchover valve, open or short circuit
17 Oxygen sensor signal wire shorted to positive or ground
18 Current to idle control valve is illogical
19 Not used
20 Not used
21 Not used
22 Oxygen sensor heater voltage illogical
23 Short to positive in purge switchover valve circuit
24 Not used
25 Short circuit to positive in start valve circuit
26 Short circuit to positive in upshift delay solenoid valve circuit
27 Data exchange between CFI control module and ignition control module
28 Intermittent contact in engine coolant temperature sensor circuit
29 CFI and ignition control module reading different engine coolant temperature
30 Not used
31 Intermittent contact in engine coolant temperature sensor circuit
32 Not used
33 Not used
34 Engine coolant temperature read from ignition control module illogical

silv500 · #8 12-15-2005, 07:48 AM

thanks JimF, thats a good load of info, I appreciate your help. I will get onto your idea. However if i get fault 10, is that the same part to be replaced as MB doc suggested or is the position switch totally separate ?

....going no where fast,,especially in asr mode !

mbdoc · #9 12-15-2005, 09:03 AM

Code reading of the fuel system is a good IDEA, HOWEVER it won't help you at all in diagnosing your ASR problem! That is a stand alone system with NO diagnostic memory!

AGAIN that is one of the hardest systems to diagnose! YOU need a good technician with good info on that system!