1992 S500 W140 119 engine
4 week ago the engine was shaking erratic and the the RPM was jumping from near stall to 1200. Black smoke was coming out from exhaust. When i put more gas on the throttle the engine loss power and this is really un-drivable at all. I read a number of threads where it say it could be mass air flow sensor, wiring harness (engine wiring harness change 3 months ago) and throttle actuator could be the main course.
What have i done ?
Open up the throttle actuator and found the wiring insulation had gone. Replace all wiring with teflon wire as per Pete website (great website). Put back the throttle actuator, MAF and all other bit and pieces. Start the engine, it run really rough (as before) but without black smoke, however smells of unburn gas. Leave it over night and start the engine again. This time it run smooth but SRS light stays ON.
Please help how do i get rid of SRS light which stays ON.
I have a TRISCO Palm Scan (PS-411-Benz)
Thanks.

 

SRS is an Safety Restrain System - Airbags. Its has nothing to do with the engine.
Make sure you did everything correctly when you messed with the wires.
Or take the clamp off of the batery and leave it like that overnight - sometimes it helps, unless the code is stored.
if so then you will have to clear it with a computer!

 

Wires were double check and confirm all are correctly install.
Will take the clamp off of the batery and leave it like that overnight - will let you know tomorrow.
If the code is stored how do i clear it. Can TRISCO Palm Scan (PS-411-Benz) do the job?
Thanks.

 

i am not sure about your scanner but you can try. I know that you would need STAR Diagnosticto clear upcodes. but if anything, give it a try with your scanner

 

plug in the scanner, there are two codes, 139 and 03. 03 says low voltage. 139? the scanner didn't say.

 

Erased both codes, however 03 stays. Code 03 says "low voltage supply circuit 15R". Put a volt meter across the battery it reads 11.5V. What do i need to look out for?
Thanks for helping.

 

your battery is good, i am not a specialist in older models so i can't recommend anything for you here, but suggest you should find what circuit 15R is and see whats wrong with it!

 

What have I done so far?
Charge the battery and plug in the scaner. This is what i got

*LH, HFM, ME(R)
Read Code 21 ie intake air temperature sensor shorted or open CKT. Erased the code but it come back instantly. What does it mean by CKT? How do i check the air temperature sensor whether it is working properly?

EA/CC/ISC
Read code 224 ie idle speed contact switch S29/3 fault. Try to erased the code but it came back. Question is how do i check the switch if it is operating normally.

SRS system
Read code 03 ie low voltage supply circuit 15R. Erased the code and check the system again, it says system normal. Wait a while and check the system, it says system normal. Again wait a couple of minutes and check the system the code come back. Without ersaing the code and check the system again it sometimes say normal and sometimes give code 03.

Appreciate great help from this forum.
Thanks.

 

1)the only way to find out if your air temperature sensor is good is by testing it using STAR diagnostics, you will not be able to test it with your scanner. It should be located on your air inlet tube, probably before Mass Air Flow Sensor.
2)S29/3 - try to find out what it is responsible for
3) Again try to find out what circuit 15 R is and where it is located(maybe there is a fuse??)
4) try calling your local MB Service department, sometimes they are helpful and can tell you what S29/3 is and Circuit 15R