Thanks for reading you three hundred...no constructive comments! Well tonight I will remove the air bag and test the pins on the back with a multimeter to see if it will give an ohm resistance when the grounding bar is pressed in. A measurable resistance will suggest the unit is good. Then I intend to get to the multiplug behind the steering wheel and check for continuity by cutting into the wires behind the multiplug and test the resistance and integretity of the airbag connections through the multiplug. Then I will cry and consider my next option.... I read on the thread that the yellow plug in a door panel solved the issue in a car, I suspect this was part of the circuit or sensor used to measure a side inpact. Perhaps a main dealer or Merc diagnostics computer could identify where a system has failed, rather than "FRONT DRIVER AIRBAG" Any suggestions keep them coming.....best wishes Andrew.


Okay that was easy, removed airbag unit (120 seconds) tested pins properly grounded when removed. Added yellow power clip and read resistance through end prongs at 3.2ohm. So this suggests that everything is in order here and I havent blown myself up! Now I must get to the multiplug harness!!! The fight continues....

Okay getting to the multiplug defeated me...it got dark....instead I trawled through even more SRS threads and kept crossing "PassengerSide module" "Drivers Side Module" Corrosion under seat issues....I wonder if the wiring to the front air bag goes via a door control module and this is interupting the SRS module from detecting it....UMMM Do I A:Go for the multiplug or B:investigate the door module...C: replace the battery.....D:Check the wiring on the SRS module reported to behind the ashtray....E Get hold of a copy of Star/Das....all of the above!

 

Mine came on twice now with the code "over voltage to drivers airbag" but a star scan cleared it both times for me and touch wood it will stay off. My brother said he was told that the systems rely on the battery being in good condition, so i'm gonna try a new one to see if it will clear a few of my cars issues. How old is yours?

But it looks like your going about it the right way, if you can get a cheap module thats what id try,(but then i get 'p@st' off wasting money when the replacement doesnt sort it!) i would have thought the star scan would have pinpointed your problem though, either the module or a connection somewhere.
Just out of interest, how do you know your getting the right resistance? as an example On a focus with the srs light on, the crash sensor gave me a resistance of 5 ohms but it should have been 3 times that, so a new one fixed it.

 

Thanks for your comments, I watched a You tube clip that showed them testing an airbag and it was 2.5ohm, the tech suggested that a value of 2-3ohm would identify a good unit so I have assume this is a fairly standard value for a widely used product. Unfortunately I haven't paid to have a Star Scan, an independent diagnostics tech with a £1500 snapon scanner read the drivers faulty airbag code. Perhaps it was a false economy for £20.00 but he came to the house and read it twice, confirming a faulty crank sensor also so I can't fault him. The independent Merc garage and Main dealer are not very friendly or accomodating. I know it only takes them 10 minutes to cycle throught the menus and read and clear codes, but they insist it stays there all day and that makes my wallet nervous. The battery could be an issue its probably three years old...but there have not been any issues starting the car or other low voltage messages on the other systems. I have read on another forum that the main dealers have a dedicated system for fault finding the SRS circuit, perhaps every part and component is identified with a different resistance and by measuring the values an area of the car can be more closely identified. I was close to biting the bullet and buying the aftermarket Star/das, but after reading the horror stories on this forum it seems almost financial suicide, particularly if the reliability and complexity is to be believed. Lots of people seem to have purchased the chinese clone systems and then not be able to use them for a wide variety of reasons. While others have created problems rather than cure them! I like been self sufficent and understanding and fixing my cars but this SRS is perhaps more difficult than i imagined. I'm pinning my hopes on finding a break in the wiring a high resistance in a multiplug, or identifying a fault in the door control module? or corrosion under a seat or under the carpets, or a poor contact on the SRS module....its got to be worth a look..............just don't tell the 18yr old landrover the Mercs broken down or I am truly stuffed.

 

My suggestion is to get a dealer diagnosis. You're going to waste more money trying this and trying that than just getting the diagnosis. If you get the diagnosis, then decide if you want to do the repair yourself.

You've already wasted money.

 

i can understand a connection coming loose under a moving part like a seat, but when its behind a dash? Id say its more likely a module failed.
I risked the cheap clone, came with an ibm with import taxes for £360 (got 5 mercs in family so will get used).
Have a look for an independent abit further away if your locals are no good. The missus would kill me if i offered to scan yours (doesn't like me working on mine) but she's away nxt month for a weekend, so if you want to drive to Nuneaton I'll scan it for nothing.

 

Thanks Robin, that is an extremely nice offer and if you were a bit nearer I would snap your hand off, I am seriously considering the purchase of the IBM T30 Scan/Das C3 and multiplexer. Why because the local garage has quoted me £135 to read the code! Which is insane I might as well invest that into the technology myself. Even if i can't fix the SRS i'm sure it will be a useful diagnostics tool in the future to keep the car monitored, code cleared and running properly. As for wasting my money well the steering wheel clock spiral had goodness knows how many miles on it and so its one less part to fail in the future. Changing both the lower arms on the suspension myself saved me a kings ransom so i'll just soldier on and see if i can fix it.

I stripped the steering wheel back to the multiplug and cleaned all the contacts and I took out the centre console, removed, opened and visually inspected the airbag module, and cleaned the earthing bolt it grounds itself on. Contact cleaned every plug and jack in the disassembly, checked the wiring harness in the door control module to look for anything obvious and cleaned all the plugs underneath the seat....to no avail. I have purchased a T30 computer loaded with the software and the C3 equipment to see if this will give me the insight I need to check the SRS system. Any hints or tips greatly appreciated from those of you who already have the facilities to check your cars. Bought it in the Uk should get it Friday or saturday, Whole package £500. Andrew. Anyone who needs there car reading in Berkshire get in touch.

 

Update to help others who follow in our tyre treads, the "new" diagnostics software arrived as promised, fully loaded on the machine and worked out the box, plugged the computer into the multiplexer, multiplexer into the 16 pin OBD socket and hey presto...straight in, quick scan, airbag fault identified, one stored code as described, deleted code. Unplugged and started car.....NO SRS light.....30 minutes it took, absolutely delighted, should have bought it a year ago....owning and running this car is now more realistic and less of a liability. Ready to go back to the MOT center Day 7 of 10! hurray.

 

What new diagnostic? How much?

 

The only one recommend by the good people on this forum...

The old IBM t30 + installed software Scan/Das C3 I bought from EBay seller two days ago, cost Uk £515. New chinese multiplexer clone and software worked perfectly straight out the box, cannot fault it, level of information on faults and suggestions to fix excellent. It took less than thirty minutes, I could do in less than five now I know how. I might even try and fix the ashtray light I didn't even know was broken!

 

LOL. Nice!!

I got one for you to try. I could not do it on my "cheapy" x431, but maybe you can.
1: Turn on the alarm sound when you unlock/lock the doors.
2: See if you can find the option for turning on the "Auto" folding mirrors on lock/unlock or when the key is turned off. Not sure which one it's attached too.
I had to have the dealer turn number 1 on for me and number two wasn't an option for my car.

When you get time of course.

 

Won't i wear out my mirror motors and bleeper thing!!!!

Hey is it just my car or is the horn the most pathetic horn in the world! its like a comedy horn, i never use it in anger...but when i need to let someone know i'm there it's just embarrassing! This massive beast of car sounds like a noddy car I've got to sort that out!

 

Hummm, don't know. My horn sounds like a factory horn.

And it's not the horn that chirps with my alarm. I hear more of a click chirp sound now that it's been turned on.

As to the mirror. You're more or less looking to see if it's an option that can be turned on on your car. And if it shows in your instrument panel you can turn the feature on/off at will once activated by software.