My 1995 E200-124 Auto has an illuminated SRS warning light.

My independent specialist has performed the following tasks: -

1. Tried to run an initial diagnostic check but was unable to retrieve the relevant error code(s).

2. Tested the driver’s air bag.

3. Checked the seat belts.

4. Checked that the clock spring is functioning.

5. Changed over the relevant control unit from their own donor vehicle. The control unit taken from my car was found to be in perfect working order, whereas the other unit tested in my car did not extinguish the SRS light.

The only suggestion left on the table is to get a dealer to manually check the wiring, but Mercedes-Benz refuse to provide an estimate of the cost involved, which is likely to be enormous; a ludicrous idea given the residual value of the car.

It is my belief that the reason the fault will not reveal itself is because the current diagnostic software used (Star) is a digital package and, therefore, completely unable to diagnose the analogue system in my car.

Read the following extract: -

Problem: Is the module digital or analogue?
Chassis Affected: 1992-1994 W124, W140, R129, and W202

1. Between 1993 and 1995 production dates, Mercedes-Benz models had a mix of some digital and some analogue modules on the same car.

2. Technicians should be aware that these cars might have a 38-Pin digital connector, or an 8/16-Pin analogue connector. A 38-Pin Connector does not guarantee an all-digital car.

3. If In these cases, analogue diagnosis is still required through the 38-Pin connector or the 8/16-Pin analogue Connector for the analogue modules.

4. Not all cars are affected.

Analogue or Digital: Airbag

1. All digital from 1994-1995; but finds only one fault at a time, just as 1988-1993 analogue cars.

2. Clear each fault before testing for the next fault.

3. Test as analogue first, then digital, on pin 6 (16-pin) or pin 30 (38-pin).

In a nutshell, it seems that the current MB diagnostic software has not been ‘back-engineered’ to deal with older models and the original (Hermann) package that was designed to work with the 124 Series no longer exists.

I need to know from anyone who has suffered from this problem in the past and what other possible remedies are available.

Finally, I'm no expert in these matters, so please use layman's terms.

 

I am unsure of the later W124s, but the older ones used a pulse readout system for fault diagnosis on several control units (including SRS). I don't know a whole lot about the Star Diagnosis tool, but it might just be for the modern OBD II-compliant systems. You need a pulse reader/counter to retrieve fault codes from the SRS control unit.

Also, the driver airbag does not use a clockspring; it uses brushes.

 

My vehicle is fitted with a clock spring.

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They started being used when air bags were put in the steering wheel. The old brass ring with a copper brush just wasn't reliable enough for such an important device as an air bag.

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Your comments about the pulse readout system were interesting, but I need more information on how this works in practice. Do you know where I might find such data?

 

I had the same problem on my car 4 years ago. I took it to the dealer. They told me upfront that initial diagnostic would be 1 hr labor =$85. They were able to diagnose the problem correctly in less than 1 hr(bad control module in my case).

 

The local U.K. MB dealer will NOT provide me with an estimate for the work involved. Instead, they want the car for two days minimum which, at UK£77.00 (+ 17.5% tax) per hour for labour alone, would leave me with an astronomical bill to pay.

Even worse, Mercedes-Benz UK are supporting the dealer by suggesting the same remedy (manual wire checking)!

Can you tell me exactly what your dealer did to rectify the problem?

 

The fault codes are read using a pulse counter (commercially available) or an LED. It's basically a blinking-code system. Example, if the LED blinks 5 times, that means code 5, driver seat belt. The connections for pulse readout are in the engine compartment, usually near the passenger-side firewall.

I can look into the specifics for your vehicle later tonight. However, my service manuals might only cover US models. The E200 is a Euro model.

 

I believe that U.K. and U.S. cars have diametrical layouts.

With my U.K. version, for example, there's a 16-pin diagnostic box on the left side (assume you're standing in front of the car) of the engine-bay, located behind the firewall and to the front of the brake fluid reservoir. The sockets are very clearly marked in white 1 to 16.

With a U.S. spec, isn't the same box found behind the firewall (on the right) in front of the battery?

Btw someone kindly sent me the specs for a LED tool (not through this forum). Problem is I don't know the first thing about electronics.

 

The electronics are pretty much the same, however, I just need to find the "equivalent" U.S. model to which to refer in my service literature.

 

Will all owners of 124 Series Mercedes-Benz please take note of the following extracts from a letter sent to me by DaimlerChrysler UK Limited.

 

A full analogue diagnostic has now been authorised by Daimler/Chrysler UK, to be performed on 19 Feb by my local MB dealer.

Watch this space for the results (assuming they can extract the pulse or 'blink' codes).

 

I'll be watching. I still don't understand how they can make this out to be such a big deal