Thank you, sir.

One point. I think your vehicle is later than mine and does not have the KE Jetronic injection with separate electronic ignition that my 1991 car has.

Having said that, you suggest that the 'reference resistor' is that which is plugged into the ignition control module and, presumably, retards the ignition. If so, that makes sense to me as I have removed that resistor over the years in order to test the vehicle's performance and fuel consumption when using 98 (as opposed to 95) RON fuel. Never noticed any significant improvement.

So, the system might have logged the removal of the resistor as a fault.

I still cannot understand why I can't erase the faults. I did so for the auto box and it now works very well.

Oh well, As long as the thing drives well I suppose that's the main thing.

Thanks again.

RayH

One more time . . . the module has an internal failure in the onboard memory. Similar to a computer's memory stick. The failure causes the unit to register a fault that's not really there! It's that simple . . . .

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

Jim,
How did you find and test for the "memory-bit" failure inside the DI Module? Is this the same as the Ignition Control Module?

I have code 6 (Camshaft Position Sensor) which is constantly there along with hard/no start isues with random stalling in town. I leaning towards my ICM.

Over the years reading stored DTCs from many DI modules, I've found some that have memory failures that indicate a DTC but it's not a real b/c of a bad internal memory bit in the module itself.

It started about 1 year after I got the '94 S500. The DI module suddenly showed the "CKS" sensor as failed. The CKS is a non-electronic device (some wire wrapped around a magnet that measures correctly) so that showed me that a DI module can fail causing the CE ckt to light generating a DTC that is NOT real! Once the CE lamp is on, just try to pass a CA smog test. Real or not, it's counted as real!

After replacing the DI module, a few years later, the module showed a DTC = "Reference Resistor is bad". Well, it's NOT (it's there and measures correctly) but the DI module "thinks" it's bad. The good news is that the REF RES failure does NOT cause the CE lamp to lite b/c it's not an EMISSIONS related failure as was the CKS. This failure has been there for a least 13 years or more.

In your case, I might tend to believe the failure b/c of stalling, hard-starts, etc.

Hope this helps.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page