PeachParts Mercedes-Benz Forum - View Single Post - Retrieving Pre-OBDII Diagnostic Data From ’94 SL500

MB-Dude · #9 10-26-2007, 10:17 PM

Thanks Jim for the reply - especially for providing the order of the control modules.

When I press the Diagnostic Button, the LED does NOT light at all. In fact, at first I thought the LED may be burnt out. I will try it again tomorrow, using some longer wait times and hold-the-button times; different combinations based upon your idea of longer sync time needed.

Also, I swapped the battery between this car and my '79 240D. Ironically, they use the same aftermarket battery. After 3 engine starts today (after the battery swap), the CEL has not stayed lit. One of the things that always stuck in my mind (and this will sound crazy) is that whenever the car would start, I could 'sense' that the CEL would stay on. This is because I could perceive an ever-so-slight change in the sound of the starter as the engine cranked. My electronics background tells me that... maybe... I have a marginal cell in the battery that fails periodically/occasionally; especially under load – such as under starter load. In my case, the CEL only latches on during engine start – never during operation/driving. Thus, the reason I asked question #3. And remember, my CEL problem resets simply by removing the negative battery cable – this is not considered normal for the CEL. Please correct me if I am wrong on that point.

I'll report more tomorrow as I continue testing. Again, thanks to all.

Cheers,
Jeff