1994 E320 CEL Issue

[geraniumtr]

Folks, a couple of weeks ago I noticed the CEL wasn't momentarily coming on when starting the car. Its not a burned out bulb because when I operate the push button LED diagnostic box the light will illuminate and stay on even with key removed. Pulling the fuse turns off the CEL.

The EGR valve opens and closes when vacuum is applied/released using a mity vac. The switch over valve is less than a year old as is the oxygen sensor. Car runs normally.

Any ideas.

Regards,

Peter Weissman

 

[gsxr]

If the bulb is good and CEL isn't turning on (or off) as expected... the DM (Diagnostic Module) may have failed. I'd swap the DM with the identical part number. They should be cheap, the DM's are pretty rare failures.

Alternately, disconnect the DM and live without the CEL, unless you need it for emissions testing where you live.

 

[geraniumtr]

Dave, Just an update....issue solved. After I posted I noticed slow cranking when starting and then a dead battery after sitting over night. Battery is not too old so I guessed a parasitic drain somewhere.

I figured the OVP relay was a good place to start and as it happened I had a spare. Sure enough that was it. CEL now illuminates as it should and no battery drain.

Regards,

Peter