No Check Engine light

[kre8tive202]

Hello every,

I need help fella's.....I have a 1992 Mercedes 500E and about 3 months ago the check engine light quit working. When I go to try to push the diagnostic button under the hood to try to see if I can even get a code, I get nothing. I live in California and need to get the car smogged for my registration renewal. I know the check engine light has to at least come on then off for it to pass the visual check. What should I check. I bought another diagnostic control module from Ebay plugged it in but no luck. What should I check next. Help Please...

 

[J-Sauce]

A morally ambiguous man might tell you that the easiest way to pass smog in your situation would be to pull the cluster and swap positions on two of the bulbs so that the cel still illuminates on startup and goes off immediately afterward. He might also advise that if you went that route, to make sure your fluids are topped off and your brake pads not worn too low.

I wouldn't, but a lesser man might.

 

[kre8tive202]

Nice....that is definitely an option

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[nocfn]

My first thought was the bulb, not to make it more complicated than it is.

 

[gsxr]

Check the bulb first. If it is OK, the DM (Diagnostic Module) which controls the CEL may have failed. DM's are dirt cheap because they almost never fail and supply greatly exceeds demand.

 

[kre8tive202]

The DM is the silver box under the passenger side floor board correct? If it is I bought on from ebay but it didnt help. Unless i coincidentally bought another bad unit.

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[gsxr]

The DM is the silver box under the passenger side floor board correct? If it is I bought on from ebay but it didnt help. Unless i coincidentally bought another bad unit.

That is correct. It's possible, but unlikely, you bought a defective unit. Have you confirmed the bulb is OK?

The next step would be connecting a digital scanner that communicates with the DM to verify it's working, and then see if there is an activation to manually turn on the dash CEL via the scanner (pretty sure you can do that, but not positive).