DME Not Registering O2

[llll1l1ll]

'88 325is here with a 173 DME

Really I'm just curious about this little problem I have: it seems my O2 sensor is not registering with the DME. I disconnected the O2 sensor and the CEL did not come on and the car ran the same. I reckon if I just put a new O2 sensor in it might "fix" this problem, but my DME does not do any stomp-code testing, either.

I'm just curious if anyone has any thoughts on this. Sorry if the post seems pieced together, since I'm a bit hungover at the moment.

[jlevie]

A 173 DME does support the stomp test. But that will work only if the TPS is good and both the idle and WOT switches are seen by the DME. My guess is that the failure of the stomp test to work is that the TPS isn't working.

Does the CEL light come on when the ignition is switched on before starting the engine? If it doesn't the bulb could be burned out.

[llll1l1ll]

THe TPS is brand new. The thing is, when I do the stomp test it just blinks once and that's it.

Yes, the CEL comes on when I have the ignition in the on position.

After further thought, I'm thinking it might be the DME. I could switch in my old 153 and see what happens.

[jlevie]

A 153 DME doesn't support the stomp test, so don't expect it to work. The TPS could be new, but not suppling both idle and WOT switch signals.

The TPS must be adjusted so that the idle switch closes when the throttle stop is 0.020-0.060" off the stop screw. Then the pedal stop under the accelerator pedal is adjusted until full application of the pedal just brings the throttle body to wide open. If the bushing in the throttle rod behind the pedals are worn or missing, full application of the pedal may not yield full throttle at the throttle body.

It is also possible that you have a bad DME.

[llll1l1ll]

Even if I just manually work the throttle body it yields the same result. I think I'm going to go on bad DME for this one, since I did buy my current 173 used.

[jlevie]

Have you verified (electrically) that both the idle and WOT switches work when the accelerator is moved from idle to WOT?

[llll1l1ll]

I have not, since I don't have a multimeter and I have very poor electrical skills. I mean, I know that even though if I buy a part new, it could still be bad.

Perhaps there might be a short somewhere in the connection?

[jlevie]

Obtaining a DMM and learning how to use it will very rewarding in the long run. With one you can answer both of those questions.