[FIXED] cylinder #4 fuel injector has constant ground signal

EricGoodrich wrote: "Why is there ground on the power side of the bulb?" "Is it a short to ground on the power side?" "Why isn't it blowing the fuse?"

I LOVE that green light.

OMG.. Was it possible I was testing the wrong terminal in the injector plugs as Eric had alluded to?

Well having a schematic (Thanks Chad) with the numbers marked 1 or 2 for the injector plugs and having my wife verify the colors since I'm color blind, ERIC was right, I was testing number "1" power terminals on the injector plugs all along...

I apologize for having wasted everyone's time..

Re- testing with battery connected and using test-light between + battery post and terminal "2" (ground) on the injector plugs now resulted with light ON when ECU connected and light OFF when ECU disconnected.. I'm now confident that the problem lies with the ECU and not the wiring harness. I assume I no longer need to disconnect or cut the ground wire from the ECU and test with the engine running.

Thanks Chad, Eric and all for your help...

I sincerely apologize to all for having got my wires crossed in not identifying which were the actual ground terminals "2"at the outset.. I feel like such an idiot... Again thanks to all..

A final question or two...Could anyone recommend whether it is better to get a new ECU (programmed to plug and play) or is it OK to get the original ECU repaired? I've found a number of places online that can repair ECU's. Could anyone recommend a place they've had good results with? Also, I should probably get new fuel injectors as I've read that working but bad injectors can cause the injector drivers on the ECU to go.

Cheers...

alfredo wrote: I apologize for having wasted everyone's time..

If you came out of it with a better understanding than you went into it, then nobody's time was wasted.

I'm glad you got to the bottom of it. As for replacing or repairing....I have sent modules out to be rebuilt a few different times. I don't think I have ever used the same place twice. Once, through Autozone. :ohmy: Once, from an ebay listing. And, a couple different websites. (I can't recall, specifically). Usually, though, the reason I chose rebuilt over new was because I couldn't get new. On one occasion, the module was returned to me as "un-repairable". Beyond that, I have had no bad experiences with rebuilds.

Monde wrote: Did you do the test with the car running? If you did not, you have to start the engine to see if the light flashes, which will tell you the pcm driver and the wiring are fine.

There should be no ground KOEO. If disconnecting the ECM removes a constant ground, it is safe to say the control driver is shorted to ground. The ECM should PULSE a ground only when running or cranking. It should not supply a constant ground with the engine not running. In this case, the light will not flash. It will stay lit, continually.

Be sure to check the injector for a short circuit before you replace the ECM. A shorted injector coil can allow more current to flow than the ECM driver can handle. It's a possible underlying cause of the failed driver.

Thanks..Yes will be putting in new injectors after I get the ECU repaired.. Aftermarket injectors ok?

Will post outcome after repaired ECU installed..

Then will need to deal with another issue..The TCM for the CVT also needs to be sent off for repair which has the classic PRND light flashing on dash with no reverse going into limp mode... Wish I knew all the problems AUdi's have before I got the car for my wife.. The only good thing I can say about the A4 cabriolet is that it looks nice..Oh well live and learn..

Happy to report back that all is good now.. To be on the safe side installed refurbished fuel injectors before plugging in a donor IMMO ECM and car is running good again.. I recall someone earlier posting that a faulty injector coil could also be cause of shorted injector driver on ECM.. I suppose I should change the coil as well.. Don't want to have to do this all over again..
Now need to send off the TCM for repair...Never ending on this Audi A4..
Cheers to all and a Happy New Year..