Check engine stays on without USB plugged

[zaknafein]

Hi

I wonder if you ever saw this before, I have a '92 EG with a '03 K20A2 swap using Hybrid Racing harness, car is running perfect since 2009 with my K-Pro.

However this morning it refused to start correctly, when I put the key on the check engine doesn't go off and the car starts after 15-20 turns. The engine is running really rough...

If I connect my laptop with the USB without even opening kmanager everything goes back to normal and car runs fine, no check engine, runs smooth. So I can't scan my code it disappear as soon as I'm plugged in.

If I disconnect USB, check engine stays on and car won't operate normally again. Only solution I found is running with the laptop constantly connected.

KPro dead ???

Thanks a lot
Fred

[Spunkster]

Check your grounds as it sounds like something may have come loose and it is grounding through the USB port. Do not continue to run it with the USB connected as it may do more damage.

[zaknafein]

the grounds in the engine bay or the ground wires going out of the ECU ?

[Spunkster]

First one, then the other. Check the engine bay first.

[zaknafein]

thanks a lot :D

[Spunkster]

You can also try the ECU in a known working vehcile and see if it works correctly. If it does this will tell you for usre there is a wiring issue in your car. If there is a problem on another car then the ECU, K-Pro or both are probably damaged.

[zaknafein]

Solved, there was corrosion on the ECU board, the KPro board was untouched.

Cleaned everything nice and it's working like new!

[zaknafein]

Damn, problem came back this afternoon, all ground are good...

[Spunkster]

Post a picture of the corrosion in the ECU

[zaknafein]

Corrosion wasn't really that bad, I work at a Honda dealership and my tech told me he saw really worse things working fine, we cleaned that up anyway. it doesn't seem to be the problem.

I don't have any "before" picture, but there was only a little stuff around the edges of the processors on the PRB board under the Hondata board, Hondata board is like new.

[Spunkster]

Have you tried it in another vehicle?

On an ECU with corrosion on the inside of the ECU, especially the processors, we weill not even install a K-Pro. This was installed by one of our dealers, so you may want to discuss this with them (Synoptic Tuning). The ECU will probably have to be replaced, as once corrosion starts it will continue forever especially when there is electrical current.

[zaknafein]

Not yet, K swapped cars or RSX-S are not common here in my town :P

A friend of mine is going to come tonight with his car to try

I'll talk to Synoptic, he's the one who installed it and he was really a good guy on the phone. He probably did the install perfectly, my car let a little water in once last summer, I guess it all started there....

It's really weird, was perfect last night after the cleanup and this morning I went to work with the car fine, then went for lunch and car won't start.
I can start it with laptop plugged, then unplug and go, fine until next shut off/start

big thanks for your fast answers and trying to help :)

[zaknafein]

does the same on the other car, check engine on kpro alone, no check engine if plugged to laptop, her car can't run with my kpro map it dies after starting either way (plugged or not) (she have a K24 instead of K20)

however I seen an error popup once, "daughter board communication error" on my car, I'll try new grounds and another battery on my car tomorrow, but that doesn't explain why it coded in her car without the laptop plugged...

If I start the car with the laptop on, disconnect it then reconnect, check engine goes on and car stops instead of reading "kpro connected" in kmanager...

Looks like a dead ECU to me :(

[zaknafein]

.I found in another thread that it can be battery related, I completely redid all the grounds in the engine bay brand new and got a new battery today at work

I also found you told to check A2 and A4 pins on the wire harness as they are the ECU grounds, with no key in the ignition, A4 have 0 ohm resistance, but A2 have 49.9 ohms, is it normal or should it be 0 too ?

[zaknafein]

SOLVED, was caused by the battery, seems like the negative pole was broken inside.

K-Pro is fine, car is running fine since friday morning, thanks for the help !!