case830

Hey everyone, Im new to these forums and i am stuck. Ive not been beaten by many things but I'm throwing the towel in on this one. I purchased a 2005 civic LX with a blown head. Easy enough or at least was supposed to be. I replaced the head, water pump, timing chain, etc. everything you should do when your that deep in the engine. I put it all back together and go to start it and the engine cranks perfect but wouldn't start. The immobilizer key was flashing on the dash and no audible noises were coming from the dash, truly indicating to me that the ECU seemed to not be communicating. Fast forward now, I found that the fuel pump and ECM relay behind the glove box weren't powering up and i had no diagnostic communication. I trouble shot the issue and have come up dry. I have checked and rechecked the ground on the t stat housing, the alternator bolt, the fuses, power to and from fuses, etc. IM STUCK and am way over budget on this car and now need to at least finish it. I have tried 3 different used ECM's with no luck. Last thing i did was replace the multiplex fuse box under the steering wheel.I was hopeful that this was it…..nope, same symptom. On a whim i put the original ECU back in and to my surprise the car recognized the key, and the tone on the dash did the audible beeping to let me know it was ready to start but…it didn't. It would crank and no start, the fuel pump or main run relay weren't powering up. However it proved that the multiplex unit was needed. i still don't have any communication with the diagnostic plug and am at my wits with this car. Any and all help will be greatly appreciated!!!

BrotatoChip

Did you have any communication with the other PCMs? It will never start with a different PCM unless you programmed the key into each of them. But if communication was there with the others that may indicate the original is fried.

Others here may be more help on this issue.

case830

case830

anyone have any idea or able to help point me in the right direction. Thanks to all that can help!

ezone

Only the original PCM will start the engine, unless you can program the immobilizer to replacement PCMs or you got the matching ignition/immobiCU/keys from the donor car the PCM came from.
Any replacement PCM you plug in will not start the engine until programmed, but you should always have scanner communication if it is good.

Original PCM:
Does the check engine light work at all?

Check ALL fuses in BOTH fuse boxes
Check for ground on terminals 4 AND 5 in the OBD plug


Check your car with a completely different scanner.
Check your scanner on another identical Civic
Try the SCS method for flash codes

Check continuity of the comm network between PCM and OBD plug (K line).
Check female terminals in that OBD plug for lost tension (lost contact with male pins when scanner is plugged in)





At some point it ran good enough to self destruct the engine.
Got compression? Correctly timed cam/crank?

Wait, what kinda car is this?