01 Quest MIL ON, BUT NO CODES ARE STORED

[nichols1992]

I have a 01 Nissan Quest 3.3 the MIL is on and there are no codes stored. I have a Genesis scan tool and I've scanned it using the asian software and with a generic obdII scan and there are no codes stored. There is also another problem . The a/c compressor clutch is always engaged even when it is turned off. It runs constantly to the point where it builds too much pressure and it begins releasing refrigerant through the pressure relief valve on the side of the compressor. I've disconnected the compressor for now. I was curious if anyone knew about a possible computer update for any of this or if anyone has run into anything like this before. Thanks Bill

[MaximA32]

It could just be a short. If there aren't any codes then that's all I can think of.

[nichols1992]

Well there are'nt any shorts or opens, at least not in the a/c circuit. I checked the a/c relay to ecm circuit. With the engine running and the a/c switch on the voltage should be 0-1V, and it is. With the engine running and the a/c switch off the voltage should be 11-14V, and it is not. It's below 1V either way. I also checked the circuit for an open or short and there is neither, so I checked the high pressure switch to ecm circuit. Engine running and the a/c switched on the voltage should be 0V and it is. Engine running and the a/c switched off the voltage should be 5V and it is.So I'm assuming the computer either needs to be flashed or replaced. I can't flash the computer so I'm taking it to the dealer this afternoon. I spoke with the service manager and he's never heard of the problem either. With the research I've done on the web, posting on this forum, and talking to the dealer it does'nt appear to be common so I figured I'd give 'em a shot and hopefully all it needs is a good flashing.

[driftingmy240sx]

reprogramming is not availible to fix this issue. there is probably a bad driver in the ecm. try swapping with a known good ecm. can you communicate with the ecm and find no codes or is there no communication with it at all (if the latter the ecm is toast or the ecm relay is)

[nichols1992]

It was the ecu. Nissan wanted $1,400 for a new one. I found one for $85 at a salvage yard, put it in, and now no service engine soon light and the a/c clutch only engages when you turn on the air. I took it to the dealer a couple of days ago hoping they would try to reprogram the ecu, but they repeated everything I had done and told me it needed an ecu. If I had the capability to reprogram it, I would have tried that first. Now that I look back I would've probably spent $80 - $90 having it reprogramed, so I should've shopped a used ecu in the beginning anyway. Thanks for all your help.