Does installing a used PCM require it to be flashed? I've been told it should work fine as long as battery is dis-connected prior to install. I've also been told car will not start until PCM is "flashed" due to installing in different vehicle.

Main reason I'm replacing is because AC compressor will not kick on after servicing. Bought Civic used and AC pressure was non-existent. Relays and compressor checks good.

Thanks.

 

Generally, yes.

This is false.

This is true. The immobilizer needs to be matched between the key and the ECU. (pcm) If they are not matched, the car will not start. This is why people need to have used ECU's reprogrammed to match their key. If you can manage to get the key, ignition switch and ECU from the same used car, you won't have to get it reprogrammed.


I doubt the ECU is the problem. Have you checked the pressure switch? Checked for leaks? Does the blower motor run at all?