Is there any way to test a pcm for a 95 z28 with an lt1? Im trying to diagnose a hard/no start condition on my car. My noid lights are telling me that my fuel injectors arent getting any pulse, but occasionally some of them do. With the key on and engine off, i have about 11 volts at both sides of each injector, but not getting any pulse from the noid lights when cranking. Sound like a pcm issue? Im very puzzled, and its driving me crazy! Any input would be great, im fresh out of ideas. Thank you

 

Blackhawk, you need opti pulses to the PCM to pick the injectors (Injector fuse supplies +12 to one side and the PCM grounds the other side to pick them). If you are seeing the Tac move, with low 200-400 rpm during cranking then the opti pulses are reaching the PCM and it is basically functioning.. You also need the 50HZ signal from the Theft Deterrent Module (TDM) to the PCM to allow the injectors to pick. Are your fans running after it starts, this indicates a SES failure that could be opti . Does the security lite stay on ?.

 

My fans actually run all the time when ignition is on. I guess the previous owner hard wired them to ign, because i can pull all the fuses and fan relays, and they still run all the time. I replaced the opti about 2 months ago, and i just checked the ign module connector for signal from the opti and i believe it was about 3 hz while cranking. The strange thing is when i unplug each injector and plug in the noid light, it takes about 30 seconds for the light to start flashing. I can run the car for a while, then shut it off and it may or may not restart. Ever hear of anything like this? And how can i check the TDM? Security light is on while cranking but goes out when and if the car decides to run. Thanks for your help.

 

I hope the previous owner installed a relay for the fans, they draw a heck of a lot of current to be wired directly to the ign. If you turn key from off-on the PCM will run the fuel pump 3 seconds and the TDM will lite the security lite for 5 seconds. Try this without starting the car, it will also lite for 5 seconds even if it starts. If the lite does not go out then the TDM has detected a bad or missing key pellet will not sent the 50-HZ signal to the PCM to pick the injectors. The TDM then locks up for 5 mins with the sec lite on before you can retry. If this isn't it I'm running out of ideas