PCM Diagnostic Issues

[micah8719]

I have a 99 Vortec 5.3 that I put into a 92 Chevy C1500.

Wiring-wise, I'm about a week from finishing, but today I decided to check the PCM. I ran all 4 PCM grounds to a ground source, both PCM orange constant battery hots straight to the battery, and both PCM pink key hots to ignition.

I then wired up the new ODB2 port up, but both scanners I used to read the computer says "No communication..."

Here's how I have it wired (which I know is correct from everywhere else I've seen):

PCM Blue connector - Pin 58 (Serial Data) to pin 2 on OBD2 connector.
Ground to pins 4 and 5 to OBD2 connector.
12v hot to pin 16 on OBD2 connector.

I know that the computer is getting power because once the ignition key is on, I get hot coming from the fuel pump relay wire coming from the PCM. But, what is strange is that instead of cutting the fuel pump off (which I have a test light standing in for a fuel pump until I get it wired) after 2 seconds, it just constantly flashes my test light very fast and never stops.

So, I have a fuel pump wire coming from my PCM that never goes off after 2 seconds like it should and just continues to pulsate, and I have a diagnostic port that has no communication. Can anyone chime in with a suggestion? Thanks in advance.

Oh, and I'm not hooked up with a battery, I'm actually running my 12v car battery charger instead.

[farmtruc]

Make sure the PCM is getting at least 12volts , verify this with a meter.

If ur noticing a wierd issue like the fuel pump output from the PCM, it might just be a bad PCM.

The battery charger shouldn't make a difference, but try using s cleaner source for power like a new battery.

Last thing, be sure the wires are measuring correctly with an ohm meter.

[PitchBlackC3]

You shouldn't run the scanner on a battery charger only. You need a battery hooked up. You can damage the scanner with the pulsations from the charger. Don't do this with HPtuners or EFIlive or you will be buying a new interface.

[farmtruc]

oh, you're using the charger alone? i thought you meant using a charger to keep the battery alive.

[micah8719]

So yeah, the charger alone was causing the problem. I hooked up a battery and everything worked flawlessly. Later found out that the battery charger itself was bad. Anyway, thanks for everyone's input. I appreciate you guys!