Howdy folks,

Working on an 87 TA with an OBDI LT1 swap, the PCM is out of a Caprice originally I believe.

When hooked up to FreeScan or TunerPro RT, the PCM is reporting a battery voltage of around 15 volts, with the key on engine off. Actual voltage will be quite a bit lower, waiting on my multimeter to thaw out so I can get exact number.

Also in TunerPro RT, when recording data there is a field called Cylinder ID, which flickers back and forth between 00 and 02. When it says 02 the data seems to be way off, this does not happen with FreeScan.

Any thoughts on why I would get a reported 15 volts, and perhaps if that could have anything to do with the odd results in TunerPro RT?

 

Tested each pin providing power to the ECM, get just under 12 volts, while the ECM is now reporting 16.

When running It throws 4 codes:
83 TCC Feedback Fault
50 System Voltage Low
77 Fan 1 Fault
53 System Voltage High

83 and 77 are not a surprise, but I don't get why the PCM seems to be so confused about the voltages.

 

Tried swapping out the ECM, gets the exact same high voltage readings. Not sure what is going on.

 

Sounds like you have something crossed somewhere with a ground or power wire going somewhere it shouldn't.

 

I'm pursuing that possibility now, checking all the grounds to see if they are not actually grounded. Haven't found any issues yet.

I did however notice that when I have scanning software hooked up, I am getting O2 voltage readings even with the O2s completely disconnected. Its reporting one O2 locked at .453 and the other fluctuating around .7. Neither O2 is connected at all, and there is no voltage at the O2 Pins on the ECM