[Gmecm] Crazy 7730 problem - random numbers for TPS & ECM very warm...

[David Allen]

Hello guys, I've got a stumper of a problem.

Just finished re-pinning a MAF ECM (old 3.8 Buick, has the 2 connectors) for 
a 7730.

I powered it up to see the data on the computer, and I get some strange 
things.
The fuel pump prime function and Check Engine light function as normal.

When first powered up, the TPS shows a seemingly normal voltage. The TPS 
reading will move with the pedal position. Then, gradually, it starts to 
read a bogus higher and higher voltage, eventually stopping about 3V, with 
no change when the pedal is moved.  Verifying with a meter, the TPS voltage 
is stable at 0.5V and does operate normally with the throttle.

The second thing is, the MAP reading is fixed at approx. 60 kPa. The MAP 
sensor voltage is correct (measured with meter) and does fluctuate with 
vacuum.

Then, the ECM gets warm, after 3 or 4 minutes. This is without starting the 
engine or activating anything.

I have disconnected everything from the ECM other than the "A/B" connector, 
and powered it up. The scan data does the same thing, TPS starts at low, and 
after a few minutes it climbs.

The TPS issue will return to normal (for a few moments) if I power off the 
ECM and power on again. The MAP never reads other than approx 60 at any 
time.

The sensor +5V reference and sensor ground are correct and never fluctuate 
even as the readings drift.

I thought the ECM was damaged, so I tried another one. It did the same 
thing. I know both these ECM's have worked correctly before.

I'm running Code59 V.23 exactly the same as another identical engine which 
runs fine.

I've used the same diagram for 2 other conversions, and they both worked 
fine. I am at a loss.

Thanks for any insight!
Sincerely,
David