PCM troubles

[MICHAELSILVTYLER]

I have a 1993 6.5 Silverado with 4L80E transmission. i have had intermident shifting problems.

indicators: speedo erratic, fuel gauge erratic.

i finally found that if i temporarily earthed the PCM the tranny would shift, the speedo would work but the fuel gauge would go the full empty position plus!

I installed a permanent earth wire. now no shift?

does anyone know if this sounds like a PCM failure?

[gmctd]

The problem is electrical in nature, more than likely not the TCM, as indicated by the gages\instrument panel symptoms.

Try R&R'ing all engine and transmission harness connectors, including the large connector on driver's-side transmission case.

Check for oxidation\corrosion - clean where required.

Remove and clean all harness ground connections to engine block and body.

Clean battery connections at Positive and Negative terminals.