Fried PCM from tearing VSS wire?

Billy_lanche · July 2, 2020

Hi all, wanted to run this past you guys to see if it makes sense. I'll try to be brief.

Bought an beater 2002 Avalanche with a bad tranny. Rebuilt the tranny myself. Excited to give it a test drive so slammed it together "enough" to give it a quick spin. Within 5 secs of driving I lost my speedometer. Looked under the truck and realized I tore the speed sensor wire because it was dangling and got spun up in the front driveshaft.

So I "lineman's spliced" the wires, soldered and heat shrinked. Still no speedometer and now it will start in 1st gear and hard shift into second around 3500rpm and will stay in second for the remainder of the drive.

Now I've read that those are the symptoms of a bad VSS.

So, I dug in. Hooked up my scan tool, showed 0mph while driving. Tested the VSS. Around 1400 oms. With the rear end jacked up and wheels spinning it was reading around 5 volts. Unplugged the red plug on the PCM and ohmed the 20 and 21 pins to the harness near the VSS to see if there was any shorts. None found and also ohmed both pins to ground to find a short. Also check the 'Brake' fuse. Everything tested good. Finally I bought a new VSS for $hits and giggles to see what would happen, no change.

So do I buy a new PCM?

I was thinking about getting a tuned one off ebay with VATS and the other stuff already deleted. At $130 that's pretty hard to beat.

What do y'all think?

davester · July 2, 2020

I would suggest first testing the wires for continuity between the pcm and the vss (actually, I would suggest testing all the wires that got wrapped around the driveshaft). Wouldn't surprise me if they need more fixing...