Will not start after changing computer

1998 GMC JIMMY
177,000 MILES • 0.6L • V6 • 4WD • AUTOMATIC
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HERRERATINO8687
  • MEMBER
  • 1 POST
A friend was giving me a jump and connected the jumper cables wrong and fried my computer. The gas gauge was reading below zero and the truck had no power at all. I replaced the computer with a used one from the junkyard. I have power now but the car won't turn over. I reached the ignition switch and bought a new battery and it still won't start. I tried resetting the computer with some instructions I got off YouTube and that did not work either. Please help
Jun 29, 2021 at 1:18 AM
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ASEMASTER6371
  • ✓Experienced Mechanic
  • 52,796 POSTS
Good morning,

Can you communicate with the replacement ECM? Does the check engine light work?

When you crank the engine, you should see the tach move up a little indicating the crank sensor is working.

There may be more damage from the cables being hooked up backward.

Check all the fuses with a test light and verify power on both sides of the fuse.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Roy
Jun 29, 2021 at 8:26 PM
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