No spark on three cylinders driver's side?

126,000 MILES • 5.3L • 4WD • AUTOMATIC
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CHUCK8
  • MEMBER
  • 1 POST
I changed the coil packs and injectors and did not fix it. Changed computer ECM now it doesn't start at all security light on.
Oct 23, 2024 at 6:30 PM
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STRAILER
  • ✓Experienced Mechanic
  • 55,554 POSTS
Yep, it sounds like the coil drivers inside the PCM have gone bad, can I ask if you had the PCM pre-programmed? If not, this will be the problem. The PCM must be programmed to the truck to work correctly, you can get a preprogrammed unit by searching Google or Ebay.

Here is how to replace the PCM correctly. Check out the images (below). Please let us know what happens. You may have a crankshaft sensor that is weak and produces an erratic signal to the PCM FYI.
Oct 24, 2024 at 3:36 AM
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