Today, I was assigned a 2015 Colorado 2.5 auto that just came from PDI. It had a complaint of MIL on and stalling. Only 9 miles were on the odometer. Taking a fast scan with GDS, I saw this...

Codes Scanned

What's in common with these codes? The 47UA fuse in the UBEC powers up all these components. Checking the fuse, it was blown. I replaced the fuse with a Fuse Buddy and turned the key on. The fuse did not blow and the current draw was 1.9 amps. The codes all cleared and did not reset immediately. I started the truck and the fuse blew after 5 seconds running. Putting another fuse in the Fuse Buddy, with KOEO, it did not blow and the draw was 1.9 amps again.

I replaced the fuse with a tail light bulb wired to two correct sized terminals. With KOEO, the bulb did not illuminate. Starting the truck, after 2 seconds, the bulb lit dimly then slowly brightened until after 5 or 6 seconds, it lit brightly. I revved the engine a few times and shifted from drive to reverse several times and was able to change the brightness of the bulb and make it go on or off at times.

Sounds like a harness ground out, doesn't it? With the bulb fully lit and the engine idling, I carefully moved and shook the engine wiring harness. At the left front corner, near the O2 break out, I was able to turn the light on and off with minor movements. Looking closely, a harness standoff had not been installed at the factory and the engine harness was sitting on top of the rotating power steering pulley and the end rib in the pulley had cut through the harness. Cutting open the harness and repairing the power feed wire from the F47UA fuse repaired the problem.

James from Florida

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