2018 Electrical Problems

Capt Bob · March 17, 2021

Well the ol' 5.3L has been a very reliable ride since new and I had hoped it was one that dodged the at least some of the problems that are mentioned here but not quite.

Truck running fine for 26,900 miles. I had recently completed a pan drop (and replaced with a drain plug installed) and filter replacement. While I was under, I pulled the thermostat and "flipped the pill". Running cooler and no leaks. I also replaced the engine thermostat with a Katech 174 degree model. Engine running measurably cooler though not cold by any means.

That stated, yesterday I was loading trash in the bed and when I started the engine, the world went nuts. The gauges were cycling off and on, multiple warning displays on the DIC, chimes ringing, CEL lit and when I engaged the transmission, it entered limp mode. I drove a short distance and shut it down. Waited a couple of minutes and re-started. Same as above. Repeated the drive procedure only slightly farther and shut down. Lifted the hood, checked fuses, wiggled the battery ground cable and harness on the ECM. This time it started and everything ran normal but CEL was still lit. Drove it about 10 miles to the job site, took code readings and shut it down. Codes showed U0073 and U0101. Lost of communication, which makes sense. When I started it back up, back to abnormal. Repeated the drive procedure/shut down/wait until it returned to normal and took it home.

This morning, it started and performed normal except for the illuminated CEL so I dropped it off at the closest GM Dealer. I'm not expecting much but it's still under warranty and I didn't feel like chasing gremlins and throwing money at them. I believe I read something here similar to my experience but a search really didn't come up with the exact symptoms. Any thoughts are appreciated.

Gagliano7 · March 18, 2021

Probably a loose or bad ground.

Capt Bob · March 18, 2021

Going to pick it up now. They replaced the negative battery cable and associated ground wire (s). I read in another thread that the cable had been suspect in the past due to high resistance issues that develop with age. Hopefully that solves my issue. The truck has been very good prior to this. Compared to some on this Forum, mine is mostly problem free.

Must have been built on a Wednesday.

rav3 · March 18, 2021

1 hour ago, Capt Bob said:

Going to pick it up now. They replaced the negative battery cable and associated ground wire (s). I read in another thread that the cable had been suspect in the past due to high resistance issues that develop with age. Hopefully that solves my issue. The truck has been very good prior to this. Compared to some on this Forum, mine is mostly problem free.

Must have been built on a Wednesday.

Thanks for the follow up on this. I was going to suggest like Capt Bob did but didn't because you had an '18 model & combined with low miles, thought maybe it wouldn't or couldn't be ground issue BUT Guess I was wrong. You might want to consider adding add'l grounds like this video. I am planning on doing it on my '17 when the weather warms up.

2014-2018 Silverado/ Sierra Ground Upgrade K2XX (Prevent Electrical Issues)

Capt Bob · March 19, 2021

Well I picked up the truck today and they did indeed replace the negative battery cable with associated ground wire. Seems to run fine at this point.

There is a "bullentin" (their spelling, not mine) #18-NA-161. It appears they test for a voltage drop in the cables and found the negative cable with a higher than spec reading.

Hopefully this will last a couple/three years before it goes nuts again.

Rav, I've seen this vid some time ago. It will be my next maintenance project. Thanks for posting.