Wiring issue, maybe?

Tech discussions on the L77 6.0L V8.
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Blackjack
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Joined: Sun Dec 26, 2021 3:36 pm

Wiring issue, maybe?

Post by Blackjack »

Hey all. I'm getting misfire codes for cylinders 2 and 3. It seems to happen when I start it cold, as in 30-40 degrees in the morning. It goes away after 2 or 3 miles and comes back the next day. The first few times, I got a code for open injector circuit on both cylinders, since then, I just get straight misfire code for the same two cylinders.

Not sure if it's related, but It sometimes acts up when I shut it off. Intermittently, turning the key off just shuts everything down. The timer for the radio and accessories doesn't keep anything on. Sometimes it wont restart for a brief period, but other times it resets and let the radio timer start over by cycling the key. I'm kinda wondering if there's a bad relay, or maybe a bad ground somewhere.

It's 2015 and just hit 120k miles, btw. The oil change warning just popped back up, so that's getting done this weekend. Not sure if it's had a plug change as it had just over 100k when I bought it. I'm hoping it's wiring because of the open circuit codes I got the first few times. It has no modifications, as I live behind enemy lines and can't legally change my tune to accommodate AFM delete. Any help would be appreciated.
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elc32955
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Re: Wiring issue, maybe?

Post by elc32955 »

Just as an outlier, have you checked your wiring harnesses under the hood for any signs of chafing or disruption of the insulation? Going back many years, I had a start no run problem with an old 1981 Dodge Diplomat, refugee from the California Highway Patrol that drove me absolutely crazy. Sometimes it would act up, sometimes not. The only way the problem was located was by a detailed visual inspection and a very light misting of the harnesses with power on. A few small telltale sparks were the culprit, some insulation has just plain worn through and grounded on a wire connected to the ignition circuit that was up against the frame. Probably would have never found it otherwise.

Just thought I'd throw that one out there in case no one else chimes in, know it's low probability but... you never know!

Good luck!
Eric
System Manager and your tour guide for the day. 2015 Caprice w/LFX, former NC DPS staff car. Partial hybrid G8/SS/Camaro SS interior mods, SS MyLink radio upgrade, 2016 Camaro V6 rims, GMPP Malibu chrome exhaust tips, otherwise bone stock for now.
Sanford
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Location: Texas Gulf Coast

Re: Wiring issue, maybe?

Post by Sanford »

I would check the resistance of the two injectors before a cold start and compare them to the resistance of a known good injector. Could be a crappy spray pattern. Lot of possibilities on the problem. Should be able to do a lot of testing by swapping parts from other working cylinders.
Blackjack
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Joined: Sun Dec 26, 2021 3:36 pm

Re: Wiring issue, maybe?

Post by Blackjack »

Well, I got a p0202 code for open circuit on the number two injector. I monitored the misfire live data and sure enough, number 2 had 17k misfires. I swapped the injector with the number 4 cylinder and monitored it again. Misfires all moved to number 4. I need an injector. It seems to be P/N 12639221. No parts houses have them and Amazon won't ship me one. I have to drive to work on Tuesday and it's 60 miles round trip. I would rather not make a whole trip with the I'm hoping the dealer will have one, but I can't know until tomorrow. At least I know exactly what I need.
Sanford
Posts: 356
Joined: Mon Dec 12, 2016 9:38 pm
Location: Texas Gulf Coast

Re: Wiring issue, maybe?

Post by Sanford »

Do you have a way to check DC amperage? It would be interesting to jumper the injector with 12 volts and see if it clicks and how many amps it pull. You can’t leave the voltage applied for very long or you will overheat the injector.
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elc32955
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Re: Wiring issue, maybe?

Post by elc32955 »

Still sounds to me like you have two problems working, and the injector will solve one but not the other.... I'd say an intermittent no-start bears looking into right quick like! :( :(

OH, btw you might want to read the Smog thread in this section. Apparently other residents have modded their tunes for AFM delete, went through inspection, and passed! There is hope!

Eric
System Manager and your tour guide for the day. 2015 Caprice w/LFX, former NC DPS staff car. Partial hybrid G8/SS/Camaro SS interior mods, SS MyLink radio upgrade, 2016 Camaro V6 rims, GMPP Malibu chrome exhaust tips, otherwise bone stock for now.
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