Well, this has been going on since day 1 when I bought this truck and it's getting aggrevating. My truck has this gremlin in it that kills the power to the lights and other items when I come to a stop. I'm sure it's going on all the time but it's most noticable during braking. My headlight flash like they were turned off and then on. The engine stalls and then refires. When logging with HPTuners the timing will drop to almost nothing and then back up to normal. While driving the timing will do the drop and recover, too.


Any ideas? I've checked and tightened all grounds and power wires.

 

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What a weird coincidence, I overheard someone at the dealership parts department talking about this same exact problem. Mine had a similar issue, but not quite as extreme. It would have voltage fluctuations like something was drawing a ton of power away from everything else, then the lights would dim for a second. It also happened most often during braking. I posted up about it years ago, never was able to figure it out.

Is the timing drop instant to zero, or does it gradually creep down to zero? How long does timing stay at zero and how long to return to normal? Have you logged ignition voltage? I would also log spark advance vs minimum final spark. Might as well post up the log you made

 

You need to scan the bcm and other modules with tech 2 to see if there are power related dtc's stored and go from there.

 

check your amp fuse the one next to the battery on the firewall... replace it... you will see corosion... if that doesnt help change the battery cable (positive).. its a common problem i fix it.. or just take it to the delaer theres a recall on that

 

I replaced the main fuse not very long ago. It was doing this before the fuse change and is still doing it. Do you know the recall notice number on the battery cable? I saw a notice similar to it that said to check the oring around the brake master cylinder going into the brake booster.

The timing advance falls to about 10 degrees for a split second and then goes back up. I'm not sure it's ever going into closed loop and staying there since the power seems to drop off and on constantly.

 

Loose or corroded battery cable is my vote too

 

hopefully its the cable itself. I've have swapped a few engines around in this truck over the time I've had it and the issue is still there every time after I do the install with the connectors retightened. I'll contact my GM service mechanic and see if he can find the recall notice on the battery cable.

 

For those that the lights are dimming slightly, you can try unplugging the power level sensor that shuts the alternator down when power draw is low... It's the sensor in the negative battery cable.

Mine seems to be fixed after unplugging that.

As for the OP... I doubt that'll help, unless your battery is toast when the alt cuts all power, the truck dies after the surface charge is gone...