2018 Silverado 1500 e-assist system - How does it work?

e9coupe · July 10

We just got in an '18 Silverado from an insurance auction with the e-assist hybrid system and it's not charging the 12v battery. I've search and found others that had a similar issue but no one ever posted that they solved the problem. It was hit in the right front near the 12v battery and inverter but it was minor and didn't get into the area enough to damage any wires, etc. It starts with a jump and runs and drives but since the 12v battery isn't charging it eventually dies.

Does anyone know how the e-assist system works as far as the alternator/motor, charging the HV battery and charging the 12v battery? There's no wires going from the alternator/motor (whatever you call that thing) directly to the 12v battery. It looks like there's three orange wires going back to the HV battery and that's it, so the 12v battery would have to be getting charged from the HV battery?

Also, the only codes we got were low voltage related and I went through an reset any crash related processes I could find.

Edited July 10 by e9coupe

rlcole321 · July 10

there has to be some sort of connection to the 12v battery,

this might help some

GM 5.3 Liter V8 L8B EcoTec3 Engine With eAssist Mild Hybrid System | GM Authority

seems braking is what charges the 12v battery, conldn't find any schematics

e9coupe · July 11

Thanks for the link. That's the kind of info I've found but nothing with any detail of how it all works together.

The 12v battery has one ground wire and the positive post has a terminal block with three large wires (fused). Fuses are good. One goes to the starter, one goes forward to power steering rack (I believe) and one goes to the inverter. So the inverter and 12v battery are connected. The BAS has three large wires coming out of it all covered in orange sheathing. I don't see any other wires connected to the BAS but I could be wrong.

If the wires are what is stated above, the generating function of the BAS would send current to the HV battery/inverter, which would then send current to the 12v battery.

I've reset everything I could find in the scanner as far as HV goes with no change. The voltage gauge on the dash also works and shows low voltage (around 10.5v and continues to go down).

I've run out of logic and the rest is over my head.

newdude · July 11

4 hours ago, e9coupe said:

We just got in an '18 Silverado from an insurance auction with the e-assist hybrid system and it's not charging the 12v battery. I've search and found others that had a similar issue but no one ever posted that they solved the problem. It was hit in the right front near the 12v battery and inverter but it was minor and didn't get into the area enough to damage any wires, etc. It starts with a jump and runs and drives but since the 12v battery isn't charging it eventually dies.

Does anyone know how the e-assist system works as far as the alternator/motor, charging the HV battery and charging the 12v battery? There's no wires going from the alternator/motor (whatever you call that thing) directly to the 12v battery. It looks like there's three orange wires going back to the HV battery and that's it, so the 12v battery would have to be getting charged from the HV battery?

Also, the only codes we got were low voltage related and I went through an reset any crash related processes I could find.

What codes do you have? The actual codes not just "the only codes we got were low voltage related". Which if they are low voltage system codes they are relevant since you are having an issue with the 12V battery.

Are you getting any "service charging system" messages or battery lights?

Starter/Generator Control Module handles lots of operation including 12V charging operations.

Edited July 11 by newdude

e9coupe · July 11

13 hours ago, newdude said:

What codes do you have? The actual codes not just "the only codes we got were low voltage related". Which if they are low voltage system codes they are relevant since you are having an issue with the 12V battery.

Are you getting any "service charging system" messages or battery lights?

Starter/Generator Control Module handles lots of operation including 12V charging operations.

I'll get the list of codes. Battery light is on on the dash and "Service charging system" displays. There's a couple messages that pop up. Battery and charging related. And the voltage gauge is showing low voltage so that makes sense. When I generalized the "all low voltage related" I meant that low voltage can cause a lot of codes based on one thing being wrong and they all referred to low voltage. Didn't see any HV battery, inverter, codes, etc. We get a lot of vehicles in with low voltage issues because they sit so long. We always start there.

My assumptions... It's an insurance vehicle and was being driven when it was in the accident so I'm assuming this charging problem is a result of the accident. When we received the vehicle it still had enough power in the 12v battery to start it and drive around but eventually died. Confirming the problem started with the accident.

If it were a software kill feature for a crash it would cut off power/ignition or the starter or fuel, but a non-charging issue has to be something that was damaged or a strange by-product of something else going bad. An inverter reset or something beyond me.

BTW, the scanner showed the HV battery is at 47% so I don't think that's an issue.

e9coupe · July 16

Finally got around to checking the codes again. It was 113deg here for days last week and I didn't feel like sitting in the truck in the sun. 8-)

They cleared the codes at some point and they haven't come back. I ran the truck for a few minutes and still nothing so they decided to sell the truck as-is. We buy and sell insurance salvage vehicles and sometimes just decide to move on without spending to much time on them. I'm still really curious and will be checking around to see if anyone figures it out. Everything is good except for charging the 12v battery.