Strangest issue... need advice
 

So a couple weeks ago at the track I kept getting code P0628 and P12A6, both referencing low voltage to fuel pump A. I’ve since thrown a BCM code that causes Stabilitrak to light up all ABS and Traction lights that also references a low voltage to BCM code.

Here is the kicker.... I can recreate this issue on hard left turns, at any speed. Straight line pulls and right hand turns cause no issue. My builder and I have been going through the car from front to rear checking for pinched wires, loose grounds etc. he is thinking that the Fuel Pump power control module might have a short in it causing our issues.

Since i am having my differential rebuilt and the FPCM is above the diff we will swap it out due to easy access. Can anyone think of anything else to check? I have literally been under the car for 2 weeks and can’t find any wiring that is out of the oridinary. I’ve even had the car running while making my way through the harness shaking things but can ONLY get the DTC when rolling and making hard left turns at any speed and any throttle position.

Yes I’ve already checked the harnesses near the front wheels, nothing binding.

Can you acess the BCM also and see if has pinched wires?

I believe the BCM is in the trunk and we have inspected all harnesses and grounds leading to the trunk, as well as all modules and battery in the trunk as well. So frustrating

Check the wiring harrness in the left rear wheel well, behind the liner?

Yes. Traced that one all the way to the tank.

With all due respect: In order to verify the ground connections, the bolt head (a), the connector on the wire (b) and the body around the connection (c) have to have the resistance checked between them.

a to b, a to c and b to c. It also helps to have the unit running so that it's under load. You can probably get away with the b to c test only. The resistance readings should all be very similar, like 1 ohm or less depending on the meter.

It's a PIA, but you also have to expose bare metal on each piece, not a fun project.

Good luck,
Nick

There was a technical bulletin for the wiring harness to the power steering motor. I think it was a grounding issue or a loose connection of some sort if my memory serves.

While it sounds a little far fetched, it could be that you're losing power to the steering module causing the stability control to question where the steering is or something along those lines.

Since your '18 is no doubt still under warranty, and there appears to be a TSB that is at least remotely relevant (post #7) why not let GM troubleshoot and fix it?

Sounds like his car is modified. Most likely why he hasn't taken it to the dealer.

I had an issue like this and it was fixed (so far) by the more recent TSB (wiring harness short)

Can you link me to the TSB?

Here is a screen shot of the invoice.

subscribed.

I'd love to hear how this goes. I had a similar issue on my Z06... I ended up selling the car.

Which issue did you have on the Z06? The Stabilitrak or the fuel pump voltage?

I would definitely check out the wiring near the passenger headlight. There is a service campaign to add extra protection to it, as it can rub on a sharp edge and cause all kinds of issues. The harness on my 18 had a heavy gouge in it, and I have no doubt it would have worn through given more time. I could definitely see this being an issue aggravated by turning.

There’s actually 3 different wiring related bulletins for these cars. I’ll try to find them.