ZL1 Issues

[Fraxum]

My low mileage 2015 M6 Zl1 has 2 issues the dealer is having problems figuring out.

One is the Service Stabitrac Service lights keep going on when I go around a corner, a chime goes off and a warning on the DIC says service power steering. The light also sometimes goes on when going straight. But turn the car off and restart and all clear, no codes.

The other is a fairly loud rattle I think coming from the passenger side of the car, but mainly when cold. The sound changes fades out and comes back when shifting and just about completely goes away when warm. Thinking perhaps NPP here, but I did not see the NPP rattle in old threads describing it only when cold.

I do have another NPP exhaust I could throw on there if I had to.

[vicnkathy]

The computer could be bad. The rattle could be anything. Have to get it on a lift and see. Maybe the sensors near the shocks are loose, causing both issues?

[Fraxum]

Originally Posted by vicnkathy

The computer could be bad. The rattle could be anything. Have to get it on a lift and see. Maybe the sensors near the shocks are loose, causing both issues?

I did not know the shocks have sensors. Thanks!

Makes sense, but no rattle when the car warms up. Hmmm.

[Redlineviper]

Sounds like either a bad computer or the harness plug may have a bad connection. This is not an uncommon issue. The rattle is likely exhaust related since it is temperature dependent.

[Sakudog]

Just an FYI to everyone, the Electric Power Steering system is VERY sensitive to grounding issues. Case in point I was getting a warning light "service power steering" 1 out of 5 times I'd start my car last couple of weeks and got progressively worse until it just wouldn't work.

I finally got around to checking my battery cables and the ground was very loose. After tightening the ground cables the EPS has worked very reliably.

So a bad ground anywhere could be causing the issue, I'd ask the dealer (or if you're like me and don't trust them) yourself to review and check every ground the car has, starting with the easy one at the battery terminal.

[KaBoom1701]

Was trying to speed read your build thread...

Seems you've changed most your suspension to BMR goodies. I'd be willing to bet there is a lose MRC sensor wire or like Sakudog said a bad ground somewhere causing ECU issues.

IF you have a Dashlogic controller you can set the NPP to open and see if that clears up your raddle? Or fuse full would work. Try to eliminate the NPP flaps as the issue.

[Fraxum]

Originally Posted by KaBoom1701

Was trying to speed read your build thread...

Seems you've changed most your suspension to BMR goodies. I'd be willing to bet there is a lose MRC sensor wire or like Sakudog said a bad ground somewhere causing ECU issues.

IF you have a Dashlogic controller you can set the NPP to open and see if that clears up your raddle? Or fuse full would work. Try to eliminate the NPP flaps as the issue.

Those were my old threads. This is my third 5th gen. I bought the ZL1 because it is great out of the box.

My current mods:

• Exhaust commander
• Catch can
• GTO clutch reservoir
• Amp upgrade

I can control NPP from the garage door opener. No difference in the rattle either way.


I do pull the battery ground when I mess with stuff, I am pretty sure its nice and tight. Will recheck if they give up.

[KaBoom1701]

Oh crap....then forget everything I said. Lol

[Fraxum]

Originally Posted by KaBoom1701

Oh crap....then forget everything I said. Lol

No worries. Update, GM thinks the Stabillitrac problem is a Yaw sensor. Makes sense I guess. They don't "Hear" the cold rattle. Really I'm not that picky, it's hard to miss. I guess I will have to switch out my NPP set up for LTs to see if its the exhaust. Bummer. On their target fixed date they will have had the car 8 days.

Not a good start for my ZL1. But it looks like such a bad boy. It will be hard to part with it. I have seen the new CA6 Camaro at my dealer. I like it but not feeling it so much.

[Fraxum]

Originally Posted by KaBoom1701

Oh crap....then forget everything I said. Lol

Hey, you have the no-tune power mods I plan do this spring. How do you like that setup? Was there a before and after dyno?

(Can I hijack my own thread?)

[Sakudog]

Originally Posted by Fraxum

No worries. Update, GM thinks the Stabillitrac problem is a Yaw sensor. Makes sense I guess. They don't "Hear" the cold rattle. Really I'm not that picky, it's hard to miss. I guess I will have to switch out my NPP set up for LTs to see if its the exhaust. Bummer. On their target fixed date they will have had the car 8 days.

Not a good start for my ZL1. But it looks like such a bad boy. It will be hard to part with it. I have seen the new CA6 Camaro at my dealer. I like it but not feeling it so much.

Longtubes would replace the manifolds/cats, the NPP is the catback part of the system. Also, the NPP system can support some serious power...

[Fraxum]

Originally Posted by Sakudog

Longtubes would replace the manifolds/cats, the NPP is the catback part of the system. Also, the NPP system can support some serious power...

Yes, my second NPP setup has a Magnaflow xpipe to tone down the LT rasp. I also have a full 3" Magnaflow setup I can also use with LTs. I have LTs too. I will coat them before putting them on the ZL1.

Of those two other exhaust systems only the 2.5 inch NPP setup will fit on my current stock ZL1. That would make it really quiet. It could be interesting since I would lose no power.

I also have an AGP twin turbo setup that fits the 3" exhaust, but I have a buyer for that. I decided against going with a twin FI setup. But wouldn't that be cool. Easy 750 hp.

[Chrispy]

Do you have a CAI on the car and relocated your ground? If so that ground relocation (or loose stock ground) can cause the issue with the power steering

[Fraxum]

Originally Posted by Chrispy

Do you have a CAI on the car and relocated your ground? If so that ground relocation (or loose stock ground) can cause the issue with the power steering

No CAI yet. And I do not plan to relocate the ground. The battery ground is tight. The dealer says GM wants to replace the Yaw sensor. Hope fully that does it. Looking forward to driving my ZL1 again. Even with the rattle.