BlindSpot

The electrical system in a C6 is "sensitive" (but not much different than a lot of other cars I've come across), and a drop in voltage (11.8v is a threshold), or a possible loose or bad ground connection can cause unwanted strange gremlins to appear.

So, this weekend I had a little time, put the car on the lift and I thought I would chase down all of the ground lugs and the starter positive terminal which is notorious for loosening. In my 09 Z51, I only have 11 of the 12 identified ground lugs. G402 located on the passenger's side rear axle is not there. The 6mm ground lug is, but apparently the harness was redesigned somewhere along the way and there is only a grounding provision of the left rear axle side G401.

So, of the 11 grounds and positive starter lead I found:

The starter lead was loose and took about 2/3rds of a turn to complete tightness.

Two of the 11 ground lugs were loose and needed tightening:

G101 was loose, Engine compartment front left, (driver's side) 6mm lug located on the frame member.

G401 was loose, rear axle, left side, 6mm lug located on the frame member.

Was worth the time put in. Glad I used the idle time to get to it.

BTW, if you check yours, DO NOT ATTEMPT to check the positive starter lug, or the engine ground G106 (engine ground right bank), without first disconnecting the battery. There is no way you will not short the wrench out on the starter lug, or hit the starter lug checking G106.

Ajaste

Valuable data point. Note that schematics showing locations of grounds can be found at

https://www.corvetteforum.com/forums...locations.html

BlindSpot

Yes, thank you! I thought they were out there somewhere, but unable to find them.

Ajaste

Sure!

jimmie jam

I'm wondering...saw a post a while back regarding the A6 "locked" in park. It addressed the problem of a incomplete ground that stopped the shifter solenoid from functioning. Maybe I should be checking these ground connections...

BlindSpot

A poor ground increases resistance which reduces voltage in a circuit. OHMS Law V=IR. So, it's possible that if a ground circuit to the solenoid is deteriorated enough, the voltage drop to the solenoid could be reduced enough to be unable to energize the solenoid. I don't have an A6 so I cannot comment specifically in the shifter problem.

RICH 28

I doubt it is a grounding issue because the dealer would just put in a new shifter assembly which includes the solenoid. I doubt they will do anything with the ground locations.

jimmie jam

You are missing the point here. #1, I'm not taking my car to the dealer (and would not). #2, there have been threads where the dealer has replaced the shifter assembly and the issue started again in short order. #3, a member has added a dedicated ground wire to the solenoid and said that has stopped the issue. FWIW.

BlindSpot

One thing you can do is a voltage drop test. Again, I don't know what you're up against to access the circuitry to/from the solenoid. I have no experience on the C6 with an A6. I have had failed solenoid shift lockout problems on European cars (they all use similar devices). Part of the circuit includes a brake switch as this this the switch that energizes the sol in typical designs. Two vital points are the sol connector and the switch (brake).

The voltage drop test you can do yourself if you have a VM, the time and can access the circuit. Google voltage drop test. There are right/wrong ways.

Not So Fast

YOU HAVE A LIFT ??? Damn you man, I would kill for one, well not really but you know what I mean.
NSF

BlindSpot

I've had the lift for about 5 years now. I bought it when I was building my FF Cobra. It was invaluable for that build and the best garage investment. I had mine delivered to my driveway, then installed it myself using my engine hoist.