Been lurking on here for a while soaking up all the info, but I haven't been able to diagnose this issue with my 2003 Z06:

Before you tell me to check and clean the grounds, I have cleaned the four grounds in the engine bay (not on engine) and per another post, ground 104 is for the front signal lights that are giving me the problems so that one was looked over EXTRA carefully. Here are the odd symptoms:

1. When running lights are turned on, left turn indicator in dash displays solid green and DIC and radio display lights turn off. If headlights are turned on interior lights remain off.
2. When running lights are turned on and left turn signal initiated, left turn signal will blink at double speed (no bulb out. Front and back are both blinking double speed)
3. When driving and brakes applied, DIC and radio display flicker to the rhythm of the idle.
4. When lock is pressed on key fob, car will lock and alarm will honk until car is unlocked.
5. If front running/turn signal light harness is unplugged (disconnected near passenger side headlight), alarm will not go off when locked with key fob.

If I wasnt already bald I would be pulling my hair out! Thank you in advance for your help diagnosing this issue!
The car does have the aftermarket Radio Flyer Bi-Xenon headlights, but I don't think that is the issue.
The

 

Update (bump). Cleaned ground in driver side footwell. Issue remains... Considering buying a new front turn signal/running light wiring harness as that piece when unplugged does allow for the car to lock without the alarm/horn going off so maybe the issue is in that harness?

 

There are things called SPLICE PACKS (SP-XXX) that all the ground wires terminate in. The one for the front lights is in side the front bumper facia. You will need to jack up the front of the car, remove the two access panels under the front facia and you will find it. Its a small square box (same size ground box as the ones on G-101 and G-102 behind the headlights but it doesn't have the ground tang on it.)

The SPs terminate all the front light ground wires and then use a heavier gage wire to bring that box to a chassis ground point.

Pop out the small access top for the SP and you will find a ground bar that connects ALL of the pins together. make sure that the ground bar and female pins are clean and fit tight on the ground bar male pins.

Bill

 

Thanks, Bill!

If that is the box with a different color top to it (off white instead of black like the box on the grounds), ive already located and cleaned that one. I used electrical contact cleaner, a wire brush, and dielectric grease when I put it all back together.

I am now troubleshooting the tail lights of the car. I found some grounds there that look corroded and working on those. Also considering the possibility of a Multi Function Switch. Maybe this is more than just one electrical issue.

 

Yes,, the multifunction switch AND the flasher unit can cause turn signal issues. Have you tried cycling the flasher switch a bunch of times to see if that changes things??

 

When the issue happens and the Radio, DIC and HVAC start acting up, find the fuses for the modules that are doing weird things and actually measure the fuse test points on top of the fuse for those modules to chassis ground. See what the voltage is reading.

You need to measure the (HOT in RUN & START) ignition switch supplied voltages to those modules to make sure it is at actual battery voltage potential and that they don't drop low or fluctuate under load.

The reason I recommend this is; Our IGNITION SWITCHES are a prime source of electrical issues. The electrical contacts inside the switch get dirty/burnt and can output lower than ideal voltages. That will cause MANY WEIRD ELECTRICAL ISSUES.!

 

LOL! Yep,, there is one in the rear also for the lights and rear stuff. It is behind the license plate frame in that access hole area.

 

I thought I was pretty technical but that is way over my head.... Would it be easier to get a new ignition switch and test it out that way?

 

Its your wallet.

If you own a C5, it would be to your advantage to get a good multimeter and learn to use it. Its easy to find the fuses that you need to test. They are in the passenger foot well fuse box. The fuse box cover has a legend in it that tells you what fuse is where.

It wont hurt to install a new switch but I would hate for it not to be an issue. Like I said, that ignition switch can be a real problem if its not functioning properly.

Bill

 

Sounds like I have some work to do

I'll report back.

 

Update. Grounds in back cleaned up. The brake light/interior light flicker seems to have been remedied.

However, the alarm still goes off when I lock the car with the key fob. To make it more interesting, if the **** that controls the dash lights is turned off, when I lock the car the alarm will not go off. When the **** for the dash lights is turned on, the alarm does go off...

The left turn indicator (on the dash) still stays lit when running lights are turned on.

I have a new MFS to install today and see if that helps anything.

UPDATE: New MFS did not remedy any of the issues.

 

Update: Problem resolved.

Cleaning the grounds helped with some of the issues, but the alarm would still go off when I locked it and left turn indicator light on dash would stay on when running lights were on.

Replaced the front running light wiring harness and all issues were resolved. Must have been a short in there somewhere.

Thanks to all and this community for helping me with it. Now on to the other issues...

 

SEE,, Persistence! That's all it took! Good work!

Bill