Josh Dockstader

Looking for some help as my car is really getting the best of me. The car is a 2006 Z06 and is regualrly raced. At autox one day the car harshly corrected and the "Service Charging System" indicator came on. After inspection the horn fuse was blown. I replaced the fuse and drove the car. I had no problems unless I got hard on the throttle and then the fuse would pop again. This didnt seem to be a big deal until I autoxed again and the car started to missfire and give codes of P0355 and P0341. I was also getting a voltage drop down to 11-12volts.

I replaced the alternator with no change. Driving home 3 hours from the track the voltage slowly rised to 13.5v from 11 when i finally got home. The voltage would fluctuate .5v the whole time driving

Then removed the horn and horn relay. This then stopped the horn fuse from blowing but I still get the same codes, missfire and voltage drop on my second runs at autox or second lapping session on the road course.

I have checked the wires from the alternator to the fuse box to be good. Does anyone have any insite on what this issue might be caused by?

Thank you,
Josh

MTPZ06

If alternator and battery are good, it sounds like a bad ground somewhere.

Josh Dockstader

Main battery ground behind the b-pillar is good. Two grounds below the fuse box, two on the block by the starter and two at the front of the car both left and right side are good. Maybe I am missing one?

nuke61

Have your alternator and battery load tested to make sure they're good. Does this only happen when auto-Xing? Can you do a full throttle straight run, or does it misfire then too?

Josh Dockstader

I have taken the alternator and battery to oreillys to bench test them. Both are good. I even replaced them just to be sure. It happens both on road course and autox. It happens on the second typically. I forgot to mention the car has also thrown a P0621 Generator L-Terminal Circuit code. I am thinking it could be a bad ECM maybe?

RamAir972003

Try swapping computer ecm might just have gone bad.

spartan8270

What spark plugs are you running? This may sound funny but and issue with spark plugs can cause obviously a misfire code but also a charging problem. Try swapping out plugs

Josh Dockstader

NGK TR6 plugs. I ran them last year with no problems. Could it still be the plugs causing the issue?

spartan8270

Yes this has happened from my experience. Has to do with grounding and interference. I would go grab a set of new TR6's and replace them first. They are so cheap and easy that's where I would start. Also do not apply anti seize to the threads

Cha_Cha

What type of voltage drop are you getting between the Battery Positive Post and Alternator Output with car at full temperature with all accessories running (AC High, Rear Defroster ON, Seat Heaters ON)?

If its more than .1V you will have charging issues since you are essentially straining the alternator.

As far as the Service Charging Warning - P0621 Generator L-Terminal Circuit code, You can easily disable the message with HPtuners and run whatever plugs you want.

Josh Dockstader

I replaced the plugs a few weeks ago. They had anti seize on them and I had put some on again. Still had the same issue. Street driving the car everything is fine. One I start racing I get the missfire and voltage drop

Josh Dockstader

Forgot to answer your second question. I can go wot on the street in a straight line and have no issue. However sustained racing seems to cause the missfire and charging draw

Josh Dockstader

On the way home sunday i was seeing a fluctuation on the volt gauge of .5v both at idle and driving on the interstate. When got home I checked power from the alternator to battery and it was a .1v drop to the battery.

Josh Dockstader

New PCM did not solve the issue.

Tested voltage again with the car warmed up and everything running. Was getting 14v at the alternator and 13.5 at the fuse box and battery. I let the car sit and tested voltage with the engine off and got 12.5 at the battery, fuse box and alternator. Ohmed the power wire and it was good.

Possible that the starter would cause this voltage drop?

MTPZ06

Damn, all that for nothing.

Josh Dockstader

Yup

nuke61

Would you agree that it seems to be heat related, since it only happens after the 1st lap of track time? Do you have a datalogger, HPTuners or the like, so see if it's timed to, say, when the radiator fans turn on/off?

Josh Dockstader

Yes I do. Heat very much seems to be a factor. Perfect example is that after autox last weekend the car was charging only 11v. After a 3 hour drive home it slowly charged up to 13.5v.

I do not have a datalogger at the moment. I belive this would be a very good investment however now.

colanut

JUST CHANGE THE BATTERY CABLES AND BE DONE WITH IT.
Cut the insulation off the old ones when your done.
Don't forget the ground straps also.

Unreal

Plugs show a warning, but don't actually cause issue or dropping of voltage, just a dash warning from the emi.