cvccbum

Very odd problem I've come across and I'm hoping some guru is here to help! I was driving down the road and was coming to a stop and the car stalled. (05 M6 LS2) When I clicked the start button again, all the lights inside were on, but no starter noise. Tried a few more times, nothing. Car was spewing out random stuff like my gas level went to 0 then back up, and other odd things. It did the gas thing a few times and then finally just said 0.

After that I tried to start it again, and it tried to start then stopped as it normally would if it wasn't going to start. (Starter did a full 10 seconds). After that, I turned it fully off and tried again. Now the lights don't even come on. The radio blinks for a second then turns back off. Accessory mode works perfect. That's what throws me off... I tried to load a tune and no communication between the diag port and PCM. I checked all fuses and they look fine.

Anyone ever ran into something as bizarre as this?

EDIT: The most recent thing I have chained is I had to directly hard wire the fan instead of using its connector because it fried the connector. I had the fan running at 95% and didn't know of the issue they seem to have at that level. I did this awhile back tho, car has been fine.

Marc V.

Bad battery.

cvccbum

I've checked the battery, and its fairly new. When I press the ignition button (the lit up green part), it does nothing. Accessory works perfectly though. I've had a dead battery in this car many times (which is why I replaced it awhile back) and it's totally different. The time the car tried to crank, the starter was at full speed (and voltage was still 13+).

speedlink

Sounds like a dead or bad battery. Make sure all connections are tight and ground and starter wires are tight and not corroded. And of course, have the new battery checked. Could be just la bad cell. Still this would be a bad battery and need to be replaced. Yes, this could still happen with a new battery.

Let us know how it turns out, so we all have new information. It can help the next guy.

TKgs2010

I'm thinking battery myself. I recently had my GMC P/U do a similar thing (not exact, but very similar), and after testing, I found the battery was down a cell. The truck only had 3,000 miles on it, so it CAN happen to a new vehicle. After replacing the battery, no more issues, problem solved. Keep us posted, and good luck.

StKnoWhere

cvccbum

New symptom: When you press the green button to start car (without clutch or with clutch pressed) the car still goes dark. After 15-20 seconds, it lights the dash up like normal. Still does not start though.

Battery reads 12.8 volts even after doing all this testing with no charger. Like I said before, the car turned the starter that one time (randomly) and did not hiccup (for the 10+ seconds it did it). Also a dead battery wouldn't account for the odd messages it was showing.

Also, I have all my gauges and external oil pump (for the turbos) wired to the fuse box and when I hit the green button to start (even when the dash lights are out for those 20 seconds) they come on. Also, you can tell when the battery is going because the oil pump also goes slower due to less voltage. I've tried other batterys/jumping so I'm 99% certain its not that

I built this car this winter with a custom twin SC61's (made it similar to the UPP'S turbo kit) in the fenders so my PCM has been enclosed above a turbo. This is alot of heat and I'm thinking the PCM might have gotten too toasty? Thanks for all the input though guys, hopefully someone has the magic idea!

cthusker

If you were in the middle of tune and lost power (car or lap top) you can do a real bad number on your ECM! It can corrupt all the data and you will get all sorts of strange things happening.... Most time if you can't reflash it's new ECM time... Hope that's not the case...

foremaw

For 'Vettes, always eliminate the battery first. I recommend a full charge/load test. If the battery is indeed good, move on from there.

coolcat

Just another reason why I traded my 05 coupe in on an 08 coupe.
My 05 did similar random odd things and the dealer could never figure out how to fix the problems.

Never again will I purchase a new generation Corvette in its first model year of production.

MARSC6

I was going to suggest a bad ground but having the PCM sitting over a turbo sounds like trouble.

cvccbum

I turned the headlights completely off (always leave them on) and it says 'Headlamps suggested'.. it's 100% sunny outside. Anyone know what controls that? Maybe that could lead me in the right direction to whats shorting out/ground messed up haha.

cclive

This makes complete sense...the car goes dark because the relay that engages the starter is kicked in when you push the button. Then it stays that way until the system stops what it thinks is the engine cranking. This is when everything comes back. This is certainly indicative of a low battery or a bad battery connection...a battery that can't push against a big load, but still can light the lights etc. Secondly, the biggest enemy of electronics is heat.

eboggs_jkvl

Battery or connection is corroded, loose wire.


Elmer

chris12.8

batteries can have volts without amps, may be the battery.

eboggs_jkvl

Another thought... Bad battery caused by a lack of a recharge circuit. If the alternator isn't charging, the battery will take a dump. So, you need to check your charging system and THEN probably replace your bad battery.

Elmer

cvccbum

It does the no lights thing even when the clutch isn't engaged (shouldn't try to crank, right?). When the car stalled the first time, I tried to clutch start and it wouldn't. After it did the whole random DIC warnings (almost like I was tuning), the starter DID go but wouldn't start. As I said before.. there was 0 slowness in the starter (the one time it tried), the car just wouldn't start. I've hooked up a new battery, and even directly put a jump starter on the starter and a new ground, etc. It's still saying weird stuff with the DIC too.

It sounds like a short to me, but I don't feel any burnt wires under my pcm (hard to see with a turbo there). Can wires melt inside the wire looms but the looms not melt?

JPN7075U

I'm thinking battery and I manufacture batteries.

HOXXOH

I've heard of other '05 M6 cars with similar problems that trace to heat issues. When they cool completely the problems went away too. Just parked in a sunny spot on a hot day caused a problem for one guy. Do a search here and in the tech forum.

Another thing to check is the positive cable cleanliness (corrosion free) and tightness of the connection. If it's not clean the load to start can be too much to handle.

And yes, wires can short inside with little evidence on the outside.

cvccbum

Wires to the battery are brand new. I've tried multiple batteries, jump starting, battery chargers, a jump charger, etc. All on new grounds, new wires, everything. I've tried using other locations for ground etc too.

I also know the DIC yells at you if voltage gets too low while driving, it yells 'Service Charging System' over and over. It never did this, and as the battery volts read normal, I don't see the car stalling from a bad battery (the alternator works)... I have had tons of bad batteries in my life and I know something else is going on here..

anyone had a bad PCM before on these cars and seen what it does?