No start, Low voltage message

[choproxy]

2002 convertible with 17K miles. I have had the car for 2 years with zero problems, untill yesterday. The car turns over fine but will not start or even fire. The battery is good (replaced it) and the car cranks and the lights and horn all work fine. But there is a voltage delivery problem to some parts of the car (poor ground or 12V?). The car voltage gauge and DIC diplay 5.8 Volts and I get warning Low voltage, plus a punch of lost communcaition codes. Some of the time the DIC is flashing, resetting and dinging, but the driving lights radio etc are all getting full power. When this is happenning the starter relay just clicks when trying to start.

Most of the time the battery voltage on the guage looks good with Key on. Flicks high and drops to 13.5v, but drops over the next second to the lowest end of the scale (8V). A volt meter show 13V and any fuse that I probe also shows 13v.

The car will start some of the time if I immediatly crank before the volatge drops. and once it is running and I clear any codes the car runs fine untill I shut it down. When running the battery voltage show 13.8V, I think the alternator and charging circuit are good

Im sure this is a bad connection problem for 12V or ground to PCM, or other computer/control related electronics. I have checked the obvious battery conenctions to the fuse box and ground.

Does anyone have expereince with this kind of problem and a direction on what to check next?

 

[c4c5specialist]

HI there,
i would recommend checking both battery terminals, as they should be torqued to 11 ft lbs.
Then, check your starter connections and the negative ground cable, above the starter and below the exhaust manifold on the passenger side.
This is what I would check first.
Allthebest, c4c5

 

[vette-dude]

Might also re-check that battery is really okay. Some new ones are defective.

Randy

 

[choproxy]

Yes I was hoping that was the probelm too. But I have a 2nd 2002 Vette (Got to have one for the Wife too). So I swapped batteries (hers is just 5 months old). Same results.

I was able to start the car intially after a few trys. But now the voltage guage kicks high (normal) with key on and then drops to the lowest reading and repots low voltage. But the batterry show 12.8V with an meter and the lights, horn, wiper, radio, locks all work like normal. The car intially would crank but not fire. Now the starter clicks in and out and no crank. So the porr connection is worse?

So far I have checked the easy stuff. Battery, fuse box connections and ground on the frame.
Next was to remove and replace connectors by the fuse box and the computer in the passenger footwell and check the starter and ground connections

Any other suggestions?

 

[vette-dude]

Then as C4c5 Specialist said, it must be in the connections. The only other thing I can think of is a possible dead short in the ALT. Maybe you could try unplugging the Alt and see if it has any effect on the situation. Don't know if this will work and if it would cause any damage so maybe someone else can chime in with more accurate advise.

Randy

 

[LLC5]

Make sure the posititve and negative battery terminals are clean and tight. No corossion at the cables or down the cables. Any corossion is bad. The terminals need to be tight on the battery. Check the ground cable to the engine and the body of the vehicle. Check the connector at the fuse panel from the positive cable. Any corossion on the battery tray under the battery? Below that is alot of electronics and wiring that could be damaged.