You can disconnect the BATT terminal from the Alternator and insert the amp meter between the wire and alternator.. It should read zero amps if the alternator is good.

The other thing that could be bad is the head light control module. It should not be drawing any current once the head light is up or down.

 

Both checked out okay.

I guess it has to be the starter solenoid draining the power. Any suggestions on how to check while it's on the car? If I disconnect it and the battery drain goes away - then that's it - correct?

One other little thing - in the past whenever I disconnected the battery I would lose my clock and radio station settings (I think). I've noticed recently that I only lose my clock - but my pre-set radio stations are still there - even after disconnecting the negative battery cable for a day or two. Is that normal? Weird? A symptom?

 

There are still things connected to the starter solenoid. UNPLUG the alternator connector and see if the reading goes away.

BC

 

Okay I'm still trying to narrow this down. I started from scratch and tried all your suggestions again.

This time I am still getting .106 amps at the battery. And .092 amps at the alternator as per your suggestion quoted.

But with the alternator disconnected I still get .106 amps at the battery.

So is the alternator bad as I'm not getting zero amps?

Or is it the starter causing the draw?

As always I really appreciate your guidance.

 

Well,,,,,,,,,,,, If you disconnect the ALTERNATOR from the circuit,, what is the total current draw at the battery??

I have NEVER seen a starter or solenoid draw ANY current other when they are starting the engine BUT,,,, stranger things have happened. You would be the FIRST.

To test that theory, you would have to disconnect the wires on the starter and see what the total current draw at the battery is.

That would be my absolute last culprit as the current grabber.

Bill

 

This looks like as good a place as any to put this.

So yesterday, I got in my car to leave work, turned the key, and the engine wouldn't turn over. You could hear the starter trying, but it just wasn't happening. Turned the key back to the off position, gave it another go, and it worked. Didn't have any problems with it for the rest of the night.

This morning, I got in, drove to a place about an hour away, and parked on a hill (I have no idea if this is significant or not). I came back about 25 minutes later and tried to start it. Same problem as the previous day. Tried turning the key to the off position and then trying again, and nothing. Tested the battery (it's 2 months old, but I figured what the heck) and it read at 12.45v, so nothing wrong there. After reconnecting the terminals and getting back in the car, I got the CHARGING SYSTEM FAULT message along with the LOW VOLTAGE MESSAGE and the internal volt meter on the dash was reading about 5-6v. Tried disconnecting and reconnecting the battery terminals again, and nothing. For some reason, the PCM wasn't throwing any DTC codes.

When the tow-truck driver finally showed up, he had me try it again. This time it worked for some reason (figures). On the drive home, the electrical gauge was reading about 14, so I don't think there's an issue with the alternator. Decided to stop at Advance and bought some electrolytic grease to slap on the terminals. When I put that on and re-tightened the bolts, the dash wouldn't even fully light up, but you could hear the relays in the BCM clicking on and off repeatedly so long as the key was in the on position, though). Bought some terminal cleaner and some steel wool and went at it the terminals and the connectors for a bit and got back in. This time, it did almost the same thing except that the "Corvette" in the DIC would start to display before disappearing (it would repeat this along with the clicking). After a few seconds, though, everything finally lit up and I was able to start the car.

Drove over the Firestone, where the guy told me that he could take a look at it on Monday, got in to drive away, and this time it did the same thing with the display beginning to boot before resetting and the BCM clicking, but for a much shorter period of time before starting. Got home, parked it in the drive way, turned it off and then tried turning it back on. No issues. Turned it back off, waited a bit longer, and turned it back on. No issues.

I'm going to try it again later at longer intervals, but I'm curious as to what might be the problem is here. Although it probably doesn't matter, I do have the LMC5 module installed.

 

WTH is a LMC5 module?

 

You either have a battery issue (Cell in the battery or connection in the battery is going bad) OR A loose/poor connection somewhere in the HIGH CURRENT battery wire portion of the charging/starting circuit. Any high current portion of the starting /charging circurt MUST be clean and tight and make 100% contact or it will get very hot and burn up or it will arc and stop flowing current. Sounds just like what yours is doing.

Check the battery terminals. They M U S T be properly TORQUED to clean and undamaged battery post. Proper torque for a 97-03 C5 is 11 ft/lbs!

The wires on the starter MUST be clean and tight..

BC

 

Bill, just wanted to say thanks for all the great info you've shared over the years. I just got done installing a cam in my 01 coupe with some friends.

Of course, it wouldn't crank. I told my buddy (he was doing the majority of the work, lol) that we should check the grounds as that can cause a no-start condition. He was convinced it wasn't a grounds since we didn't mess with them when doing the cam.

After he checked all the fuses, and consulted all the wiring schematics he could find, we pulled the intake. Sure enough, the G107 on the back of the driver's head broke off. We reconnected it and it fired right up!

Thanks to all on the site for the contributions - it is invaluable!

 

Its great when it all comes together,, isnt it!

Glad I was able to pass on some knowledge.

Bill

 

Soon after you replaced the battery? You noted that it is just 2 months old?

 

They just started this week, really. I guess I can take it in to Advance to have them look at it.

 

So this is odd. I've been able to correlate the P1518 code to the problem with the fuel level sensor that I've had since I bought the car (the one where it freaks out once the pump starts pushing fuel between the two tanks and causes the gauge to flat line on empty). When I clear the codes, I have no issues whatsoever. This would also explain why I have problems after driving for more than a half hour (the point at which the fuel issue arises) instead of around town.

I'm thinking that the corrosion on the battery terminals might have freaked out the diagnostic software, which is now incorrectly relating the bad fuel sensor to a problem with the electrical system.

 

Bill Curlee: I read with interest your posts (some of them) regarding the fuel sender problems you were experiencing on your Corvette. I also am experiencing that problem. I think my problem is the same as your and I was wondering if you ever were able to solve it.

My 02 convertible will randomly drop to zero within miles of a fill up. Then again it works fine. The damned thing is driving me crazy (short trip). For example, the last time I drove to Las Vegas (180 or so miles) it dumped on me twice. I stopped in Baker and used the code reader to clear the code and it was fine for a few miles. Coming home from that trip I topped off and it performed flawlessly all the way home until the next time I filled up.

This past weekend, I filled up before leaving town on the way to the 'Vettes for Vets car show in Carlsbad and within 40 miles it had done it again. I am at my wits end with this problem. I've even had the right sender out and inspected it. There appeared to be no mechanical malfunction there. I'm going to pull the left one as soon as I run the tank down a bit more.

I'm hoping that you have found SOMETHING to point me in the right direction. Thanks.

Jim

 

The DTCs thrown when it drops to ZERO will allow you to ZERO in on exactly what sender or SENDERS are bad.

"NORMALLY" a couple of treatments with Chevron Techron fuel system cleaner will resolve the issue. It just take a little time and a few tanks of fuel. Two treatments resolved mine but,, I have seen people use two Techron and two Seafoam treatments and resolve it.

All depends on how badly the sending units are coated with sulfur deposits.

You can also check the fuel sending unit ground G-401 on the drivers rear wheel section of the frame. Yours will be a stud .. Mine broke off and I had to use a screw:

 

Thanks, Bill. I have been the Seafoam/Techron route with absolutely NO results. I was hoping that you had found a mechanical problem, such as the ground, that cured it. I'll take a look at the ground stud and see what's up there. I appreciate your assistance. You would think that after, what, a hundred years of building cars, GM would have figured out how to make a decent electrical system. It's almost like they imported the engineers from Lucas. :-)

 

I continue to experience the flat line fuel gage. Here's my theory. The book says that the PCM monitors both L & R fuel gages and expects the right tank to empty first leaving 1/2 to empty in the left tank to run the engine. When the PCM detects an imbalance of a gal or so it triggers the gage to zero and sets a DTC code. With my car it's like clock work. At appoximately 28 miles (coincidently 1 gal) the gage trips. I believe my right tank sending unit jet pump is not transferring fuel leaving more gas in the right tank. When the left tank gets one gal lower then the right, the PCM flat lines the fuel gage. I may be wrong about this but after reading all the threads this is what I've concluded. Please fell free to chime in if my thinking is AFU. I am going to check the grounding stud and if that's OK then I'm going to pull the right sending unit. As much techron as I put in the tank, i should have bought stock. I would be a rich man by now. I get the code that says the right fuel sending unit is bad.

 

No, it would appear that the only thing that's AFU here is this stupid, over-thought fuel system. How difficult would it have been to just put an equalizing tube between the tanks with ONE fuel pump/sender? But NNNNOOOOOOO, they had to put in jet pumps and all the other crap that doesn't need to be there. The old KEEP IT SIMPLE STUPID concept seems to have been lost on the engineers at Corvette. I'm in the process of burning down the tanks so I can pull the left sender out and take a look at it. I think I'll also pull the right one out again and do a resistance check on both. If I can ever get this problem solved I might be happier with the car.

 

Spooky. What is leading you to pull the left sending unit? Are you getting a left tank code?

 

Nothing in particular, other than curiosity. The right one was easy to get out and replace so I figured, "What the heck. Let's take a look at the other one." I checked my ground stud and it is good. I'm going to fix this SOB if it kills me....and it probably will! :-)