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2007 Pontiac G6 2.4 charging problem

Less than 60,000 miles on this ride and occasionly the “idiot light” for the charging system would come on then go off. It wouldn’t even store a fault code for my scangauge to pull. Today while pulling into a parking lot the steering (electric) went out when the car died jerking the steering wheel out of my hands.
Jump started and this time the “idiot light” was on my scangauge showed a low voltage of 8.1 volts. But NO stored fault codes again! Why won’t it store any fault codes?
Going to pull the alternator off tomorrow morning and have it checked. The battery is on charge and is almost new which shows it’s taking a charge and slowly building one.
If the battery is good and the connections at the terminals are good can it be anything else but a faulty alternator?
What a pickle this is.

A bad connection, terminal or cable come to mind.

If its a bad alternator which is highly likely, I would highly suggest getting the AC Delco rebuilt or new. The new ones have a lifetime warranty and the rebuilts are just like new with all the parts that are replaced. They cost a little more but you get a quality product. Been there done that and saw the light.

Just drive the car to an auto parts store where the system can be tested for free without removing anything from the car.

My own scangauge shows low voltage and from what I’ve heard the only true way to test an alternator is to remove it from its system and bench check it. It’s an intermittent charging problem which is not storing ANY fault codes. If it did, the problem would be self-explanatory. Thanks for the all the tips.

You can test the alternator by using a simple voltmeter or multimeter. Take a voltage measurement of the battery with the engine off. It should be around 12.4 volts or so. Start the engine. Take another reading of the battery and if it shows about the same as the original battery reading then it’s time for a new alternator. The auto parts store can do this for free.

I would get this problem addressed immediately. If the battery goes dead or the alternator shorts out (which is possible) you can do very expensive damage to the electronic components of your vehicle.

Just returned from a reputable alternatior/starter rebuilder. No national brand auto parts could test the alternatior from a 2007 Pontiac g6 2.4. Didn’t have the adapters. Anyway, the rebuilder did check it and it turned out ok and the brushes had little wear. The battery showed it was good but I noticed one of the cells was a little low and the acid had been pushed out of the cell which made the bottom of the battery case a tad bit wet. Again when tested it was ok.
At this point I’m thinking about changing the battery (side post) with a new one. Mine is only 18 months old. BTW all connections between the battery (plus and negative) have been removed and cleaned. No obvious corrision areas observed.
What a pickle this has been.

I think I would change that battery. Even if this don’t fix your problem. The battery should not leak. It could be that the cell thats leaking could be the problem too. If that cell shorted it may have caused the car to die. I have seen shorted battery’s do strange things. I had one that would test good (load tested) but would not start the car even with a boost. I would have the electric steering checked out also. It may have a short in it or maybe going out.

Really don’t think it’s the battery leaking but more of a boiling over. Guessing now that the battery drops its voltage-perhaps a short-and the alternator kicks in hard to compensate by charging.
Again, no stored fault codes. Another guess is that there is no technology on my G6 recording the condition of the battery but only what charges it. Am I right?
Purchasing a new battery tomorrow.

The battery light is really misnamed as it normally tells of a problem with the alternator.

I’ve never heard of an alternator or battery that sets a code when it fails but things change so who knows.

If your voltage really was at 8.1v then you were not charging. At rest a car battery should have 12.6 volts at least and when the car is running it should be higher than that, normally I would say between 13.5 & 14.5 volts.

If the battery is boiling over that would indicate an overcharging in the system.

How is the voltage regulated in this system? Is the regulator internal to the alternator or does it regulate through the computer?

If this is an intermittent problem the testing that was done at the rebuilders may not be conclusive.

Dealership did a diagnostic. THEY pulled a fault code while my scangauge did not. The alternator does put out the voltage but a gizmo inside of it does not tell the ECM that it does so the battery will not accept a charge. Alternator will be replaced. For those of you keeping score, a bench test does NOT reflect the accurate condition of the alternator only a part of it.

Changed alternator and that’s the fix! Took 2 days to locate one so the bottom line is that a BENCH test does NOT always give an accurate reading of an alternator. Some can only be tested accurately while on the vehicle.

This signal from the alternator to the ECM is a relatively new thing, in as far as the ECM is a relatively new thing too.
Traditional testing of the alternator is centered on the parts that fail most of the time: brushes, diodes, internal regulator etc.

Keep an eye on the cell that had the low level. It sounds like there is a possibility that the cell may be shorting out and boiling the acid out of it.

Error codes generally pertain to the engine operation for control of emissions. The operation of the alternator doesn’t effect emissions.

Would like to know exactly what the part is inside the alternator which tell the ECM to accept the charge to the battery. Is it a circuit board or computer chip? Anyway I went to school on this caper.
Did change the battery out with a new one. Didn’t trust it after it boiled over even though it might have been a failing alternator which caused it.

Your vehicle actually doesn’t have an alternator but instead a DC generator. And the voltage from the generator is controlled thru the engine management computer.


Hmmm, still wondering what inside the alternator is faulty. Remember, it checked out good twice by a rebuilder. After all the ecm had no problem.


The generator doesn’t have a voltage regulator, and it doesn’t have a rectifier/diode assembly. If you look at the generator connections you’ll see B+ which is battery supply voltage, F is generator field duty cycle controlled by the ECM, L is generator turn on signal controlled by the ECM, and S & P connections aren’t used.

If you’re still having problems with the charging system, then the ECM is the next suspect.


tester, when and why would GM go back to generators?