Battery voltage gauge drops?

Hi,

It sounds like either the alternator is failing, there is an error with the gauge, or the PCM is failing.

Here is what I recommend. Let's check something at home. All you will need is a voltmeter or multimeter. Follow the directions in this link and let me know the results.

I'm questioning the gauge because even if the alternator isn't charging, the gauge should still indicate battery voltage and not 0. Do this and let me know.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Let me know what you find.

Take care,

Joe

The codes he found are for the oxygen sensors and have nothing to do with the charging system. In this case, if the voltage is going to 8v, the alternator is not charging at that point.

The battery is 12v. Usually, you will see that voltage or near that voltage when the engine is off. When the engine is running, checking the voltage of the battery should be around 14v. If you are seeing 8, then we have a problem.

In most cases, it isn't a wiring issue, but instead, it is the alternator or voltage regulator that is failing. On this vehicle, the voltage regulator is integral to the powertrain control module. As a result, my first suspect of failure is the powertrain control module. That is based on the same thing happening with the new alternator as did with the original one.

Let me know your thoughts and if you have questions.

Take care,

Joe

Hi,

If the battery fails while driving, it will shut the vehicle off. That is a tough question to answer for you. I say that because if the battery isn't fully charged and you use any of the electronics, it will cause the battery to fail faster.

Will you hurt the vehicle? I don't feel it would. My concern is that you won't make your destination.

Let me know.

Take care,

Joe

PS: Also, before making the purchase for a new alt, remove your old one and have it bench-tested at the parts store. They will do it free of charge. I suggest this because the issue can be the alternator, a wiring issue, or the powertrain control module.

Hi,

If the alternator isn't charging, the PCM is the likely problem. On most vehicles, the voltage regulator that controls the alternator is integral. On this vehicle, the voltage is regulated by the powertrain control module (PCM).

I mentioned above that either it would be the alternator or the PCM. If you want to confirm that, remove the alternator and have it bench-tested by the parts store. If it is good, the PCM is the likely cause.

So, we have two ways you can repair this. First, you can have a shop or dealer sell you a new PCM and then charge you to program it to your vehicle. That will be somewhat expensive to have done. Or you can purchase a remanufactured PCM online that is plug-and-play. They will need your VIN number and when you install the new PCM, you will need to send back the old one. As I mentioned, I've gone this way and have been very happy with the results. Simply, disconnect the negative battery terminal, remove and install the new PCM and it's done. Just make sure you are getting one that is already programmed.

I have done this on my personal vehicles simply due to the cost. The last one I did was on a Dakota and the remanufactured part was 129.00. I know that's a lot, but to go the other way would likely be close to 1000.00.

If you look at the pics below, it shows the location and removal procedure for the PCM. The very last pic shows the parts and labor if you go with a new one.

Let me know your thoughts. Also, when I read back through the thread, I noticed that when I indicated it could be the alt or PCM, you took it to a parts store, and they scanned the computer. They needed to test the charging system. That's why you were unaware.

Let me know what you decide and what I can do to help.

Take care,

Joe

See pics below.

You aren't bothering to read Joe's replies or you would have had this solved already. It is not the alternator, so why are you still looking at it? A few simple voltage tests on that two-wire plug would have shown which direction to start the diagnosis rather than wasting money on unneeded parts.

The charging system that keeps the battery charged is made up of a half dozen parts with wires and connectors between them. Any one of those parts can cause this problem. You tried one of them already. Now it's time to figure out which one of the other parts is at fault.

I want to know the solution. Please don't keep me in suspense.