Check Engine Light on after Replacing BOTH Batteries?

[LSUjeep]

Hi guys - my wife has a 2023 Wrangler and it would not start the other night and lit up a thousand different lights on the dash when trying to start it so we had the main battery replaced and it started and ran fine and then got the auxiliary battery replaced the next day. Have had no issues since for about 5 days. Well this morning the check engine light is on and just staying on. Brought to dealership and they couldn't see her today but ran the codes and every code came up with something related to the battery. Brought it to Firestone where the auxiliary battery was replaced last week and they unplugged both batteries checked them and reset everything. No code now but they didn't see anything wrong. Anyone know what this could be causing the light? It is off now and they said it is not coming back on currently. Thanks for any suggestions.

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[Blacksport]

First thing...get your own OBD2 scanner. Even a cheap one will read and reset codes. Sometimes resetting a code gets rid of it and doesn't come back. This one is $15 on Amazon...

 

[Terrymo]

@Blacksport has it right. Otherwise, by not telling forum members any diagnostic trouble codes, you’ve left out the most important information, and you’re just going to get a lot of guesses here.

 

[LSUjeep]

@Blacksport has it right. Otherwise, by not telling forum members any diagnostic trouble codes, you’ve left out the most important information, and you’re just going to get a lot of guesses here.

It was a low voltage code. P-0652. The Firestone place reset the code and checked all the batteries. They didn't see anything wrong. Code has not come back now.

 

[IndyTom]

• Shorted Sensors: A malfunctioning sensor (e.g., Throttle Position, MAP, or Oil Pressure sensor) drawing too much power.

• Damaged Wiring: Frayed, pinched, or corroded wiring harnesses that are shorting to ground.

• Moisture Damage: Water intrusion in electrical connectors causing a short.

• Failed ECM: Rarely, an internal failure within the ECM's voltage regulator.

 

[THAW]

It was a low voltage code. P-0652. The Firestone place reset the code and checked all the batteries. They didn't see anything wrong. Code has not come back now.

It sounds possible they didn't tighten the battery terminals properly the first time.

 

[LSUjeep]

It sounds possible they didn't tighten the battery terminals properly the first time.

That's what I'm hoping. They said they disconnected and then reconnected everything.

 

[The Last Cowboy]

A blown high amp fuse array is the most common issue when this happens. The fuse array is easy to blow, just one spark can do it. It will keep the batteries from charging, and you will likely be unable to start it in just a few days.

You can confirm by removing the high amp array, and checking each post with a multi meter. The part runs about $80. There two different ones. One for the 220 amp alternator, and one for the 200 amp alternator.

Ideally, you would have just replaced only the main battery with and H7/94R, and removed the auxiliary battery from the circuit by disconnecting it's ground, and removing fuse 42.

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