How to reset Check Engine light by disconnecting battery

[Keith Shelnutt]

2020 Rubicon, I had a check engine light come on and tried to reset it by disconnecting post on main battery, I disconnected the positive and negative post and left disconnected for an hour and still had power to system. What else do I need to disconnect to achieve goal.

Sponsored

 

[Hootbro]

That does not necessarily reset the MIL if the code is a hard set fault. Also, unless the aux battery was disconnected, there still may be power. This is were a cheapie $20 and sub priced OBDII scanner is worth the investment.

 

[Figmo]

No curiosity as to "why" the check engine light came on in the first place? I guess just ignore it and it goes away? Kinda like those chest pains you get.


But since you're asking, I'd advise you have either of these checked out. Agree with HootBro - get a OBDII scanner. Not only will you be able to turn off your CEL (with no need to disconnect battery) - you'll also have an idea as to the reason why it was on in the first place.

And be able to make an better informed decision on what to do next (if anything)

 

[Keith Shelnutt]

I had auto parts store run a scan, it came up with P0128 (Coolant Temperature below Thermostat Regulating Temperature) He said he could not reset fault code. so I bought a scanner and did it myself, I was just wondering were aux battery hooks up to kill power to see if it would reset fault before buying scanner. I'm a poor man I own a Jeep. I need to get me a wiring diagram I suppose just thought one of you Jeepers would know. Thanks anyhow.

 

[Lost1wing]

Now that you have disconnected your main, leaving your aux powered, I would expect that you will have another problem to arise. A power up test may sense a difference with your main and aux battery, leaving you with ess battery charging or unavailable. You may want to charge your batteries and reset the IBS. Or just wing it and see what happens. You could alway revisit here and get instructions on what to do. I would suggest reading up on charging your batteries before attempting it.

 

[Lost1wing]

I had auto parts store run a scan, it came up with P0128 (Coolant Temperature below Thermostat Regulating Temperature) He said he could not reset fault code. so I bought a scanner and did it myself, I was just wondering were aux battery hooks up to kill power to see if it would reset fault before buying scanner. I'm a poor man I own a Jeep. I need to get me a wiring diagram I suppose just thought one of you Jeepers would know. Thanks anyhow.

I am not familiar with your code. Many newer obd codes are either pending, current and permanent codes. You can erase pending and current codes with a scan tool and by removing the negative cable at the fender ground. Permanent codes will clear when the problem is corrected.

 

[Keith Shelnutt]

Thanks, That's exactly what I needed to know this morning, after looking at a wiring diagram this would kill the main and aux battery to the system. Have a good day.

 

[ross neill]

You have two batteries main, aux it’s easier to by a scanner to delete codes it’s a pain to disconnect the auxiliary battery

 

[Keith Shelnutt]

What is the highest engine temperature have yall seen like setting in traffic with auto start turned off

 

[Bbannongmu]

You have two batteries main, aux it’s easier to by a scanner to delete codes it’s a pain to disconnect the auxiliary battery

The aux battery negative is in with the main battery negative. You undo all the connections on the negative cable side and it’s disconnected. There are things that require a complete disconnect of the battery and a relearn after the code is cleared. YMMV. Good luck.

 

[ross neill]

When my starter was replaced under warranty they had to open up wheel well to disconnect auxiliary battery

 

[Minty JL]

I am not familiar with your code. Many newer obd codes are either pending, current and permanent codes. You can erase pending and current codes with a scan tool and by removing the negative cable at the fender ground. Permanent codes will clear when the problem is corrected.

∆∆∆ This

 

[Bbannongmu]

When my starter was replaced under warranty they had to open up wheel well to disconnect auxiliary battery

That’s a way to do it but not the only or easiest way. The negative cable from the aux battery attaches to the negative for the main battery with a common ground. Break that connection on both sides by disconnecting the cables and you break the circuit for the vehicle. I did it here after a regear

 

[Freems]

I had auto parts store run a scan, it came up with P0128 (Coolant Temperature below Thermostat Regulating Temperature) He said he could not reset fault code. so I bought a scanner and did it myself, I was just wondering were aux battery hooks up to kill power to see if it would reset fault before buying scanner. I'm a poor man I own a Jeep. I need to get me a wiring diagram I suppose just thought one of you Jeepers would know. Thanks anyhow.

Sponsored