Service Engine Soon light

I recently had my battery die in my Pathfinder. When the new one was installed the Service Engine Soon light was on and has been ever since. Any idea why this would be?

The OBDII readiness monitors haven’t reset.

Anytime a battery is disconnected or dies in todays vehicles, the monitors for the various input signals to the OBDII system are lost. This means the vehicle needs to be driven under what are called “Drive Cycles” to reset the monitors. But most times normal driving of the vehicle will reset the monitors. However, there are some monitors that require a certain drive cycle before they reset.

So drive the vehicle for a while, and see if the Check Engine light goes out. If it doesn’t, then a scanner should be connected to determine what monitor hasn’t reset, and then drive the vehicle under the conditions that resets that monitor.


Thanks so much!! Will try to not worry and just drive a while-hopefully it wil resolve itself! Appreciate your input.
Take care,

Tester, the ‘Service Engine Soon’ light is on because there is a trouble code. The fact that the monitors are not ready doesn’t turn on the SES.

BrittC, go back to the shop that put in the battery, and see if they can pull the codes for you. It may be related to the dead battery, but probably something else.

Thanks for your input, BustedKnuckles. Think I’ll compromise and give it a day or two. I’ll take it in if still lit up on Monday, does that seem reasonable? :slight_smile:
Not sure what “pull the codes” means, but I’m sure they’ll charge for it. I’m a single Mom, not a lot of cash flow (new battery cost $70!!). Thanks again!

My battery died suddenly in my 2004 F-150 (like overnight) and I never experienced a “check engine” light.

Some auto parts places will check the codes for free. Record the exact code, not just what the technician says they mean. Question here again with the code(s). Pull the codes means to use a scanner to check for codes. The scanner will also tell what monitors are not in ready status, if any. It takes about half a minute to check. Usually, there is no dashboard disassembly required.

Good to know there are places that will do this for free. I will do some research to find one in my area. Thanks for the clarification on pull the codes, appreciate that! :slight_smile:

Usually, it’s one of the auto parts chain stores (Auto Zone, Pep Boys, Advance, etc.) which will do a free scan (except in California). Ask the tester to “erase the codes” after they are read. This is to turn off the check engine light. If the problem is still there, the check engine light will come back on, and the codes will return. Repeat test, etc. Hope.

There are times that even after a problem is corrected, the light will remain until it has completed X number of drive cycles.

That is some good info-thanks! Was hoping it would resolve itself, but still on this am. Will take it somewhere on Monday. Thanks for your help, hellokit. :slight_smile: