Check Engine light - Code reader not finding anything

[rick619]

I have a check engine light and my code reader is saying no codes found.

I had a check engine a few months ago and the code reader was able to read it then, cylinder misfire. Got that fixed under warranty.

So I've tried with the engine power in all 3 positions, engine off and engine on. It's still saying no codes found. Not sure what I'm doing wrong. I checked youtube and didn't find a good video showing the proper procedure.

 

[2025 Ram Limited]

I had mine come on on Monday while cruising down the highway. Everything seemed to work as normal and then yesterday morning it went off. Some think it could be signs of a battery going bad. I have had the truck for a year now and this was the first time.

 

[John Kloehr]

Some (most typical from auto parts stores) only read P codes, the light could be due to a code in a different system (B, C, or U codes). Also some will only read active, not pending, codes. But if the dash light is on, there is an active code.

Anyway, key in engine-on position should be fine for all cases.

 

[2025 Ram Limited]

Some (most typical from auto parts stores) only read P codes, the light could be due to a code in a different system (B, C, or U codes). Also some will only read active, not pending, codes. But if the dash light is on, there is an active code.

Anyway, key in engine-on position should be fine for all cases.

So when the light went off by itself that means it cleared the code on it's own? With all the electronics on these trucks it seems odd.

 

[LaxDfns15]

So when the light went off by itself that means it cleared the code on it's own? With all the electronics on these trucks it seems odd.

The event that caused the code could have gone away, but the code should still be stored in the system. It just won't be active.

 

[rick619]

Some (most typical from auto parts stores) only read P codes, the light could be due to a code in a different system (B, C, or U codes). Also some will only read active, not pending, codes. But if the dash light is on, there is an active code.

Anyway, key in engine-on position should be fine for all cases.

The check engine light was still there this morning. It is ready for an oil change, not sure if that would cause a check engine?

I tried the code reader again when I got to work. Still saying no codes found. Really odd.

Seemed to drive like normal on the way to work, so not likely a cylinder misfire again. I was likely going to an oil change place to have that done. Now probably just have it done at the dealer. It's a '23, but I bought it new in '24 almost exactly 2 years ago. So still under warranty at 15K miles.

 

[rick619]

I had mine come on on Monday while cruising down the highway. Everything seemed to work as normal and then yesterday morning it went off. Some think it could be signs of a battery going bad. I have had the truck for a year now and this was the first time.

I did have an issue with it not starting around a year ago. AAA said nothing wrong with the battery. The dealer couldn't find any problems and replaced the battery anyway. So hopefully not that (though and easy fix).

 

[rick619]

I'm bringing it to the dealer Saturday.

 

[UnloosedChewtoy]

I did have an issue with it not starting around a year ago. AAA said nothing wrong with the battery. The dealer couldn't find any problems and replaced the battery anyway. So hopefully not that (though and easy fix).

Never 100% trust battery testers on the automotive batteries these days. I've seen many batteries "test fine" at the dealer and at retail stores, but yet the problems go away with a new battery. Ones that investigate further frequently discover bad cells or other parts of the batteries not working right, or being intermittent.

If voltage gets wonky at all, I just default to replacing a battery, regardless of what testers say. So many crap batteries out there with hit-miss quality control, even the good brands are not as good as they used to be (but still better than most), hate to say. Over on the TRX forums, many went for Enersys batteries (expensive), including myself, only to have many of those go bad in a year or two.

East Penn (Deka) seems to be one of the last good makers of mostly reliable units out there, and thankfully make batteries for many brands. Also one of the last ones that build them in the USA still.

 

[SW Driver]

The check engine light was still there this morning. It is ready for an oil change, not sure if that would cause a check engine?

I tried the code reader again when I got to work. Still saying no codes found. Really odd.

Seemed to drive like normal on the way to work, so not likely a cylinder misfire again. I was likely going to an oil change place to have that done. Now probably just have it done at the dealer. It's a '23, but I bought it new in '24 almost exactly 2 years ago. So still under warranty at 15K miles.

The check engine light is for emissions related issues, so has nothing to do with the need for an oil change. If the light is active, a reader should read the code when you plug it into the OBDII port. If your reader isn’t finding a code, perhaps something is wrong with it. Try going to AutoZone and have them read it.

 

[rick619]

Never 100% trust battery testers on the automotive batteries these days. I've seen many batteries "test fine" at the dealer and at retail stores, but yet the problems go away with a new battery. Ones that investigate further frequently discover bad cells or other parts of the batteries not working right, or being intermittent.

If voltage gets wonky at all, I just default to replacing a battery, regardless of what testers say. So many crap batteries out there with hit-miss quality control, even the good brands are not as good as they used to be (but still better than most), hate to say. Over on the TRX forums, many went for Enersys batteries (expensive), including myself, only to have many of those go bad in a year or two.

East Penn (Deka) seems to be one of the last good makers of mostly reliable units out there, and thankfully make batteries for many brands. Also one of the last ones that build them in the USA still.

Yes, many of the battery MFG's I used to trust are now garbage. I used to rely on Sears Diehard. Those used to give good value. Though that was when Sears was still around. AGM used to be the way to go if you wanted one to last. Not so much anymore.

 

[rick619]

The check engine light is for emissions related issues, so has nothing to do with the need for an oil change. If the light is active, a reader should read the code when you plug it into the OBDII port. If your reader isn’t finding a code, perhaps something is wrong with it. Try going to AutoZone and have them read it.

I'm taking it to the dealer tomorrow.

 

[RHO]

I have a check engine light and my code reader is saying no codes found.

I had a check engine a few months ago and the code reader was able to read it then, cylinder misfire. Got that fixed under warranty.

So I've tried with the engine power in all 3 positions, engine off and engine on. It's still saying no codes found. Not sure what I'm doing wrong. I checked youtube and didn't find a good video showing the proper procedure.

can your code reader , read all the modules like BCM , TRANSMISSION sorry about caps and other modules ?

 

[rick619]

can your code reader , read all the modules like BCM , TRANSMISSION sorry about caps and other modules ?

This is what I have. It's gotten me through many fun codes on my 04 and 06 Jeep Wranglers lol. I did read my cylinder misfire codes on the truck about a year ago. This is the first time I've seen a check engine light that it couldn't read.

https://www.amazon.com/dp/B07Z3HB7DR?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

• ABS / Airbag codes NOT Supported - It is able to read and clear check engine information which is part of OBDII system, but it cannot work with non-OBDII systems, including ABS / Airbag / Oil Service Light, etc.

I did get a light that an oil change is due soon. Not sure if that would cause a check engine?

The light was on yesterday when I drove to work. Then when I started the truck to go home, it had turned off. Sure enough, turned on again about 20 min later.