Hey all,
I have a 2024 Mazda CX-5 (leased). Last week I accidentally forgot to put the gas cap back on after fueling. Shortly after, the check engine light came on. I scanned it with an OBD2 scanner, got a code, and cleared it.

Now the light is back again, but this time I'm getting:

P0171: Powertrain Control Module (PCP)


No EVAP code showed up, which is what I’d expect from a gas cap issue. I did reset it again, but the P0171 came back. Car runs fine, no noticeable performance issues.

Do you think this is still related to the gas cap or more likely a vacuum leak / MAF sensor problem? Would this be covered under warranty since it’s a lease?

Any help or shared experiences would be appreciated. Thanks!

 

The check engine light acutes when the ECU has an unresolved problem. Clearing a DTC only turns of the check engine light from seeing it and removes it from the pending file in the ECU. If you looked in the permanent file the DTC remains while the engine cycles and if the original unresolved cause of the ECU is not corrected the check engine light is reactivated again.

A DTC does not always mean to replace a part but give the Tech a starting point to begin looking for the cause.

I recommend if you don’t have a quality direct connect access to the Dignostic oBD connector and can access at least the 3 important information areas of the ECU that you contact the dealer regarding your current warranty status. Replacing parts if you are under WARRANTY COULD NEGATIVELY effect your warranty status unless your are a Mazda trained mechanic or current ASE Master Automotive Technician. But then if you were either you would be writing this response .😉

You can guess you answer to your problem and must start a problem solving chart or tree and start testing .

So let’s say you are a confident DIY with a scanner as I described?

Note the current active DTC
Go to permanent file Note the any and all DTC
Go to I/M Monitors note which are in fault or not ready status

Now you can clear the DTCs

Do this at night when the engine can completely cool down as to start a new cycle on your new day starting your engine. Start the engine and when it reaches operating temp. drive and as soon as the engine check light is activated pull to a safe area off the road and scan the ECU in the 3 areas again making notes of the DTC s and I/m status. This will give you the first area to check for part failure or connect ability of the part. Then you can either check the part or take a chance and replace the part hopping it actually was the cause. But randomly replacing parts without first verifying that they failed can and often does create new issues added to the original unresolved issue.

As for the gas cap….test by way of applying a little Vaseline on the o-ring seal
.

 

Welcome to the forum 007 Harry …

 

thank you!!

 

Thanks for the detailed breakdown—I really appreciate it. I’m definitely not planning to replace any parts myself, especially since it’s a lease and still under warranty. I’ll go ahead and call the dealer to have it checked out properly.

My only concern is that they might try to open a can of worms and charge me if they claim it’s not covered under warranty. But I guess it’s better to be safe and have it properly diagnosed.