Well this one threw me I have to say! Jeep Cherokee 2.4 petrol came in with the Engine Management light on.

Code reader came up with code P0133 which relates to O2 sensor bank 1 sensor 1. Tested readings from sensor which were all ok. A brief check over revealed no issues, so suspecting just a “spike” in the system I cleared the code and road tested, all OK.

Until 2 days later when the customer returned with the warning light back on. Not unusual  I guess, so after re checking the code came up the same again P0133.  Again after carrying out checks all was clear. However decided to replace the O2 sensor, clear code road test…etc.

Guess what! 2 days later customer returns with the damn engine light on again! Same code same issue!

Now I went deeper into the diagnostics, checked and double checked everything. No faults found at all! Even considered replacing the new O2 sensor, which was genuine part, in case that was faulty.

Customer called for an update, told him what I could and he started telling me about he had heard about fuel cap issues, yup you guessed it I shot him down in flames! How could it be the fuel cap…blah..blah. But he insisted I replace it.

Well how stupid did I look when it worked! After doing a bit of research of my own it appears this is a know issue with these vehicles!! Yup, it appears that if the fuel cap has a poor seal then it will throw up the warning light with that code!

So now we know…