How can an engine code clear itself?

litewait · Post by **litewait** » 23 May 2020, 08:25

See my other post about my S80 throwing P2135, the code cleared itself somehow. Why would that be?

Post by **SuperHerman** » 25 May 2020, 21:46

Basically codes are of three types 1) Actual part has failed (code will not clear until part/sensor replaced); 2) intermittent failing part (code will come and go); or 3) code caused by the computer reading an issue which has resolved itself.

Possible causes for a generic P1235 code are: Faulty Fuel Pump or related module; sensor or related wiring is open or shorted; bad wiring in the circuit, or another faulty module

Your issue could be either 2 or 3 - maybe bad gas or some debris in an injector that was cleared via use. I would keep an eye on it and see if it comes back. One thing about generic codes (not VIDA or Volvo scanner specific) is many false codes.

Post by **MoVolvos** » 26 May 2020, 20:35

I believe every car should have a drive cycle where the computer checks for faults. As Super says if the computer sees that the reading is Okay it will remove the light / fault code.

Post by **ndphotonl** » 27 May 2020, 09:10

If you check it with DICE, it will probably still be referenced over there. Not all codes are visible with something like Torque Pro app or a universal code reader.