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Thread: Trouble codes

  1. #1
    Join Date
    Feb 2012
    Location
    new jersey
    Posts
    17

    Default Trouble codes

    ok i have a 95 xj 2wd 4.0 i have no check engine light. but i just got a new obd1 reader so to test it out i hooked it up i got 6 codes. 4 codes and 2 duplicates. i got 21 42 43 and 47 i know what the codes mean but my question is y isnt the light on? yes the light works. im thinking they are saved codes. it already has a new alt. and battery any suggestions.

  2. #2
    Join Date
    Nov 2011
    Location
    Cyprus
    Posts
    209

    Default Re: Trouble codes

    You don't necessarily have to see the CEL come on to register fault codes in the PCM. I suggest you disconnect the battery for at least 10 minutes to reset the PCM, go for a 20+ minutes drive, and then scan the PCM again to find out if any of the previous codes reappear.

    21 Oxygen sensor signal doesn't change (stays at 4.3-4.5V). Probably bad oxygen sensor
    42 Automatic shutdown relay circuit open or shorted
    42 Fuel pump relay control circuit
    42 Fuel level unit - no change over miles
    OR
    42 Z1 voltage missing when autoshutdown circuit energized (SEE NOTE #6)
    43 Peak primary coil current not achieved with max dwell time
    OR
    43 Cylinder misfire
    OR
    43 Problem in power module to logic module interface
    47 Battery voltage too low and alternator output too low

    1992 XJ - 4.6L Stroker - AX15 - Sold 13/12/2016
    202rwhp 258rwtq (248bhp 311lbft crank)
    Jeep Performance, Jeep Tech, Junker to Stroker

  3. #3
    Join Date
    Sep 2009
    Location
    Chico, CA
    Posts
    29,847

    Default Re: Trouble codes

    Clear the codes and see what happens. If you get all those codes again instantly, then the ECM is starting to breath its last.
    230 hp 4.3L Chevy
    Built 4L60E with manual lockout
    Atlas 4 speed
    Griffin radiator
    On board air
    Warn 9.5ti on custom bumper
    7.5" RE front and bastard pack rear on custom long arms
    30 gal gas tank
    lockers
    And a bunch of other stuff

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