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how to clear computer codes ?

Discussion in 'General Chevy & GM Tech Questions' started by RATRODKING, May 18, 2013.

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  1. RATRODKING

    RATRODKING New Member 100 Posts

    guys, i have a 1990 k1500 with 5.7 v-8.
    to clear all check engine light codes, is it enough to just remove the positive battery cable for a few minutes, then reconnect ?
    i just ready online someone suggest pulling both battery cables, then turning on the inside interior light, to discharge all stored power, then reconnect.
    is all the really necessary ?
    thanks guys
  2. kinson33

    kinson33 New Member 100 Posts

    do you already know the cause of the codes?
  3. RATRODKING

    RATRODKING New Member 100 Posts

    yes, it was a 42 code, ignition module or ecm... i changed the module and although it wasnt flashing the check engine light, when i would do the jumper wire it would still flash the 42 code.

    i bought a manual and it said to pull the IGN fuse from the fuse block.. i did that, and the code is no longer there.... so i got it cleared, thanks.

    me changing the ignition module cured the initial problem of it running a little rough from time to time, and major bucking last sunday morning, but three times this week it has stalled on me, either when putting it in gear from a dead stop, or once setting at a traffic light.... its driving me crazy. but i now have the code cleared and can now see if it comes back.

    i wonder if me not having cleared the code initially would have had the irratic effect even though i put the new module in ? i doubt it... gonna see what happens in the next week or so.
    thanks again
  4. kinson33

    kinson33 New Member 100 Posts

    Cant imagine not clearing the codes before you fixed it would cause that. Hope it smoothes out, let us know how it goes
  5. PhillipL

    PhillipL New Member

    You said something about the check engine light flashing? That is a class A misfire.. Could do some damage there.. Also, clearing the code does not solve any problem.. Codes and the MIL are set when there is a problem that needs to be addressed, most often something wrong with the emissions system.. Obviously if you were having issues after you changed the ignition module, that wasnt the only existing problem... The next time a code is set take it seriously and know that disconnecting the battery or pulling a fuse only turns off the light and doesnt fix anything..
  6. kinson33

    kinson33 New Member 100 Posts





    Doesnt sound like a misfire
  7. RATRODKING

    RATRODKING New Member 100 Posts

    thanks for the input guys...much appreciated...
    the check engine light last sunday was constantly on, sorry for the mistake.. it wasnt flashing..

    so far, since i have cleared the code yesterday it has not come back on and is running fine...

    thinking back, this is the third ICM i have installed on the truck, and looking in ym manual, code 42 says ignition module or ECM.

    so..... if i get that code again, i will replace the ECM thats under the dash board.... in doing so i have learned that i will have to pull my vehicle specific PROM chip so it knows my vehicle specifics...

    man, i miss the older trucks that i could diagnose just by listening to it...
    the truck runs so darn good for 23 years old, and only having 161k miles... i would hate to get rid of it at this point, but i cant be keep being let down by its erratic stalling...
    i will let you know what happens in the coming weeks... hope it just stays running good.
    again, thanks for your input.
  8. kinson33

    kinson33 New Member 100 Posts

    Could always pick up an old model and rebuild haha

    Sorry couldn't be of more use. Hopefully there is a tech checking around that could chime in. Hope it works out
    Last edited: May 20, 2013

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