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Thread: Error codes 42 and 45 on '89 sierra what is this

  1. #1
    Full Member
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    Aug 2010

    Error codes 42 and 45 on '89 sierra what is this

    So as the title reads I have these codes...i recently attempted to smog my '89 w/ 350 tbi...which it did not pass registering high HC....prior to bringing the truck in for testing it had a bit of a rough idle upon stopping at traffic it seems to run rough as i step on the gas and intermittently cuts out...smog people they didn't fuss w/ anything seems like bs...anyways here what I've done the truck recently.

    1.New O2 sensor
    2. New map sensor
    3. New IAC
    4. New distributor,cap, wires, rotor ignition, control module, plugs
    5. Throttle Positioning Sensor
    6. Thermostat
    7. Temp Sensor
    8. Egr Valve

    Any much more that I probably can't remember.

    Any help would be really appreciated...I'm throwin out a lifeline here. Thx in advance.

  2. #2
    Senior Member zombie1969's Avatar
    Join Date
    Jun 2010
    From what Ive found 42 has something to do with when the ecm is trying to change the timming and the modual doesnt respond.Could be a bad ignition modual.45 is because the o2 is reading a rich fuel mixture and could be possably conected to the code 42 problem.There are other things that could cause a rich condition but I would fix 42 first and go from there.
    (edit)Seeing you replaced the modual check the wiring and get a flow chart to make things easier to figure out.
    Sent using Boost mobile 4g htc evo.

  3. #3
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    Aug 2010
    Being a bit green around the gills..flow chart? New ignition module...have replaced twice...what is the ESC(Electronic spark control circuit)....seems to be the explanation in the code reader book...Timing is at 0 TDC. IN the past the 42 code, 44, 45 codes, and even 32 codes have all popped up at one time or another...hence replacing all the above. Thx for advice

  4. #4
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    leolkfrm's Avatar
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  5. #5
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    Aug 2010
    i believe it was the 180 thermostat...replaced about 3 weeks ago. LIke I said truck began running super weird after the smog check.
    What is the IAC reset?

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