Codes 24, 42 and 75 please tell me what to do.

Discussion in 'The Garage' started by afroman006, Feb 4, 2004.

  1. afroman006

    afroman006 1/2 ton status

    Aug 21, 2002
    Likes Received:
    College Station & Kingsville, Texas
    I just had a new distributor put in the burb because it was running horribly and I suspected the old distributor was the culprit. I was right, it runs great now but my idiot light keeps comin on so I took a code reading with my scanner tonight and got the following results.

    Code 24- Vehicle speed sensor short circuit
    Code 42- Ignition system problem. Elec spark timing circuit fault
    Code 75- System voltage low charging system problem

    I think the first two have to do with the distributor and if so, what gives? The one I put in was a brand spanking new AcDelco unit so why would it be throwin codes? I think the last one is caused by my stereo and stock alternator, no biggie. Thx
  2. HarryH3

    HarryH3 1 ton status Author

    May 31, 2000
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    Georgetown, TX
    Before you go nuts looking for ghosts, reset the codes and drive around without the stereo for a while. The code 75 means that the voltage is getting low enough to start freaking out the ECM. You may find that the other codes are just byproducts of the low voltage. /forums/images/graemlins/cool.gif
  3. dyeager535

    dyeager535 1 ton status Premium Member

    Dec 13, 2000
    Likes Received:
    Roy WA
    If low voltage is indeed a problem, that is the FIRST thing I'd fix. If you aren't getting enough power, no telling what kind of things the computer will see as being wrong, as some signals are voltage referenced.

    Assuming this is an '89 or newer, VSS buffer is behind the speedometer, but runs both to the ECM and cruise, if present.

    The ESC module is another part of the ignition system. (Electronic Spark Control)

    Again though, low voltage is the FIRST thing that needs to be fixed, then clear the codes, and check again. May or may not solve the other problems, but makes much more sense to fix known problems first.

    Just because a code pops up doesn't mean the component is faulty, it could just as easily be a wiring issue, or even something totally "unrelated", like getting a MAP sensor code, but having a vacuum leak in reality. (IE ECM sees a sensor constantly out of "normal" range, so assumes the sensor is bad, when in reality something else is bad causing the sensor to read what is actually going on, but that is outside of the ECM's "normal" parameters)

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