Shut down @ 1400 RPM 08 388

Discussion in 'Peterbilt Forum' started by SilmSalankey, Nov 20, 2022.

  1. SilmSalankey

    SilmSalankey Bobtail Member

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    Nov 20, 2022
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    My 2008 Peterbilt 388 with a Cummins ISX is doing something very strange. When taken to 1400 RPM it shuts down and throws the check engine, stop engine, abs light, and every every other warning sound and light it can throw. If I take my foot off the throttle after a few moments it kicks back on like nothing.

    When it shuts down everything goes, the engine, the gauges, everything.

    So far we have replaced the ECM, rewired the ECM power and ground, and checked a few fuses to no avail.
     
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  3. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    Remove serpentine belt and try. I have seen alternators do this.
     
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  4. SilmSalankey

    SilmSalankey Bobtail Member

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    Nov 20, 2022
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    Couldnyou be more specific?
     
  5. ducnut

    ducnut Road Train Member

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    Yep. As mentioned, an overcharging alternator will throw every control module into a fit, because the high rpm causes the alternator to produce excess voltage. When the alternator voltage exceeds the voltage range the modules expect to see, the modules shut down. It’s a possible sign of a failing regulator, within the alternator.
     
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