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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 31 (ENGINE CONTROLS - 6.6L - DIAGNOSIS (DTCs P0402-P2636)) >> DTC P0642 or P0643 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.

  1. Turn OFF the ignition for 30 seconds or until the ECM powers down.
  2. Disconnect the camshaft position (CMP) sensor.
  3. Turn ON the ignition, with engine OFF and measure the voltage from the 5-volt reference circuit of the CMP sensor to a good ground with a DMM.
    • If the voltage measures 4.7-5.2 volts, replace the camshaft position sensor.
  4. With the DMM still connected to the 5-volt reference circuit, disconnect the crankshaft position (CKP) sensor.
    • If the voltage measures 4.7-5.2 volts, replace the CKP sensor.
  5. Test the 5-volt reference 1 circuits for a short to ground or a short to voltage.
    • If no problem was found in the 5-volt reference circuit, replace the ECM.
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