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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 78 (ENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - 3.8L)DIAGNOSTIC TESTSDTC P1336: CKP SYSTEM VARIATION NOT LEARNEDDIAGNOSTIC AIDS
1999 GMC Forward Control 5.7 R, Automatic

Diagnostic Aids

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Aids
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The crankshaft position system variation compensating values are stored in the PCM's non-volatile memory after a learn procedure has been performed. If actual crankshaft position variation is not within the crankshaft position system variation compensating values stored in the PCM, DTC P0300 may set.

The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether DTC P1336 is set:

  • An engine replacement.
  • A PCM replacement.
  • A harmonic balancer replacement.
  • A crankshaft replacement.
  • A crankshaft position sensor replacement.
  • Any engine repairs which disturb the crankshaft to crankshaft position sensor relationship.

If the crankshaft position system variation learn procedure cannot be performed successfully, check the following conditions and correct as necessary:

  • A damaged reluctor wheel.
  • Excessive crankshaft runout.
  • A damaged crankshaft.
  • Interference in the signal circuit of the CKP sensor.
  • A coolant temperature that is not within the Condition For Running DTC.
  • The ignition switch is in the on position until the battery is drained.
  • A PCM power disconnect with the ignition on may erase the stored value and set the DTC P1336.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.