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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 239 (ENGINE CONTROLS SELF-DIAGNOSTICS - 3.1L ENGINE)DIAGNOSTIC TESTSDTC P0336: CRANKSHAFT POSITION SENSOR PERFORMANCEDIAGNOSTIC PROCEDURE
1999 GMC Forward Control 5.7 R, Automatic

Diagnostic Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Start the engine. Observe the 24X parameter using a scan tool. Does 24X RPM vary with engine speed up to approximately 1600 RPM? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running Test or as close to the Freeze Frame/Failure Records data observed. See CONDITIONS FOR RUNNING TEST . Does the DTC fail this ignition? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
    4. NOTE: A short to ground on the Camshaft Position (CMP) or Crankshaft Position (CKP) sensor 12-volt reference circuit can cause DTC P0327 to set. Test this circuit for a short to ground before proceeding with this test.
  4. Turn ignition switch to OFF position. Disconnect the CKP sensor "A" connector. Turn ignition switch to RUN position, engine OFF. Measure the voltage from the CKP sensor "A" 12-volt reference circuit to a good ground using the DMM. Does the voltage measure near battery voltage? If yes, go to step  6. If no, go to next step.
  5. Test the CKP sensor "A" 12-volt reference circuit for the following conditions:
    • An open.
    • A short to ground.
    • High resistance.

    Did you find and correct the condition? If yes, go to step  16. If no, go to step  12.

  6. Connect a test light to positive battery voltage. Touch the CKP sensor "A" low reference circuit. Does test light illuminate? If yes, go to step  8. If no, go to next step.
  7. Test the CKP sensor "A" low reference circuit for an open or for high resistance. Did you find and correct the condition? If yes, go to step  16. If no, go to next step.
  8. Observe the 24X RPM using a scan tool. Connect a 5-amp fused jumper wire to battery positive voltage, momentarily touch the medium resolution engine speed signal circuit 5 times for a duration of one second each. Does 24X RPM change each time the signal circuit is touched? If yes, go to step  13. If no, go to next step.
  9. Did the fuse in the jumper wire open? If yes, go to step  11. If no, go to next step.
  10. Test the CKP sensor "A" medium resolution engine speed signal circuit for the following conditions:
    • An open.
    • A short to voltage.
    • High resistance.

    Did you find and correct the condition? If yes, go to step  16. If no, go to step  12.

  11. Test the medium resolution engine speed signal circuit of the CKP sensor "A" for a short to ground. Did you find and correct the condition? If yes, go to step  16. If no, go to step  12.
  12. Test for an intermittent or for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  16. If no, go to step  14.
  13. Test for an intermittent or for a poor connection at the 24X CKP sensor. Did you find and correct the condition? If yes, go to step  16. If no, go to step  15.
  14. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to step  16.
  15. Replace CKP sensor "A". After repair, go to next step.
  16. Using scan tool, clear the DTCs. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running Test. See CONDITIONS FOR RUNNING TEST . Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  17. Using the scan tool, observe the stored information in CAPTURE INFO. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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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.