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Home >> Chevrolet >> 2002 >> Cutaway 6.5 F >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics - 6.5L >> Diagnostic Tests >> DTC P0370: Timing Reference High Resolution >> Diagnostic Procedures

Diagnostic Procedures

  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Turn OFF the ignition. Disconnect the optical/fuel temperature sensor electrical connector. Turn ON the ignition, with the engine OFF. Use a Digital Multimeter (DMM) in order to measure the voltage between the optical sensor 5-volt reference circuit at the harness connector and chassis ground. Does the voltage measure 4.8-5.2 V? If yes, go to next step. If no, go to step  6 .
  3. Verify the optical/fuel temperature sensor electrical connector is still disconnected. Probe the sensor ground circuit with an Unpowered Test Light (J 34142-B) connected to battery voltage at the harness connector. Does the test lamp illuminate? If yes, go to next step. If no, go to step  7 .
  4. Reconnect the optical/fuel temperature sensor electrical connector. Start the engine. Operate the engine close to the conditions saved in the Freeze Frame/Failure Records. Use the scan tool in order to select DTC and the Specific DTC function. Enter the DTC number that was set. Does the scan tool display the term Last Test Failed? If yes, go to next step. If no, see DIAGNOSTIC AIDS  .
    5. NOTE: The scan tool must display Last Test Failed (under DTC, Specific). This ensures the fault is active while performing this test.
  5. Maintain the engine speed at the point of failure, per the conditions saved in the Freeze Frame/Failure Records. With the DMM on the Hertz (Hz) scale, backprobe the high resolution signal circuit at the PCM. See RPM VS HERTZ FOR HIGH RESOLUTION SIGNAL  table, does the Hertz reading in the table correspond (plus or minus 100 Hz) with the Hertz reading on the DMM at the designated RPM? If yes, go to step  16 . If no, go to step  9 .
  6. Turn OFF the ignition. Disconnect the PCM, and check the optical sensor 5-volt reference circuit for the following:
    • An open.
    • A short to ground.
    • A short to the sensor ground circuit.

    If the optical sensor 5-volt reference circuit is open or shorted to ground, repair the circuit as necessary. Did you perform a repair? If yes, go to step  19 . If no, go to step  8 .

  7. Check for an open or a poor sensor ground terminal connection at the PCM. If a problem is found, repair as necessary. Did you perform a repair? If yes, go to step  19 . If no, go to step  18 .
  8. Check the optical sensor 5-volt reference circuit for a poor connection at the PCM and replace the terminal if necessary. Did you perform a repair? If yes, go to step  19 . If no, go to step  18 .
  9. Disconnect the optical/fuel temperature sensor electrical connector. Turn ON the ignition, with the engine OFF. With a DMM connected to ground, probe the high resolution signal circuit at the harness connector. Does the voltage measure 4.8-5.2 V? If yes, go to step  13 . If no, go to next step.
  10. Does the voltage measure more than 4.8-5.2 V? If yes, go to next step. If no, go to step  12 .
  11. Repair the short to battery/ignition voltage on the high resolution signal circuit. After repairs, go to step  19 .
  12. Turn OFF the ignition. Disconnect the PCM, and check the high resolution signal circuit for any of the following conditions:
    • An open
    • A short to ground
    • A short to the sensor ground circuit

    If a problem is found, repair the problem as necessary. Did you perform a repair? If yes, go to step  19 . If no, go to step  16 .

  13. With a DMM set to the mA scale, measure the current between the high resolution signal circuit and the ground circuit at the optical/fuel temperature sensor electrical connector. Does the current measure less than 25 mA? If yes, go to step  15 . If no, go to next step.
  14. Repair the short to reference voltage on the high resolution signal circuit. After repairs, go to step  19 .
  15. Check for a poor connection at the injection pump. If a problem is found, repair the problem as necessary. Did you perform a repair? If yes, go to step  19 . If no, go to step  17 .
  16. Turn OFF the ignition. Disconnect the PCM, and check the high resolution signal circuit for a poor connection at the PCM. If a problem is found, repair the problem as necessary. Did you perform a repair? If yes, go to step  19 . If no, go to step  18 .
    17. NOTE: The new injection pump must be timed. See appropriate ON-VEHICLE ADJUSTMENTS article.
  17. Replace the fuel injection pump. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  19 .
  18. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  19. Using the scan tool, clear the DTCs. Start engine and idle the engine at the normal operating temperature. Select DTC and the Specific DTC function. Enter the DTC number that was set. Operate the vehicle within the Conditions for Setting DTC until the scan tool indicates the diagnostic ran. Does the scan tool indicate the diagnostic passed? If yes, go to next step. If no, go to step  2 .
  20. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, system is okay.
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