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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 71 (Engine Controls Self-Diagnostics - 2.2L CNG) >> Diagnostic Tests >> DTC P0500: VSS Circuit >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Chevrolet Cavalier. 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. Using scan tool, establish communication with the PCM. Inspect for stored powertrain DTCs. Are DTCs DTC P0502 or DTC P0503 stored? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, go to next step.
  3. Observe the AF ECM Freeze Frame and/or Failure records data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame and/or Failure records data that you observed. See CONDITIONS FOR RUNNING DTC  . Does the DTC fail this ignition? If yes, go to step  5 . If no, go to next step.
  4. The fault is not present. See DIAGNOSTIC AIDS  . Are any DTCs stored that have not been diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, refer to INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  5. Turn ignition off. Disconnect the cruise control module electrical connector. Raise and support the vehicle with the drive wheels off the ground. Connect the J-39200 Digital Multimeter (DMM) negative test lead to the VSS input circuit terminal of the cruise control module connector. Connect the J-39200 Digital Multimeter (DMM) positive test lead to battery positive. Start engine and place transmission in Drive. Measure the DC frequency on the VSS input circuit while rotating the drive wheels at 20 MPH. Is the frequency measured greater than 15 Hz? If yes, go to next step. If no, go to step  7 .
  6. Turn ignition off. Disconnect the AF ECM. Connect DMM negative test lead to the VSS input circuit terminal of the ECM connector. Connect DMM positive test lead to battery positive. Start engine and place transmission in Drive. Measure the DC frequency on the VSS input circuit while rotating the drive wheels at 20 MPH. Is the frequency measured greater than 15 Hz? If yes, go to step  8 . If no, go to step  11 .
  7. Test the VSS circuit for an open or shorted condition. Inspect PCM connector terminals for proper contact. Repair the wiring or terminals as necessary. Was a repair necessary? If yes, go to step  12 . If no, go to step  10 .
  8. Inspect the AF ECM connector for proper terminal contact. Repair the terminal as necessary. Was a repair necessary? If yes, go to step  12 . If no, go to next step.
  9. Replace AF ECM. See ALTERNATE FUEL ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECM with correct vehicle software and calibration. See ALTERNATE FUEL ENGINE CONTROL MODULE  under PROGRAMMING. After performing repairs and procedures, go to step  12 .
  10. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See POWERTRAIN CONTROL MODULE REPROGRAMMING  under PROGRAMMING. To perform CKP variation learn procedure, a switchover to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switchover. Perform CKP system variation learn procedure. See CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE  under PROGRAMMING. After performing repairs and procedures, go to step  12 .
  11. Repair the open VSS circuit between the AF ECM and splice. After repairs, go to next step.
  12. Use scan tool in order to clear the DTCs from both control modules. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC  . Does the DTC run and pass? If yes, system is okay, If no, go to step  2 .
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