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Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  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. Attempt to start the engine. Does the engine start and run? If yes, see DIAGNOSTIC AIDS . If no, go to next step.
  3. Turn OFF the ignition. Disconnect the CMP sensor. Turn ON the ignition, with the engine OFF. Connect a Digital Multimeter (DMM) between the 12-volt reference and the low reference circuit of the CMP sensor. Does the DMM display a reading above 10 V? If yes, go to step  5. If no, go to next step.
  4. Connect a DMM between the 12-volt reference and chassis ground. Does the DMM display a reading above 10 V? If yes, go to step  7. If no, go to step  8.
  5. Connect a DMM between the CMP sensor signal and a good ground. Does the DMM display 0 V? If yes, go to next step. If no, go to step  9.
  6. Turn OFF the ignition. Reconnect the CMP sensor. Disconnect the ECM connector C1. Carefully remove the CMP signal circuit pin from the ECM connector. Reconnect the ECM connector. Connect a DMM between the CMP signal circuit pin at the ECM and a good ground. Crank the engine and measure the DC duty cycle of the CMP signal. Does the DMM display a DC duty cycle of 45-55 percent? If yes, go to step  12. If no, go to step  10.
  7. Test the low reference circuit for an open. Did you find and correct the condition? If yes, go to step  15. If no, go to step  12.
  8. Test the 12-volt reference circuit for an open or a short to ground. Did you find and correct the condition? If yes, go to step  15. If no, go to step  12.
  9. Test the CMP signal circuit for a short to voltage or a short to the 12-volt reference circuit. Did you find and correct the condition? If yes, go to step  15. If no, go to step  14.
  10. Test the CMP signal circuit for an open or a short to ground. Did you find and correct the condition? If yes, go to step  15. If no, go to next step.
  11. Check for poor connections at the CMP sensor. Did you find and correct the condition? If yes, go to step  15. If no, go to step  13.
  12. Check for poor connections at the ECM. Did you find and correct the condition? If yes, go to step  15. If no, go to step  14.
    13. NOTE: Inspect the CMP sensor for physical damage before replacing.
  13. Replace the CMP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  15.
  14. Replace the ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram ECM. See ENGINE CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  15. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  16. 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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