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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 370 (Engine Control System - Self-Diagnostics - 4.2L) >> Diagnostic Tests >> DTC P0340: Camshaft Position Sensor "A" Circuit (Bank 1) >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Oldsmobile Bravada, 2003 GMC Envoy XL, 2003 GMC Envoy, and 2003 Chevrolet TrailBlazer. 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. Connect scan tool. Start and idle engine. Use scan tool in order to monitor the CMP active counter. Does scan tool indicate the CMP active counter is incrementing? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records data. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions For Running DTC or as close to the Freeze Frame/Failure Records data that you observe. See CONDITIONS FOR RUNNING DTC . Does the DTC reset? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect the CMP sensor. Turn ignition on, with engine off. Probe the 12-volt reference circuit with a test light that is connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  7.
  5. Turn ignition off. Jumper the CMP circuits from the CMP sensor to the CMP sensor harness connector. Turn ignition on, with engine off. Measure the voltage drop from the low reference circuit of the CMP sensor to a good ground with a DVOM. Is the voltage more than 0.2 volt? If yes, go to step  8. If no, go to next step.
  6. Leave the jumper wires installed. Remove the jumper wire from the CMP sensor signal circuit on the PCM side. Start the engine. Measure the duty cycle from the CMP sensor signal circuit on the sensor side and to a good ground with a DVOM. Is the duty cycle within 40-50 percent? If yes, go to step  9. If no, go to step  10.
  7. Test the 12-volt reference circuit for an open, high resistance or a short to ground. Did you find and correct the condition? If yes, go to step  15. If no, go to step  11.
  8. Test the low reference circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  15. If no, go to step  11.
  9. Test the signal circuit for an open, short to ground or a short to voltage. Did you find and correct the condition? If yes, go to step  15. If no, go to step  11.
  10. Test for an intermittent and for a poor connection at the CMP sensor. Did you find and correct the condition? If yes, go to step  15. If no, go to step  12.
  11. Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  15. If no, go to step  14.
  12. Remove the CMP sensor. Visually inspect the CMP sensor for physical damage, loose or improper installation. Did you find and correct the condition? If yes, go to step  15. If no, go to next step.
  13. Replace CMP sensor. See REMOVAL & INSTALLATION - BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article. After replacing sensor, go to step  16.
  14. Replace PCM. See REMOVAL & INSTALLATION - BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  15. Clear the DTCs with scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions For Running DTC. See 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 scan tool. Does 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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