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Home >> Pontiac >> 2002 >> Aztek AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Engine Sensors & Switches >> Manifold Absolute Pressure Sensor (3.4L) >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS or SELF-DIAGNOSTICS - 3.4L MONTANA, SILHOUETTE & VENTURE article. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Install a scan tool. Turn ON the ignition, with the engine OFF. With the scan tool observe the MAP sensor pressure. Compare this value to a value observed in a known good vehicle. Is the difference between the two vehicles less than 3 kPa? If yes, go to next step. If no, go to step  7.
  3. Observe the MAP sensor pressure on the scan tool. Start the engine. Does the MAP sensor value change? If yes, go to next step. If no, go to step  7.
  4. Turn OFF the ignition. Remove the MAP sensor from the engine vacuum source. Leave the MAP sensor connected to the engine harness. Connect a Vacuum Pump (J 23738-A) to MAP sensor. Turn ON the ignition, with the engine OFF. Observe the MAP sensor pressure as you SLOWLY apply vacuum 1 in. Hg at a time. Each one inch of vacuum should result in a 3 to 4 kPa drop in the MAP sensor pressure. Does the scan tool indicate that the MAP sensor is operating normally? If yes, go to next step. If no, go to step  15.
  5. Observe the MAP sensor pressure on the scan tool with 20 in. Hg of vacuum applied to the sensor. Is the pressure less than 34 kPa? If yes, go to next step. If no, go to step  7.
  6. Disconnect the MAP sensor from the J 23738-A. The MAP sensor pressure should return to the value observed in step  2. Does the MAP sensor pressure return to the value observed earlier? If yes, system is okay. If no, go to step  15.
  7. Turn OFF the ignition. Disconnect the MAP sensor from the engine harness. Turn ON the ignition, with the engine OFF. Observe the MAP sensor VOLTAGE display on the scan tool. Is the voltage more than 0.1 V? If yes, go to step  11. If no, go to next step.
  8. Connect a test light to a good ground. Probe the 5-volt reference circuit of the MAP sensor with the test light. Perform a voltage drop test across the test light with a DVOM. Does the voltage measure more than 4.4 V? If yes, go to next step. If no, go to step  12.
  9. Jumper the MAP sensor 5-volt reference circuit to the MAP sensor signal circuit using a fused jumper wire. Does the scan tool indicate that the MAP sensor voltage is near 5 V? If yes, go to next step. If no, go to step  13.
  10. Remove the jumper. Disconnect the electrical connector of the Engine Coolant Temperature (ECT) sensor. Probe the MAP sensor low reference circuit with a test light connected to battery positive voltage. Does the test light illuminate? If yes, go to step  15. If no, go to step  14.
  11. Test the signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  19. If no, go to step  17.
  12. Test the 5-volt reference circuit of the MAP sensor for high resistance or an open. Did you find and correct the condition? If yes, go to step  19. If no, go to step  17.
  13. Test the signal circuit for the following conditions:
    • High resistance.
    • An open.
    • A short to ground.

    Did you find and correct the condition? If yes, go to step  19. If no, go to step  17.

  14. Test the MAP sensor low reference circuit for high resistance or an open. Did you find and correct the condition? If yes, go to step  19. If no, go to step  17.
  15. Inspect the MAP sensor connector for poor connection or terminal contact. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  16. Replace the MAP sensor. After repairs, go to step  19.
  17. Inspect the PCM for poor connection or terminal contact. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  18. Replace PCM. Program replacement PCM. See POWERTRAIN CONTROL MODULE under PROGRAMMING in appropriate SELF-DIAGNOSTICS article. After repairs, go to next step.
  19. Use the scan tool in order to clear the DTCs that may have set. Turn OFF the ignition for 30 seconds. Start the engine. Did you correct the condition? If yes, system is okay. If no, go to step  2.
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