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Home >> Chevrolet >> 1998 >> Tracker 2D Utility, RWD, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1408: Manifold Absolute Pressure (Map) Sensor Circuit >> Diagnostic Test

Diagnostic Test

  1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK  .
  2. Start engine. Warm engine to normal operating temperature. Using a voltmeter, backprobe MAP sensor input signal (Brown/Yellow wire) at PCM harness connector. If 0.2-4.6 volts exists, go to next step. If 0.2-4.6 volts does not exist, go to step 4).
  3. Turn ignition switch to RUN position. Use scan tool to clear information function. Operate vehicle within freeze frame conditions. If DTC P1408 is set, go to next step. If DTC P1408 is not set, check the following and repair as necessary:
    • Vacuum line for damage or misrouted.
    • Connection at PCM and MAP sensor.
    • Damaged wiring harness.
  4. Turn ignition switch to LOCK position. Disconnect MAP sensor harness connector. Turn ignition switch to RUN position. Measure MAP sensor reference voltage (Gray/Red wire) at MAP sensor harness connector. If 5 volts exists, go to next step. If 5 volts does not exist, go to step 8).
  5. Using a test light connected to battery voltage, probe MAP sensor ground circuit (Brown wire) at MAP sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 9).
  6. Check MAP sensor input signal circuit for open, between PCM and MAP sensor harness connectors. If open does not exist, go to next step. If open exists, repair as necessary and go to step 12).
  7. Turn ignition switch to LOCK position. Connect MAP sensor harness connector. Turn ignition switch to RUN position. Using a voltmeter, backprobe MAP sensor input signal circuit (Brown/Yellow wire) at PCM harness connector. Apply a small amount of vacuum to pressure passage at MAP sensor while observing voltmeter. If voltage does not drop, go to step 10). If voltage drops, go to step 11).
  8. Check MAP sensor reference voltage circuit (Gray/Red wire) for open or short, between PCM and MAP sensor harness connectors. If open or short does not exist, go to step 11). If open or short exists, repair as necessary and go to step 12).
  9. Check MAP sensor ground circuit (Brown wire) for open, between PCM and MAP sensor harness connectors. If open does not exist, go to step 11). If open exists, repair as necessary and go to step 12).
  10. Replace MAP sensor and go to step 12).
  11. Replace PCM and go to next step.
  12. Test drive vehicle under conditions that set the DTC. Check for other DTCs. If DTCs were retrieved, perform appropriate DTC test. If no DTCs were retrieved, system is okay at this time.
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