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Diagnostic Procedures

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  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? If yes, go to next step. If no, go to step  5.
  3. Monitor the Diagnostic Trouble Code (DTC) Information with the scan tool. Does the scan tool display any other DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  4. Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running DTC or as close to the Freeze Frame/Failure Records data that you observed. See CONDITIONS FOR RUNNING DTC . Does the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
    5. NOTE: The Altitude vs. Barometric Pressure table indicates a pressure range for a given altitude under normal weather conditions. Weather conditions consisting of very low or very high barometric pressure and/or temperature may cause a reading to be slightly out of range.
  5. Turn ignition on, with engine off. Observe the MAP sensor kPa parameter with a scan tool. The MAP sensor pressure should be within the specified range for your altitude. Refer to Altitude vs Barometric Pressure in SENSOR OPERATING RANGE CHARTS - TRUCKS article. Is the MAP sensor pressure within the specified range as indicated on the chart? If yes, go to next step. If no, see DTC P0106: MAP SYSTEM PERFORMANCE .
  6. Start engine. Turn OFF all accessories. Allow engine to reach operating temperature. Observe the MAP sensor parameter with scan tool. Is MAP sensor parameter within 0.8-2.0 volts? If yes, go to next step. If no, see DTC P0106: MAP SYSTEM PERFORMANCE .
  7. Idle the engine. Observe the MAP sensor parameter with a scan tool. Increase engine speed slowly to 3000 RPM and then back to idle. Does the MAP sensor parameter change smoothly and gradually through the specified range of the test? If yes, go to next step. If no, see DTC P0106: MAP SYSTEM PERFORMANCE .
  8. Turn ignition off for 30 seconds. Turn ignition on, with engine off. Observe the TP sensor parameter at closed throttle with a scan tool. Depress the accelerator pedal completely. Observe the TP sensor parameter at wide-open throttle with a scan tool. Does the TP sensor parameter change from 0-100 percent? If yes, go to step  9. If no, go to DTC P0121: TP SENSOR PERFORMANCE .
  9. Turn ignition off. Inspect for a restricted or collapsed air intake duct, misaligned air intake duct, dirty or deteriorating air filter element, objects blocking air inlet screen of the MAF sensor, any contamination or debris on the sensing elements of the MAF sensor, water intrusion in the induction system, vacuum leak downstream of the MAF sensor, or any type of restriction in the exhaust system. Did you find and correct the condition? If yes, go to step  14. If no, go to next step.
  10. Disconnect the harness connector of the MAF sensor. Turn ignition on, with engine off. Connect a test light between the ignition 1 voltage circuit of the MAF sensor and a good ground. Connect a DVOM to the probe of the test light and a good ground. Is the voltage less than battery voltage? If yes, go to step  12. If no, go to next step.
  11. Test for an intermittent and for a poor connection at the MAF sensor. Did you find and correct the condition? If yes, go to step  14. If no, go to next step.
  12. Repair the high resistance in the ignition 1 voltage circuit of the MAF sensor. After repairs, go to step  14.
  13. Replace MAF sensor. See appropriate REMOVAL & INSTALLATION article. After repairs, go to next step.
  14. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate the 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  3.
  15. 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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