Diagnostic Aids

Perform this test when instructed during QUICK TEST  or if directed by other test procedures. This test is used to diagnose the cause associated with failure to complete drive cycle mode 1. See OBD II-B DRIVE CYCLE MODES . The following items may be at fault.

• Battery or PCM has been disconnected.
• An OBD-II monitor has failed before completion of drive cycle.
• PCM memory has been erased with a scan tool.
• Fuel System
• Engine Coolant Temperature (ECT) Sensor.
• Intake Air Temperature (IAT) Sensor.
• Mass Airflow (MAF) Sensor.
• Evaporative (EVAP) canister purge solenoid.
• Intake air leak.
• EGR boost sensor.
• Faulty PCM.

1. 1) Check For DTCs  If any trouble codes are present, service as necessary. If no trouble codes are present, go to next step.
2. 2) Check Air Intake System  Check air intake system for air leaks, excessive dirt or other damage. Repair as necessary and perform Drive Cycle Mode 1. If air intake system is okay, go to next step.
3. 3) Check PCV System  Check PCV system for air leaks, excessive dirt or other damage. Repair as necessary and perform Drive Cycle Mode 1. If PCV system is okay, go to next step.
4. 4) Check Sensor Inputs To PCM  Turn ignition off. Connect scan tester. Start engine (drive if necessary) while monitoring the following PIDs:
   • ECT (engine coolant temperature).
   • IAT (intake air temperature).
   • MAF (mass airflow sensor or MC-VAF sensor).
   • O2S-- (all oxygen sensor PIDs).
   • PURGE (evaporative purge solenoid).
   • PRC (fuel pressure regulator control solenoid).
   • VSS (vehicle speed sensor).

   Compare values to the PIN VOLTAGE CHART S article. If PID values are within the expected range, go to next step. If PID values are not within expected range, see test procedures under CIRCUIT TEST Z , for intermittent diagnostic procedure. Repeat Drive Cycle Mode 1. See OBD II-B DRIVE CYCLE MODES .

5. 5) Check EGR Boost Sensor  Check EGR boost sensor. See CIRCUIT TEST HE . Repair EGR boost sensor as necessary repeat Drive Cycle Mode 1. See OBD II-B DRIVE CYCLE MODES . If EGR boost sensor is okay, go to next step.
6. 6) Check Fuel System  Check fuel system for the following concerns:
   • Fuel pressure regulator problem.
   • Fuel injector malfunction.
   • Fuel pump malfunction.
   • Fuel pressure.

   If any of the above require servicing, perform repair as necessary. Repeat Drive Cycle Mode 1. See OBD II-B DRIVE CYCLE MODES . If the above items are okay, replace PCM. Repeat Drive Cycle Mode 1. See OBD II-B DRIVE CYCLE MODES .