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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 155 (Engine Controls Self-Diagnostics - 5.7L - Bi-Fuel) >> Diagnostic Tests >> DTC P0103: MAF Sensor Circuit - High Frequency >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Start and idle the engine. Using the scan tool, establish communication with the PCM. Observe the MAF sensor data parameter. Does the MAF sensor data parameter indicate frequency more than 10.39 kHz? If yes, go to step  5 . If no, go to next step.
  3. Using the scan tool, establish communication with the Alternative Fuels ECM. Observe the MAF sensor data parameter with the engine idling. Does the MAF sensor data parameter indicate airflow more than 20 gms/sec? If yes, go to step  10 . If no, go to next step.
  4. The fault is not present. Are any DTCs stored that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, problem is intermittent. See INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  5. Disconnect the MAF sensor connector. Observe the MAF sensor data parameter with the engine idling. Does the MAF sensor data parameter indicate frequency more than 0 Hz? If yes, go to next step. If no, go to step  8 .
  6. Turn OFF the ignition. Disconnect the Alternative Fuels ECM connectors. Start and idle the engine. Observe the MAF sensor data parameter with the engine idling. Does the MAF sensor data parameter indicate frequency more than 0 Hz? If yes, go to next step. If no, go to step  10 .
  7. A high frequency signal may be induced on the MAF signal circuit by sources other than the MAF sensor. Inspect the vehicle for the following conditions:
    • A MAF signal circuit routed near secondary ignition components.
    • A MAF signal circuit routed near high current components such as motors, relays, etc.
    • High power transceivers operating in or near the vehicle.

    Route the wiring harness correctly or remove the source of high frequency. Was an induced high frequency source found and corrected? If yes, go to step  11 . If no, go to step  9 .

  8. Replace the MAF Sensor. See MASS AIR FLOW SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE. After repairs, go to step  11 .
    9. NOTE: The following Control Module replacement procedures must all be completed before attempting to operate the vehicle.
  9. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CHEVY EXPRESS & SAVANA - GASOLINE. Program (flash) PCM with correct vehicle software and calibration. See POWERTRAIN CONTROL MODULE REPROGRAMMING  under PROGRAMMING. To perform CKP variation learn procedure, a switchover to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switchover. Perform CKP system variation learn procedure. See CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE  under PROGRAMMING. After performing repairs and procedures, go to step  11 .
  10. Replace AF ECM. See ALTERNATE FUEL ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL. Program (flash) AF ECM with correct vehicle software and calibration. See ALTERNATE FUEL ENGINE CONTROL MODULE  under PROGRAMMING. After performing repairs and procedures, go to next step.
  11. Using a scan tool, clear the DTC information from BOTH Control modules. Operate the vehicle under the Conditions For Running DTC. Using the scan tool parameter DTC STATUS, ensure that this DTC runs. Did this DTC run and pass? If yes, system is okay. If no, go to step  2 .
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