GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0102: Mass Air Flow (MAF) Sensor Circuit Low Frequency

DTC P0103: Mass Air Flow (MAF) Sensor Circuit High Frequency

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

Ignition 1 Voltage

P0102

P0102

P0102

--

P0101

5 Volt Reference

P0102

P0102

P0102

P0103

P0101

MAF Sensor Signal

P0102

P0102

P0102

P0103

P0101

Low Reference

--

P0103

P0103

--

P0101

Circuit/System Description

The mass air flow (MAF) sensor is located in the air intake duct. The MAF sensor is an airflow meter that measures the amount of air that enters the engine. The MAF sensor uses a hot film that is cooled by air flowing past the sensing film as air enters the engine. The amount of cooling is proportional to the amount of the air flow. As the air flow increases, more current is required in order to maintain the hot film at a constant temperature. The engine control module (ECM) uses the MAF sensor in order to provide the correct fuel delivery for all operating conditions.

Conditions for Running the DTC

    • Before the ECM can report DTC P0102, or P0103 failed, DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0336, and P0338 must run and pass.
    • The engine is operating.
    • The ignition voltage is greater than 7.5 volts.
    • DTCs P0102 and P0103 run continuously once the above conditions are met for 3 seconds.

Conditions for Setting the DTC

P0102

    • The ECM detects that the MAF sensor signal is less than -12 grams per second.
    • The condition exists for 4 seconds or for a cumulative of 50 seconds.

P0103

    • The ECM detects that the MAF sensor signal is greater than 294 grams per second.
    • The condition exists for 4 seconds or for a cumulative of 50 seconds.

Action Taken When the DTC Sets

DTCs P0102, and P0103 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0102, and P0103 are Type B DTCs.

Diagnostic Aids

The following table illustrates the ECM connector locations:

ECM Connector Location

X2

X1

Front of Vehicle

    • Inspect the harness of the MAF sensor to verify that it is not routed too close to the following components:
       - The secondary ignition wires or coils
       - Any solenoids
       - Any relays
       - Any motors
    • Inspect the hydro-carbon (HC) filter in the air cleaner assembly for ruptures that would leak charcoal into the air intake, contaminating the sensing element.
    • Inspect for any contamination, water intrusion, or debris on the sensing elements of the MAF sensor. If debris is present, clean the sensor. If the sensor cannot be cleaned, replace the sensor.
    • A high resistance may cause a driveability concern before this DTC sets.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Air Intake System Description

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Engine idling for 1 minute, observe the scan tool DTC information. DTCs P0102, and P0103 should not set.
  2. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
  2. Remove the fuse that supplies B+ to circuit terminal X2-36 of the engine control module (ECM).
  3. Test for less than 5 ohms between the low reference circuit terminal 3 and ground.
  4. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  5. Install the fuse that supplies B+ to circuit terminal X2-36 of the ECM.
  6. Notice: Do NOT use the low reference circuit in the component harness connector for this test. Damage to the control module may occur due to excessive current draw.

  7. Ignition ON, load test for B+ between the ignition voltage circuit terminal 2 and ground.
  8. If less than the specified range, repair the ignition voltage circuit for an open/high resistance.

    Important: The engine control module (ECM) for this engine is not equipped with 5-volt reference DTCs. The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors.

  9. Test for 4.8-5.2 volts between the 5 volt reference circuit terminal 4 and the low reference circuit terminal 3 .
  10. If less than the specified range, test the 5 volt reference circuit for an open or for a short to ground. If the circuit/connections test normal, replace the ECM.
    If greater than the specified range, test the 5 volt reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.
  11. Test for greater than 80 mA between the 5 volt reference circuit terminal 4 and the low reference circuit terminal 3.
  12. If less than the specified range, test the 5 volt reference circuit for a high resistance. If the circuit/connections test normal, replace the ECM.
  13. Install a 3A fused jumper wire between the 5 volt reference circuit terminal 4 and the signal circuit terminal 5. Verify the scan tool MAF sensor voltage parameter is between 4.8-5.2 volts.
  14. If not within the specified range, test the signal circuit for a high resistance. If the circuit/connections test normal, replace the ECM.
  15. If all circuits/connections test normal, replace the MAF sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Mass Airflow Sensor/Intake Air Temperature Sensor Replacement
    •  Control Module References for engine control module replacement, setup, and programming