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 P0100: Mass Air Flow (MAF) Sensor Circuit

DTC P0101: Mass Air Flow (MAF) Sensor Performance

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

P0031, P0037, P0100, P0458

P0100

P0100

--

P0100

MAF Sensor Signal

P0100

P0100

P0100

P0100

P0101, P0102, P0103

Ground

--

P0100

P0100

--

P0100

Typical Scan Tool Data

MAF Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Engine Running

Parameter Normal Range: 1,700-12,500 Hz

Ignition 1 Voltage

65,535 Hz

65,535 Hz

--

MAF Sensor Signal

65,535 Hz

65,535 Hz

65,535 Hz

Ground

--

65,535 Hz

--

Circuit/System Description

The mass air flow (MAF) sensor is integrated with the intake air temperature (IAT) sensor. The MAF sensor is an air flow meter that measures the amount of air entering the engine. The engine control module (ECM) uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle condition. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF/IAT sensor has the following circuits:

    • An ignition 1 voltage circuit
    • A ground circuit
    • A MAF sensor signal circuit
    • An IAT sensor signal circuit
    • A low reference circuit

The ECM applies 5 volts to the MAF sensor on the MAF sensor signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies in a range depending on engine coolant temperature (ECT) of near 1,700 Hertz at idle to near 12,500 Hertz at maximum engine load.

Conditions for Running the DTC

P0100

    • The engine is running.
    • The engine speed is greater than 300 RPM.
    • The ignition 1 voltage signal is greater than 10.5 volts.
    • The above conditions are met for greater than 1 second.
    • This DTC runs continuously within the enabling conditions.

P0101

    • DTCs P0010, P0011, P0013, P0014, P0096, P0097, P0098, P0099, P0100, P0102, P0103, P0106, P0107, P0108, P0121, P0122, P0123, P0221, P0222, P0223, P0236, P0237, P0238, P0335, P0336, P2088, P2089, P2090, P2091, P2176, P2227, P2228, P2229 are not set.
    • The engine is running.
    • The ECM has counted greater than 150 crankshaft revolutions since engine start.
    • The engine coolant temperature (ECT) is greater than 10°C (50°F).
    • The ignition 1 voltage signal is greater than 10.5 volts.
    • The change in the throttle position (TP) is less than 2 percent.
    • The turbocharger bypass valve is Closed.
    • The above conditions are met for greater than 1 second.
        AND
    • Long term cruise fuel trim needs to be active and stable.
    • This DTC runs continuously within the enabling conditions.

P0102

    • The engine is running.
    • The engine speed is greater than 300 RPM.
    • The ignition 1 voltage signal is greater than 10.5 volts.
    • The above conditions are met for greater than 1 second.
    • This DTC runs continuously within the enabling conditions.

P0103

    • The engine is running.
    • The engine speed is greater than 300 RPM.
    • The ignition 1 voltage signal is greater than 10.5 volts.
    • The above conditions are met for greater than 1 second.
    • This DTC runs continuously within the enabling conditions.

Conditions for Setting the DTC

P0100

The ECM detects that the MAF Sensor parameter is equal to 0 Hz for greater than 0.5 second.

P0101

    • The ECM detects that the measured MAF is not within range of a modeled airflow based on the throttle angle and engine speed.
        AND
    • The ECM detects a significant error in the long term fuel trim at cruising speed adaption value.
        AND
    • The ECM detects that the MAF Sensor parameter is not within range of a calculated model that is derived from manifold absolute pressure (MAP) and fuel trim.

P0102

The ECM detects that the MAF Sensor parameter is less than 1035 Hz for greater than 0.5 second.

P0103

The ECM detects that the MAF Sensor parameter is greater than 15,152 Hz for greater than 0.5 second.

Action Taken When the DTC Sets

    • DTC P0100, P0101, P0102, P0103 are Type B DTCs.
    • The ECM will disable boost control and limit the system to mechanical boost only, resulting in a substantial decrease in engine power.

Conditions for Clearing the MIL/DTC

DTC P0100, P0101, P0102, P0103 are Type B DTCs.

Diagnostic Aids

    • If the turbocharger induction hoses become loose or are removed, either at the turbocharger, or the charge air cooler, inlet or outlet, this condition will cause a DTC P0101 to set. As a result, there will be a noticeable decrease in engine power due to the boost control being disabled.
    • A steady or intermittent high resistance of 15 ohms or greater on the ignition 1 voltage circuit will cause the MAF sensor signal to be increased by as much as 60 g/s. A slightly greater resistance can cause the signal to cease. To pinpoint this condition perform a voltage drop test on the circuit.
    • The MAF sensor ignition 1 voltage circuit is spliced to other components of the vehicle. A short to ground or a shorted component will affect all of the devices on this circuit.
    • Any type of contamination on the MAF sensor heating elements will degrade the proper operation of the sensor. Certain types of contaminants act as a heat insulator, which will impair the response of the sensor to airflow changes. Water or snow can create the opposite effect, and cause the signal to increase rapidly.
    • Depending on the current ambient temperature, and the vehicle operating conditions, a MAF sensor signal circuit that is shorted to the IAT signal circuit will increase or decrease the MAF sensor signal that is interpreted by the ECM.
    • Any type of MAF sensor circuit fault may cause the ECM to report to the scan tool a value of 65,535 Hz and 655.35 g/s.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views

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

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls
    •  Scan Tool Snapshot Procedure

Special Tools

J 38522 Variable Signal Generator

Circuit/System Verification

    • Verify the integrity of the entire air induction system, including all turbocharger components, by inspecting for the following conditions:
       - Any damaged components
       - Loose or improper installation
       - An air flow restriction
       - Any vacuum leak
       - A turbocharged air leak
       - Water intrusion
       - In cold climates, inspect for any snow or ice buildup
    • Engine idling, observe the scan tool MAF Sensor parameter. The reading should be between 1,700-3,200 Hz depending on the engine coolant temperature (ECT).
    • A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 2-6 g/s at idle to greater than 200 g/s at the time of the 1-2 shift.
    • Verify that any electrical aftermarket devices are properly connected and grounded. Refer to Checking Aftermarket Accessories.

Circuit/System Testing

  1. Ignition OFF, disconnect the MAF/IAT harness connector at the MAF/IAT sensor.
  2. Ignition OFF for 90 seconds, test for less than 5.0 ohms of resistance between the ground circuit terminal B and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C and ground.
  5. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  6. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal A and ground.
  7. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
    If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  8. Connect the J 38522 to the vehicle. Refer to Component Testing for instructions.

Component Testing

To determine if the ECM can properly process the MAF sensor frequency signal, connect the J 38522 to the vehicle as follows:

  1. Turn OFF the ignition.
  2. Connect the battery voltage supply, and ground the black lead.
  3. Connect the red lead to the signal circuit of the MAF sensor.
  4. Set the Duty Cycle switch to Normal.
  5. Set the Frequency switch to 5 K.
  6. Set the Signal switch to 5 V.
  7. Start the engine.
  8. Observe the MAF Sensor parameter for the correct range of 4,950-5,025 Hz.
  9. If the MAF Sensor parameter is not within the specified range, replace the ECM.
    If the MAF Sensor parameter is within the specified range, replace the MAF sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Mass Airflow Sensor Replacement
    •  Control Module References for ECM replacement, setup, and programming