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 P0101: Mass Air Flow (MAF) Sensor Performance

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

Ignition 1 Voltage

P0100, P0102

P0100, P0102

P0100, P0102

--

P0101

MAF Sensor Signal High

P0100, P0102

P0100, P0102

P0100, P0102

P0100, P0103

P0101

MAF Sensor Signal Low

--

P0100, P0103

P0100, P0103

--

P0101

Typical Scan Tool Data

MAF Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Engine idling in Closed Loop.

Parameter Normal Range: MAF Sensor 1.5-5.0 g/s

Ignition 1 Voltage

0.40 g/s

0.40 g/s

--

MAF Sensor Signal High

0.40 g/s

0.40 g/s

228 g/s

MAF Sensor Signal Low

228 g/s

228 g/s

*

* Internal PCM damage may occur if the circuit is shorted to B+.

Circuit/System Description

The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The control module uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. The MAF sensor is a hot wire design. A platinum hot wire and a thermistor are located in the intake air bypass passage of the MAF sensor housing. The temperature of the platinum hot wire is affected by exposure to air flow and by exposure to air temperature. The platinum hot wire is maintained at a set temperature by controlling the current flow through the wire. The MAF sensor converts the changes in current flow to a voltage signal. The voltage signal from the MAF sensor enables the PCM to detect changes in air density and changes in air volume.

Conditions for Running the DTC

    • DTCs P0100, P0102, P0103, P0115, P0117, P0118, P0120 P0122, P0123, P0125, P0335, P0340, P0341, P2135 are not set.
    • The engine is running.
    • The battery voltage is greater than 10.5 volts.
    • The engine coolant temperature (ECT) is greater than 75°C (167°F).
    • DTC P0101 runs continuously when the above conditions are met.

Conditions for Setting the DTC

    • The engine speed is 2,000 RPM or less.
    • The throttle valve is closed.
    • The MAF sensor output is greater than 2.2 volts.
    • The condition is present for greater than 10 seconds.

OR

    • The engine speed is 300 RPM or more.
    • The throttle position (TP) sensor input is greater than 0.63 volt.
    • The MAF sensor output is less than 0.93 volt.
    • The condition is present for greater than 10 seconds.

Action Taken When the DTC Sets

DTC P0101 is a Type B DTC.

Conditions for Clearing the DTC

DTC P0101 is a Type B DTC.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Powertrain 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

Control Module References for scan tool information

Circuit/System Verification

  1. Engine running for 1 minute, verify the MAF sensor scan tool parameter is between 1.5-5.0 g/s.
  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 you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

  1. Verify the following conditions do not exist:
  2. • Objects blocking the MAF sensor inlet
    • Intake manifold vacuum leaks
    • Throttle body vacuum leaks
    • A faulty, missing, or incorrectly installed positive crankcase ventilation (PCV) valve
    • Vacuum hose splits, kinks, or incorrect connections
    • Excessive coking or carbon deposits of the throttle valve and throttle bore
         ⇒If you find any of the above conditions, repair as necessary.
  3. If all conditions test normal, test or replace the MAF sensor.

Component Testing

  1. Ignition OFF, disconnect the harness connector at the MAF sensor.
  2. Important: This test is valid only when the MAF sensor circuits test normal.

  3. Install 3 jumper wires between the MAF sensor and the harness connector terminal as listed:
  4. • MAF sensor signal low circuit terminal 2
    • MAF sensor signal high circuit terminal 3
    • MAF sensor ignition positive voltage circuit terminal 1
  5. Ignition ON, measure for voltage on the MAF signal circuit when blowing air thru the MAF sensor.
  6. If the signal voltage did not increase with air flow, replace the MAF sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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