GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2006 🢒 RELAY - AWD 🢒 Brakes 🢒 Park Brake 🢒 DTC P0101

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 Descriptor

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

P0102

P0101

P0102

--

P0101, P0103

MAF Sensor Signal

P0102

P0102

P0102

P0102

P0101, P0103

Ground

--

P0102

P0102

--

P0102

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. 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 sensor has the following circuits:

    • An ignition 1 voltage circuit
    • A MAF sensor signal circuit
    • A ground circuit

The control module applies a voltage to the sensor on the signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies within a range of near 2,000 Hertz at idle to near 10,000 Hertz at maximum engine load. The control module uses the following sensor inputs to calculate a predicted MAF value:

    • The barometric pressure (BARO) at key ON
    • The manifold absolute pressure (MAP) sensor
    • The intake air temperature (IAT) sensor
    • The engine coolant temperature (ECT) sensor
    • The throttle position indicated angle
    • The engine speed (RPM)

The control module compares the actual MAF sensor frequency signal to the predicted MAF value. This comparison will determine if the signal is stuck based on a lack of variation, or is too low or too high for a given operating condition. If the control module detects the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value, DTC P0101 sets.

Conditions for Running the DTC
    • DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0128, P0401, P0403, P0404, P0405, P0406, P0442, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P1106, P1107, P1111, P1112, P1114, P1115, or P1404 are not set.
    • The engine is running.
    • The ignition 1 signal is between 9-18 volts.
    • If the ignition 1 signal is less than 11.5 volts, then the MAF must be less than 40 g/s.
    • The throttle position indicated angle is less than or equal to 100 percent.
    • The change in the throttle position indicated angle is less than or equal to 15 percent.
    • The traction control is inactive, if equipped.
    • The exhaust gas recirculation (EGR) flow diagnostic is inactive.
    • The EGR is less than or equal to 100 percent.
    • The EGR DC is less than or equal to 100 percent.
    • The evaporative emission (EVAP) canister purge valve duty cycle is less than or equal to 100 percent.
    • The MAP sensor is less than 80 kPa.
    • The change in the MAP sensor is less than 5 kPa.
    • The above conditions are met for more than 2 seconds.

Conditions for Setting the DTC

The control module detects that the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value for more than 40 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
    • Inspect the harness of the MAF sensor to verify that it is not routed too close to the following components:
       - Any aftermarket accessories--Refer to Checking Aftermarket Accessories .
       - The secondary ignition wires or coils
       - Any solenoids
       - Any relays
       - Any motors
    • A low minimum air rate through the sensor bore at idle or during deceleration may cause this DTC to set. Inspect for the following conditions:
       - Any deposits on the throttle plate or in the throttle bore
       - Any vacuum leak downstream of the MAF sensor
    • Inspect for any contamination or debris on the sensing elements of the MAF sensor.
    • Inspect the air induction system for any water intrusion. Any water that reaches the MAF sensor will skew the sensor and may cause this DTC to set.
    • 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 3-10 g/s at idle to 150 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
    • Inspect for a skewed or stuck ECT sensor.
    • A high resistance of 15 ohms or more on the ignition 1 voltage circuit may cause this DTC to set. A high resistance may cause a driveability concern before this DTC sets.
    • The BARO that is used in order to calculate the predicted mass air flow value is initially based on the MAP sensor at key ON. When the engine is running, the BARO value is continually updated near wide open throttle. A skewed MAP sensor will cause the calculated mass air flow value to be inaccurate and may result in a no start condition. The value shown for the MAP sensor parameter varies with the altitude. With the ignition ON and the engine OFF, 101 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1,000 feet) of altitude.
    • A high resistance on the low reference circuit of the MAP sensor may cause this DTC to set.
    • If the condition is intermittent, refer to Testing for Intermittent Conditions and Poor Connections .

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
    •  Measuring Voltage Drop

Special Tools Required

J 38522 Variable Speed Generator

Circuit/System Testing
  1. Turn ON the ignition, with the engine OFF.
  2. Measure the battery voltage.
  3. Disconnect the MAF sensor.
  4. Connect a test lamp between the MAF sensor ignition 1 voltage circuit and a good ground.
  5. With the test lamp still connected, measure for battery voltage between the ignition 1 voltage circuit and a good ground.
    6. ⇒If the voltage is not within 0.75 volts of battery voltage, repair the high resistance in the circuit.
  6. Measure the voltage between the MAF sensor signal circuit and a good ground for 4.9-5.2 volts.
    7. ⇒If the voltage is less than 4.9 volts, test the circuit for high resistance, or an open.
    ⇒If the voltage is within 4.9-5.2 volts, test the circuit for a short to the IAT signal circuit or to any other 5-volt reference circuit.
  7. Turn OFF the ignition and all electrical accessories. Allow sufficient time for the control module to power down before taking a resistance measurement.
  8. Measure the resistance between the ground circuit of the MAF sensor and a good ground for less than 5 ohms of resistance. You should measure less than 5 ohms of resistance.
    9. ⇒If the resistance is more than 5 ohms, repair the high resistance in the ground circuit.

    Important: To set up the J 38522 , place the duty cycle to normal, the frequency to 5K, and the signal switch to 5 volts.

  9. Turn OFF the ignition and connect the red lead of the J 38522 to the signal circuit of the MAF sensor harness connector and the black lead to a good ground.
  10. Start the engine and observe the MAF sensor for a range of 4,950-5,025 Hertz.
    11. ⇒If the MAF sensor is not within the specified range, test for an intermittent or poor connection at the control module. If tests OK, replace the control module.
    ⇒If the MAF sensor is within the specified range, test for an intermittent or poor connection at the control module. If tests OK, replace the MAF sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Throttle Body Assembly Replacement