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 Sensor Circuit Range/PerformanceDTC P1101: Mass Air Flow System 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, P1101 |
Ground | -- | P0102 | P0102 | -- | P0102 |
Circuit/System Description
P0101
| • | The mass air flow (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 sensor has the following circuits: |
| - | An ignition 1 voltage circuit. |
| - | A ground circuit. |
| - | A MAF sensor signal circuit. |
| • | The ECM 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 ECM 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 ECM 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 ECM detects the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value, DTC P0101 sets. |
P1101
| • | The intake flow rationality diagnostic provides the within-range rationality check for the MAF/ MAP and the throttle position (TP) sensors. This is an explicit model-based diagnostic containing 4 separate models for the intake system. |
| - | The throttle model describes the flow through the throttle body and is used to estimate the MAF through the throttle body as a function of , TP, IAT and estimated MAP. |
| - | The first intake manifold model describes the intake manifold and is used to estimate MAP as a function of the MAF into the manifold from the throttle body and the MAF out of the manifold caused by engine pumping. The flow into the manifold from the throttle uses the MAF estimate calculated from the above throttle model. |
| - | The second intake manifold model is identical to the first intake manifold model except that the MAF sensor measurement is used instead of the throttle model estimate for the throttle air input. |
| - | The fourth model is created from the combination and additional calculations of the throttle model and the first intake manifold model. |
| • | The estimates of MAF and MAP obtained from this system of models and calculations are then compared to the actual measured values from the MAF, MAP and the TP sensors and to each other to determine the appropriate DTC to fail. The following table illustrates the possible failure combinations and the resulting or DTCs. |
Throttle Model | First Intake Manifold Model | Second Intake Manifold Model | Fourth Model | DTCs Passed | DTCs Failed |
|---|---|---|---|---|---|
X | X | Pass | Pass | P0101, P0106, P0121, P1101 | None |
Pass | Pass | Failed | Pass | P0101, P0106, P0121, P1101 | None |
Failed | Pass | Failed | Pass | P0106, P0121, P1101 | P0101 |
Pass | Failed | Failed | Pass | P0101, P0121, P1101 | P0106 |
Failed | Failed | Failed | Pass | P0121, P1101 | P0101, P0106 |
X | X | Pass | Failed | P0101, P0106, P1101 | P0121 |
Pass | Pass | Failed | Failed | P0101, P0106, P0121, P1101 | None |
Failed | Pass | Failed | Failed | P0101, P0106, P0121 | P1101 |
X | Failed | Failed | Failed | P0101, P0106, P0121 | P1101 |
Conditions for Running the DTC
P0101
| • | DTCs P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0335 or P0336 are not set. |
| • | The engine speed is between 450-6,800 RPM. |
| • | The IAT Sensor parameter is between -7°C and +125°C (19-257°F). |
| • | The ECT Sensor parameter is between 70-125°C (158-257°F). |
| • | The ignition voltage is between 9-18 volts. |
| • | This DTC runs continuously within the enabling conditions. |
P1101
| • | The engine is running. |
| • | DTCs P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0335 or P0336 are not set. |
| • | The engine coolant temperature is between 70-125°C (158-257°F). |
| • | The intake air temperature is between -7 and +125°C (+19.4 and +257°F). |
Conditions for Setting the DTC
The engine control module (ECM) detects that the actual measured airflow from the MAF, MAP and TP sensors is not within range of the calculated airflow that is derived from the system of models for more than 0.5 second.
Action Taken when the DTC Sets
DTCs P0101 or P1101 are type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0101 or P1101 are type B DTCs.
Diagnostic Aids
| Important: If DTC's P0106 or P0121 are set as current, diagnose these DTC's, prior to using this diagnostic procedure. |
| • | 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. |
| • | Using a scan tool, observe the MAF sensor parameter, depress the accelerator pedal to wide open throttle (WOT). The MAF sensor parameter should increase between 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. |
| • | A high resistance may cause a driveability concern before this DTC sets. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Special Tools Required
Commercially available variable Speed Generator
Circuit/System Testing
- Ignition ON, engine OFF.
- Measure the battery voltage.
- Disconnect the MAF sensor.
- Connect a test lamp between the MAF sensor ignition 1 voltage circuit and a known ground.
- With the test lamp still connected, measure for battery voltage between the ignition 1 voltage circuit and a known ground.
- Measure the voltage between the MAF sensor signal circuit and a known ground for 4.9-5.2 volts.
- Ignition OFF and all electrical accessories turned OFF
- Measure the resistance between the ground circuit of the MAF sensor and a known ground for less than 5 ohms of resistance.
- If all circuits test normal, replace the MAF Sensor.
| ⇒ | If the voltage is not within 0.75 volts of battery voltage, test the circuit for short to ground, short to voltage or an open/high resistance. |
| ⇒ | If the voltage is less than 4.9 volts, test the circuit for short to ground, short to voltage or an open/high resistance. |
| ⇒ | 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. |
Important: Allow sufficient time for the control module to power down before taking any resistance measurement.
| ⇒ | If the resistance is more than 5 ohms, test the circuit for short to ground, short to voltage or an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Engine Control Module Replacement for engine control module replacement, setup and programming. |
