For 1990-2009 cars only
DTC Descriptors
DTC P0101 : Mass Air Flow (MAF) Sensor PerformanceDTC P1101: Intake Air Flow System Performance
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
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 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 ground circuit |
| - | A MAF sensor signal 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. |
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 BARO, 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 DTC 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 P0068, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0506, P0507, P1516, P2101, P2119, P2120, P2122, P2123, P2125, P2127, P2128, P2135, P2138, P2176 are not set. |
| • | The control module state is in RUN. |
| • | The traction control is NOT ACTIVE. |
| • | The evaporative emission (EVAP) canister purge valve duty cycle is less than or equal to 100 percent. |
| • | The change in the MAP sensor is less than or equal to 5 kPa. |
| • | The change in the TP indicated angle is less than or equal to 15 percent. |
| • | The engine vacuum is less than or equal to 80 kPa. |
| • | The TP indicated angle is less than or equal to 100 percent. |
| • | The ignition voltage is between 9-18 volts. |
| • | If the ignition voltage is less than or equal to 11.5 volts, the underfaulted MAF must be less than or equal to 40 g/s. |
| • | The above criteria is met for 2 seconds. |
P1101
| • | The engine is running. |
| • | DTCs P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0335, 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
| • | 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: |
| - | The secondary ignition wires or coils |
| - | Any solenoids |
| - | Any relays |
| - | Any motors |
| • | 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. |
| • | A high resistance may cause a driveability concern before this DTC sets. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Special Tools Required
J 38522 Variable Speed Generator
Circuit/System Testing
- If P0106 or P0121 is set, diagnose first.
- Turn ON the ignition, with the engine OFF.
- Measure the battery voltage.
- Disconnect the MAF sensor.
- Connect a test lamp between the MAF sensor ignition 1 voltage circuit and a good ground.
- With the test lamp still connected, measure for battery voltage between the ignition 1 voltage circuit and a good ground.
- Measure the voltage between the MAF sensor signal circuit and a good ground for 4.9-5.2 volts.
- Turn OFF the ignition and all electrical accessories. Allow sufficient time for the control module to power down before taking a resistance measurement.
- 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.
- 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.
- Start the engine and observe the MAF sensor for a range of 4,950-5,025 Hertz.
| ⇒ | If the voltage is not within 0.75 volts of battery voltage, repair the high resistance in the circuit. |
| ⇒ | 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. |
| ⇒ | 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.
| ⇒ | If the MAF sensor is not within the specified range, test for intermittent or poor connections at the control module. If test normal, replace the control module. |
| ⇒ | If the MAF sensor is within the specified range, test for intermittent or poor connections at the control module. If test normal, replace the MAF sensor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
