DTC Descriptors
DTC P0101: Mass Air Flow (MAF) Sensor PerformanceDTC P1101: Intake Air Flow System Performance
Diagnostic Fault Information
Important: Always 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 |
Typical Scan Tool Data
Circuit | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
Ignition 1 Voltage | -- | 0 Hz | 0 Hz | -- |
MAF Sensor Signal | 1,700-9,500 Hz | 0 Hz | 0 Hz | 0 Hz |
Ground | -- | -- | 0 Hz | -- |
Circuit Description
The intake flow rationality diagnostic provides the within-range rationality check for the mass air flow (MAF), manifold absolute pressure (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 barometric pressure (BARO), TP, intake air temperature (IAT), and estimated MAP. The information from this model is displayed on the scan tool as the MAF Performance Test parameter. |
| • | 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 information from this model is displayed on the scan tool as the MAP Performance Test 1 parameter. |
| • | 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 information from this model is displayed on the scan tool as the MAP Performance Test 2 parameter. |
| • | The fourth model is created from the combination and additional calculations of the throttle model and the first intake manifold model. The information from this model is displayed on the scan tool as the TP Performance Test parameter. |
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.
MAF Performance Test | MAP Performance Test 1 | MAP Performance Test 2 | TP Performance Test | DTCs Passed | DTCs Failed |
|---|---|---|---|---|---|
-- | -- | OK | OK | P0101, P0106, P0121, P1101 | None |
OK | OK | Fault | OK | P0101, P0106, P0121, P1101 | None |
Fault | OK | Fault | OK | P0106, P0121, P1101 | P0101 |
OK | Fault | Fault | OK | P0101, P0121, P1101 | P0106 |
Fault | Fault | Fault | OK | P0121, P1101 | P0101, P0106 |
-- | -- | OK | Fault | P0101, P0106, P1101 | P0121 |
OK | OK | Fault | Fault | P0101, P0106, P0121, P1101 | None |
Fault | OK | Fault | Fault | P0101, P0106, P0121 | P1101 |
-- | Fault | Fault | Fault | P0101, P0106, P0121 | P1101 |
Conditions for Running the DTC
| • | DTCs P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0128, P0335, P0336 are not set. |
| • | The engine speed is between 400-6,400 RPM. |
| • | The IAT Sensor parameter is between -7 and +125°C (+19 and 257°F). |
| • | The ECT Sensor parameter is between 70-125°C (158-257°F). |
| • | This DTC runs continuously within the enabling conditions. |
Conditions for Setting the DTC
The 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. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Special Tools Required
J 38522 Variable Signal Generator
Circuit/System Verification
| • | Verify the integrity of the air induction system by inspecting for the following conditions: |
| - | Any damaged components |
| - | Loose or improper installation |
| - | An air flow restriction |
| - | Any vacuum leak |
| - | Water intrusion |
| • | Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust . |
| • | 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 100 g/s or more at the time of the 1-2 shift. |
| • | A steady or intermittent high resistance of 15 ohms or more on the ignition 1 voltage circuit will cause the MAF sensor values to be skewed high by up to 60 g/s. Use the scan tool and compare the MAF Sensor parameter to a known good vehicle, under various operating conditions. |
| • | A skewed or stuck engine coolant temperature (ECT) or IAT sensor will cause the calculated models to be inaccurate and may cause this DTC to run when it should not. Refer to Temperature Versus Resistance . |
| • | The barometric pressure (BARO) that is used by the ECM to calculate the air flow models is initially based on the MAP sensor at ignition ON. When the engine is running, the ECM will continually update the BARO value near WOT using the MAP sensor and a calculation. A skewed MAP sensor will cause the BARO value to be inaccurate, Use the scan tool and compare the BARO parameter at ignition ON to the Altitude vs Barometric Pressure table. Refer to Altitude Versus Barometric Pressure . |
| • | A skewed MAP sensor will also cause the first and second intake manifold models to disagree with the actual MAP sensor measurements. Use the scan tool and compare the MAP Sensor parameter to a known good vehicle, under various operating conditions. |
Circuit/System Testing
- 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 for a proper range of 4.9-5.2 volts between the MAF sensor signal circuit and a good ground.
- Turn OFF the ignition and all electrical accessories. Allow sufficient time for all of the control modules to power down before taking a resistance measurement.
- Measure for a proper value of less than 5 ohms of resistance between the ground circuit of the MAF sensor and a good ground.
- Connect the J 38522 to the vehicle. Refer to Component Testing.
- Start the engine and observe the MAF Sensor parameter for a proper range of 4,950-5,025 Hz.
| ⇒ | If the voltage is not within 1.5 volts of battery voltage, repair the high resistance in the circuit. |
| ⇒ | If the voltage is less than 4.9 volts, test the circuit for a high resistance. |
| ⇒ | If the voltage is within the specified range, test the circuit for high resistance and 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. |
| ⇒ | 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. |
Component Testing
To determine if the ECM can properly process the MAF sensor frequency signal, connect the J 38522 to the vehicle as follows:
- Turn OFF the ignition.
- Connect the battery voltage supply, and ground the black lead.
- Connect the red lead to the signal circuit of the MAF sensor.
- Set the duty cycle switch to Normal.
- Set the Frequency switch to 5 K.
- Set the signal switch to 5 volts.
- Start the engine.
- Observe the MAF Sensor parameter for the correct range of 4,950-5,025 Hz.
Repair Instructions
Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
