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 PerformanceDTC P1101: Intake 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 |
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 DTCs
| • | DTC P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0128, P0335, or P0336 is not set. |
| • | The engine speed is between 400-8,192 RPM. |
| • | The IAT Sensor parameter is between -7 to +125°C (+19 to +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 DTCs
The engine control module (ECM) detects that the actual measured airflow from MAF, MAP, and TP is not within range of the calculated airflow that is derived from the system of models for more than 2 seconds.
Action Taken When the DTC Sets
DTCs P0101 and P1101 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0101 and P1101 are Type B DTCs.
Diagnostic Aids
| • | A steady or intermittent high resistance of 15Ω or greater on the ignition 1 voltage circuit will cause the MAF sensor signal to be increased by as much as 60 g/s. |
| • | Depending on the current ambient temperature, and the vehicle operating conditions, a MAF sensor signal circuit that is shorted to the IAT signal circuit will increase or decrease the MAF sensor signal that is interpreted by the ECM. Additionally it may cause a rapid fluctuation in the IAT Sensor parameter. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
J 38522 Variable Signal Generator
For equivalent regional tools, refer to Special Tools.
Circuit/System Verification
- Verify that DTC P0641 or P0651 is not set.
- Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust.
- Engine operating at idle, observe the scan tool MAF Sensor parameter. The reading should be between 1,700-3,200 Hz, depending on the ECT.
- 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 greater than 100 g/s at the time of the 1-2 shift.
- Use the scan tool and compare the MAF Sensor parameter to a known good vehicle under various operating conditions.
- Verify the proper operation of the MAP sensor. A skewed MAP sensor will cause the BARO value to be inaccurate. Refer to DTC P0106.
- 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.
| ⇒ | If any of the DTCs are set, refer to DTC P0641 or P0651. |
Circuit/System Testing
- Verify the integrity of the entire air induction system by inspecting for the following conditions:
- Ignition OFF for 90 seconds, disconnect the harness connector at the B75B MAF/IAT sensor.
- Test for less than 5Ω between the ground circuit terminal B and ground.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C and ground.
- Ignition ON, test for 4.8-5.2V between the signal circuit terminal A and ground.
- Ignition OFF, connect the red lead of the J 38522 Signal Generator to the signal circuit terminal A at the B75B MAF/IAT sensor harness connector. Connect the battery voltage supply to B+. Connect the black lead to ground.
- Set the J 38522 Signal Generator Signal switch to 5V, the Frequency switch to 5K, and the Duty Cycle switch to Normal.
- Engine Idling, observe the scan tool MAF Sensor parameter. The scan tool MAF Sensor parameter should be between 4,950-5,025 Hz.
- If the circuits test normal, test or replace the B75B MAF/IAT sensor.
| • | Any damaged components |
| • | Loose or improper installation |
| • | An air flow restriction |
| • | Any vacuum leak |
| • | Water intrusion |
| • | In cold climates, inspect for any snow or ice buildup |
| • | Inspect the MAF sensor element for contamination |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM. |
| ⇒ | If the MAF Sensor parameter is not within the specified range, replace the K20 ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
