Circuit Description
The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The powertrain control module (PCM) 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 signal circuit |
The PCM 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 PCM 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 (TP) sensor |
| • | The engine speed (RPM) |
The PCM 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 PCM 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 P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0401, P0403, P0404, P0405, P0440, P0442, P0443, P0446, P0449, P1404, P1441 are not set. |
| • | The engine is running. |
| • | The ignition 1 signal is between 9-18 volts. |
| • | The TP sensor angle is less than 25 percent. |
| • | The change in the TP sensor angle is less than 1.5 percent. |
| • | The MAP sensor is less than 63 kPa. |
| • | The change in the MAP sensor is less than 3 kPa. |
| • | The above conditions are met for more than 5 seconds. |
Conditions for Setting the DTC
The PCM detects that the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value for more than 10 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: |
| - | 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 acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 7-12 g/s at idle to 130 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. |
| • | Inspect for a skewed or stuck TP sensor. |
| • | The barometric pressure that is used 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 sensor 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 display varies with the altitude. With the ignition ON and the engine OFF, 103 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. |
| • | A high resistance on the signal or the low reference circuit of the ECT sensor may cause this DTC to set. |
| • | If the condition is intermittent, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step will determine if the MAP sensor pressure is within the proper range for a given altitude.
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This step will determine if the MAP sensor voltage is within the proper range at idle.
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This step will determine if the MAP sensor responds properly to the change in manifold pressure.
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This step will determine if the TP sensor is operating properly.
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This step will determine if any mechanical faults have caused this DTC to set.
Step | Action | Values | Yes | No | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | ||||||||||||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||||||||||||
2 | Attempt to start the engine. Does the engine start? | -- | Go to Step 3 | Go to Step 5 | ||||||||||||||||||
3 | Observe the Diagnostic Trouble Code (DTC) Information with the scan tool. Does the scan tool display any other DTCs set? | -- | Go to Step 4 | |||||||||||||||||||
4 |
Did the DTC fail this ignition? | -- | Go to Step 5 | Go to Diagnostic Aids | ||||||||||||||||||
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Important:: The Altitude vs. Barometric Pressure table indicates a pressure range for a given altitude under normal weather conditions. Weather conditions consisting of very low or very high pressure and/or temperature may cause a reading to be slightly out of range.
Is the MAP sensor pressure within the specified range as indicated on the Altitude vs Barometric Pressure table? | -- | Go to Step 6 | ||||||||||||||||||||
Is the MAP sensor parameter within the specified range? | 0.8-2.5 V | Go to Step 7 | ||||||||||||||||||||
Does the MAP sensor parameter change smoothly and gradually through the specified range of the test? | -- | Go to Step 8 | ||||||||||||||||||||
Does the TP sensor parameter change from the first value to the second value? | 0-100% | Go to Step 9 | Go to DTC P0121 | |||||||||||||||||||
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 | |||||||||||||||||||
10 |
Is the voltage less than the specified value? | B+ | Go to Step 12 | Go to Step 11 | ||||||||||||||||||
11 | Test for an intermittent and for a poor connection at the MAF sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 | ||||||||||||||||||
12 | Repair the high resistance in the ignition 1 voltage circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- | ||||||||||||||||||
13 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||||||||||||||||
14 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 15 | ||||||||||||||||||
15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||||||||
