Circuit Description
The Mass Air Flow (MAF) sensor measures the amount of air which passes through the sensor into the engine during a specific time. The PCM uses the mass air flow information in order to monitor the engine operating conditions for fuel delivery calculations. A large quantity of air entering the engine indicates an acceleration, or a high load situation. A small quantity of air indicates a deceleration or an idle. The MAF sensor produces a frequency signal which can be monitored using a scan tool. The frequency will vary from approximately 2000 Hertz at idle to approximately 10,000 Hertz at the maximum engine load. If the signal from the MAF sensor does not match a predicted value based on the barometric pressure, calculated from MAP at key ON, the throttle position, and the engine RPM, DTC P0101 will set.
Conditions for Running the DTC
| • | The engine is running. |
| • | The system voltage is between 9V and 16V. |
| • | The throttle is steady and the throttle position (TP) angle is less than 50 percent. |
| • | The EGR duty cycle is less than 50 percent. |
| • | The EGR pintle position is less than 50 percent. |
Conditions for Setting the DTC
| • | The MAF signal frequency indicates an airflow that is significantly higher or lower than a predicted value, based on the barometric pressure, the throttle position, and the engine RPM. |
| • | The above conditions are present for at least 12 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. |
| • | The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
| • | Inspect for a skewed TP sensor or a stuck TP sensor. A malfunctioning TP sensor or a malfunctioning TP sensor circuit can cause the PCM to incorrectly calculate the predicted mass air flow value. With the throttle closed, observe the Throttle Angle displayed on a scan tool. If the Throttle Angle reading is not 0 percent, inspect and test for the following conditions and repair any conditions as necessary: |
| - | A throttle plate that is sticking or that has excessive deposits on the throttle plate or in the throttle bore |
| - | A TP sensor signal circuit that is shorted to voltage |
| - | Faulty connections or high resistance in the TP sensor ground circuit |
| • | If none of the above conditions are noted and the Throttle Angle reading at closed throttle is not 0 percent, replace the TP sensor. |
| • | Inspect the harness connectors for the following conditions: |
| - | Backed-out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly-formed or damaged terminals |
| - | Faulty terminal-to-wire connections |
| • | Ensure that the MAF sensor harness is not routed too close to high voltage wires such as spark plug leads. |
| • | Inspect for a plugged intake air duct or a dirty air filter element. A wide-open throttle (WOT) acceleration from a stop should cause the MAF that is displayed on a scan tool to increase from approximately 4-7 gm/s at idle to 100 gm/s or more at the time of the 1-2 shift. If this does not occur, check for a restriction. |
| • | Inspect for a skewed or an unresponsive MAP sensor. The barometric pressure that is used in order to calculate the default MAF value is based on the MAP sensor reading. A skewed MAP sensor at key ON will cause the BARO reading to be incorrectly calculated. With the engine running, a MAP sensor that is unresponsive will cause inaccurate BARO reading updates during WOT conditions. Faulty vacuum connections, a damaged vacuum source, defective vacuum hoses, or unmetered air coming in to the manifold may cause the MAP sensor to be unresponsive or to be skewed. Both of these conditions result in a difference between the actual MAF sensor signal and the predicted MAF value, which is PCM-calculated. If a significant difference occurs between these two values. DTC P0101 will set. This condition may also cause abnormal IAC counts. With the IAC at an incorrect count value, a hard start condition, or a no start condition may occur. |
Many situations may lead to an intermittent condition. Perform each inspection or test as directed.
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Loose terminal connection |
| - | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| - | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
| • | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
If you are sent here from the Engine Cranks But Does Not Run, continue to follow the diagnostic table even if DTC P0101 has NOT failed this ignition.
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This step checks the MAP sensor. By disconnecting the MAF sensor, the vehicle is forced into speed density. Speed density is based on the MAP, the TP, and the engine RPM readings. With a skewed or unresponsive MAP sensor, the speed density calculation is incorrect, and vehicle may not start. For further information refer to Diagnostic Aids.
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This step checks for a skewed or a sticking MAP sensor. The MAP sensor should respond smoothly and gradually as the RPM is increased. Compare the MAP sensor of the affected vehicle to the MAP sensor of a normally-operating vehicle. If you note a large difference, replace the MAP sensor.
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This step verifies that the ignition feed voltage and a good ground are available at the MAF sensor.
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When the PCM is replaced, you must program the new PCM.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||||||||||
2 | Are any other DTCs set? | -- | Go to applicable DTC | |||||||||
Does the DTC P0103 reset? | -- | Go to Diagnostic Aids. | ||||||||||
|
Important : Do NOT clear the DTCs.
Does engine start and continue to run? | -- | |||||||||||
Does the parameter value change when the engine speed increases? | -- | |||||||||||
6 | Diagnose the MAP sensor. Refer to Manifold Absolute Pressure Sensor Circuit Diagnosis . Did you find and correct the condition? | -- | ||||||||||
7 |
Does the parameter measure at the specified value? | 0% | ||||||||||
8 |
Is the voltage near the specified value? | 5.0V | ||||||||||
Connect a test lamp between the ignition feed and the ground circuits of the MAF sensor. Does the test lamp illuminate? | -- | |||||||||||
10 | Is the voltage less than the specified value? | 4.5V | ||||||||||
11 |
Is the voltage near the specified value? | 0.0V | ||||||||||
12 | Connect a test lamp between the ignition feed circuit of the MAF sensor and a good ground. Does the test lamp illuminate? | -- | ||||||||||
13 | Inspect for a faulty connection at the MAF sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | ||||||||||
14 |
Did you find and correct the condition? | -- | ||||||||||
15 | Repair the open or excessive resistance in the ground circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||
16 | Repair the open or excessive resistance in the ignition feed circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||
17 | Locate and repair the short to voltage in the signal circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||
18 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement . Did you complete the replacement? | -- | -- | |||||||||
|
Important : You must program the replacement. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||||||||||
20 |
Does the DTC reset? | -- | System OK |
