Circuit Description
The mass air flow (MAF) sensor measures the amount of air which passes through the sensor into the engine during a given time. The PCM uses the mass air flow information to monitor engine operating conditions for fuel delivery calculations. A large quantity of air entering the engine indicates an acceleration or high load situation, while a small quantity of air indicates deceleration or idle. The MAF sensor produces a frequency signal which can be monitored using a scan tool. The frequency will vary within a range of around 2000 hertz at idle to about 10,000 hertz at maximum engine load. DTC P0101 will be set if the signal from the MAF sensor does not match a predicted value based on barometric pressure (calculated from MAP at key ON), the throttle position, and the engine RPM.
Conditions For Running The DTC
| • | The engine is running. |
| • | The system voltage is between 9 and 16 volts. |
| • | The throttle is steady and the 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 significantly more or less than a predicted value based upon 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 will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
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
Check for the following conditions:
| • | A skewed or stuck TP sensor |
| A malfunctioning TP sensor or TP sensor circuit can cause the PCM to incorrectly calculate the predicted mass air flow value. Observe the Throttle Angle displayed on the scan tool with the throttle closed. If the Throttle Angle reading is not 0 percent , check for the following conditions and repair as necessary: |
| - | Any throttle plate sticking or excessive deposits on the throttle plate or in the throttle bore |
| - | A TP sensor signal circuit shorted to voltage |
| - | A faulty connection 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. Refer to Throttle Position Sensor Replacement . |
| • | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper terminal tension. |
| • | Inspect the MAF sensor harness to ensure that the harness is not routed too close to high voltage wires such as spark plug leads. |
| • | Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving connectors and wiring harnesses related to the MAF sensor. A change in the display will indicate the location of the malfunction. |
| • | A plugged intake air duct or dirty air filter element--A wide-open throttle acceleration from a stop should cause the mass air flow displayed on a scan tool to increase from about 4-7 gm/s at idle to 100 gm/s or more at the time of the 1-2 shift. If not, check for a restriction. |
| • | A skewed or unresponsive MAP sensor--The barometric pressure used to calculate the default mass air flow value is based on the MAP sensor reading. A skewed MAP sensor at key ON will cause the BARO reading to be incorrectly calculated. Also, an unresponsive MAP sensor (due to faulty vacuum connections, damaged vacuum source, defective vacuum hoses, or unmetered air entering the manifold) will cause inaccurate BARO reading updates during wide-open throttle conditions. Both of these conditions result in a difference between the actual MAF sensor signal and the predicted MAF value (PCM calculated). If a large difference between these 2 values occurs DTC P0101 will set. This condition may also cause abnormal IAC counts. With the IAC at an incorrect count value, a hard start/no start condition may occur. |
If DTC P0101 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set. This may assist in determining how often the DTC sets.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
If sent here from the Engine Cranks But Does Not Run, continue to follow diagnostic table even if DTC P0101 has NOT failed this ignition.
-
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, TP, and engine RPM readings. With a skewed/unresponsive MAP sensor, the speed density calculation is incorrect and vehicle may not start. For further information refer to diagnostic aids.
-
This step checks for skewed or sticking MAP sensor. MAP sensor should respond smoothly and gradually as RPM is increased. Compare MAP sensor of affected vehicle to that of a normally operating vehicle. If a large difference is noted replace the MAP sensor.
-
Verifies that ignition feed voltage and a good ground are available at the MAF sensor.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||
2 | Select the DTC function on the scan tool. Does the scan tool display any other DTCs? | -- | ||
3 |
Does the scan tool indicate DTC P0101 failed this ignition? | -- | Go to Diagnostic Aids | |
4 |
Important: : DO NOT CLEAR DTCs.
Does the engine start and continue to run? | -- | ||
5 |
Does the MAP sensor parameter value change as 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 throttle angle equal the specified value? | 0 percent | ||
8 |
Does the voltage approximately equal the specified value? | 5.0 V | ||
9 | Connect a test lamp between the ignition feed and ground circuits of the MAF sensor. Does the test lamp illuminate? | -- | ||
10 | Is the voltage less than the specified value? | 4.5 V | ||
11 |
Does the voltage approximately equal the specified value? | 0.0 V | ||
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 | Inspect the MAF sensor circuits for the following conditions:
Refer to the appropriate procedure in Wiring Systems: 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 repair? | -- | -- | |
19 |
Important: : The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the repair? | -- | -- | |
20 |
Does the DTC reset? | -- | System OK |
