Circuit Description
The mass air flow (MAF) sensor measures the amount of air which passes through it 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. If the signal from the MAF sensor does not match a predicted value based on barometric pressure (calculated from MAP at key ON), throttle position, and engine RPM. DTC P0101 will set.
Conditions for Running the DTC
| • | The engine is running. |
| • | System voltage is between 9 volts and 16 volts. |
| • | The throttle is steady and TP angle is below 50 percent. |
| • | EGR duty cycle is below 50 percent. |
| • | EGR pintle position is below 50 percent. |
Conditions for Setting the DTC
| • | MAF signal frequency indicates an airflow significantly higher or lower than a predicted value based on barometric pressure, throttle position and 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 second consecutive 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/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:
| • | 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: |
| - | Throttle plate sticking or excessive deposits on the throttle plate or in the throttle bore. |
| - | TP sensor signal circuit shorted to voltage. |
| - | Poor connection or high resistance in the TP sensor ground circuit. |
| - | If none of the above conditions are found and the throttle angle reading at closed throttle is not 0 percent, replace the TP sensor. |
| • | Inspect harness connectors for the following conditions: |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Poor terminal to wire connection |
| • | Misrouted harness -- Inspect the MAF sensor harness to ensure that it is not routed too close to high voltage wires such as spark plug leads. |
| • | Damaged harness -- 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. |
| • | 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. |
| • | 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, with the engine running, an unresponsive MAP sensor 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 two 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 the DTC cannot be duplicated and is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set. Also refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This step verifies that the problem is present.
-
This step verifies a proper MAP/ BARO value at initial key ON. If the MAP sensor is stuck the barometric pressure value will be incorrectly calculated. This will cause the predicted Mass Air Flow calculations to be inaccurate. DTC P0101 will set if the MAF sensor signal does not match the predicted MAF value.
-
This step verifies a proper MAP sensor signal with engine running. With a closed throttle and proper engine vacuum, the MAP sensor signal should be between 29 kPa and 48 kPa.
-
This step verifies a proper MAP sensor response as the throttle is opened. As the throttle is steadily opened, pressure in the intake manifold increases. The MAP sensor signal should increase steady as the pressure increases.
-
Checks for conditions which can cause the DTC to be set with a normally operating MAF sensor.
-
A voltage reading of less than 4 or over 6 volts at the MAF sensor signal circuit indicates a malfunction in the wiring or a poor connection.
-
Verifies that ignition feed voltage and a good ground are available at the MAF sensor.
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Values | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||||||
Are there any other DTCs set? | -- | |||||||||||||||
3 |
Does the scan tool indicate DTC P0101 failed this ignition? | -- | Go to Diagnostic Aids | |||||||||||||
Does the value measure within the specified range? | 65-105 kPa | |||||||||||||||
Does the value measure within the specified range? | 29-48 kPa | |||||||||||||||
Monitor the MAP sensor display on the scan tool while slowly increasing engine speed to 3000 RPM. Does the MAP sensor value increase as engine speed increases? | -- | |||||||||||||||
Did you find and correct the condition? | -- | |||||||||||||||
8 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | -- | |||||||||||||
9 |
Does the scan tool display YES? | -- | ||||||||||||||
Does the voltage measure near the specified value? | 5 V | |||||||||||||||
Connect a test lamp between the MAF sensor ignition feed circuit and ground circuit at the MAF sensor harness connector. Does the test lamp illuminate? | -- | |||||||||||||||
12 | Is the voltage less than the specified value? | 4.5 V | ||||||||||||||
13 |
Does the voltage measure near the specified value? | 0 V | ||||||||||||||
14 | Connect a test lamp between MAF sensor ignition feed circuit and chassis ground. Does the test lamp illuminate? | -- | ||||||||||||||
15 |
Did you find and correct the condition? | -- | ||||||||||||||
16 |
Did you find and correct the condition? | -- | ||||||||||||||
17 | Locate and repair the open in the ground circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||||||||||
18 | Locate and repair the open in the ignition feed circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||||||||||
19 | Locate and repair the short to voltage in the MAF signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||||||||||
20 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement . Did you complete the replacement? | -- | -- | |||||||||||||
|
Important:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||||||||||||||
22 |
Does the DTC reset? | -- | System OK |
