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 powertrain control module (PCM) uses the mass air flow information in order 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 may be monitored using a scan tool. The frequency varies within a range of around 2000 Hz at idle to about 10,000 Hz at maximum engine load. DTC P0101 is set if the signal from the MAF sensor does not match a predicted value based upon the barometric pressure calculated from the 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 V. |
| • | The throttle is steady and the TP angle is below 50%. |
| • | The EGR duty cycle is below 50%. |
| • | The EGR pintle position is below 50%. |
Conditions for Setting the DTC
| • | The MAF signal frequency indicates an airflow significantly higher or lower 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 illuminates the malfunction indicator lamp (MIL) the first time the malfunction is detected. |
| • | The PCM calculates an airflow value based on the idle air control valve position, the throttle position, the RPM and the barometric pressure. |
| • | The PCM stores the conditions which were present when the DTC set as Freeze Frame and the Fail Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns the MIL off during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC may be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Diagnostic Aids
Inspect for the following conditions:
| • | A skewed or stuck TP sensor. A malfunctioning TP sensor or TP sensor circuit may 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%, test for the following conditions and repair as necessary: |
| - | The throttle plate sticking or excessive deposits on the throttle plate or in the throttle bore. |
| - | The 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%, replace the TP sensor. |
| • | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. |
| • | Inspect the MAF sensor harness to ensure that the harness is not routed too closely 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 the connectors and the wiring harnesses related to the MAF sensor. A change in the display indicates 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 display 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 the measurement does not increase, inspect for a restriction. |
| • | A skewed or unresponsive MAP sensor. The barometric pressure used to calculate the default MAF value is based upon the MAP sensor reading. A skewed MAP sensor at key on causes the BARO reading to be incorrectly calculated. Also, with the engine running, an unresponsive MAP sensor due to faulty vacuum connections, a damaged vacuum source, or defective vacuum hoses, allowing unmetered air into the manifold causes 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. If a large difference between these 2 values occurs, DTC P0101 is 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 can not be duplicated, the information included in the Fail Records data may 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:
-
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 a 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 faulty 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 replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||||||
Are there any other DTC's set? | -- | Go to applicable DTC 's | ||||||||||||||
3 |
Does the scan tool indicate DTC P0101 Failed This Ign? | -- | Go to Diagnostic Aids | |||||||||||||
Are the values within the specified range? | 65-105 kPa | |||||||||||||||
Is the value within the specified range? | 29-48 kPa | |||||||||||||||
Monitor the MAP sensor display on the scan tool while slowly increasing the engine speed to 3000 RPM. Does the MAP sensor value increase as the engine speed increases? | -- | |||||||||||||||
Was a problem found? | -- | |||||||||||||||
8 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the repair? | -- | -- | |||||||||||||
9 |
Does the scan tool display Yes? | -- | ||||||||||||||
Is the voltage near the specified value? | 5 V | |||||||||||||||
Connect a test lamp between the MAF sensor ignition feed and ground circuits at the MAF sensor harness connector. Does the test lamp illuminate? | -- | |||||||||||||||
12 | Is the voltage less than the specified value? | 4.5 V | ||||||||||||||
13 |
Is the voltage near the specified value? | 0 V | ||||||||||||||
14 | Connect a test lamp between the MAF sensor ignition feed circuit and ground. Does the test lamp illuminate? | -- | ||||||||||||||
15 |
Was a problem found? | -- | ||||||||||||||
16 |
Was a problem found? | -- | ||||||||||||||
17 | Locate and repair the open in the ground circuit to the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||||
18 | Locate and repair the open in the ignition feed circuit to the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||||
19 | Locate and repair the short to voltage in the MAF signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||||
20 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement . Did you complete the repair? | -- | -- | |||||||||||||
|
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the repair? | -- | -- | ||||||||||||||
22 |
Does the scan tool indicate DTC P0101 Failed This Ign? | -- | System OK |
