P0100
DTC P0100MASS AIR FLOW SENSOR CIRCUIT MALFUNCTION (QA)
Description
- The MFI system employs a hot film type Air Flow Sensor. These Mass Air Flow Sensors convert the amount of air taken into the Engine into an electric signal by utilizing the heat transfer phenomenon between the incoming air and a heating resistor (hot film) located in the air intake.
- The features of these flow sensor types are as follows:
a. High-altitude compensation is made automatically.
b. Quick response.
c. These are no moving parts.
d. They are compact.
DTC Detecting Condition
Immediately at fault recognition
Trouble Symptom
- Erroneous idling.
- Engine stalls.
- Poor driving performance
1. Connect Subaru Select Monitor or the OBD-II General Scan Tool, and read data.
a. Turn Ignition switch to "OFF".
b. Connect Subaru Select Monitor or the OBD-II General Scan Tool to Data Link Connector.
c. Turn Ignition Switch to "ON" and Subaru Select Monitor or the OBD-II General Scan Tool switch to "ON".
d. Start Engine.
e. Read data on Subaru Select Monitor or OBD-II General Scan Tool.
Subaru Select Monitor
- Designate mode using function key.
- Function mode: F08 or F47
[CHECK] FOB: Is sensor output equal to or more than 0.3 Volts and equal to or less than 5.0 Volts?
F47: Is sensor output equal to or more than 1.3 g/sec and equal to or less than 250 g/sec?
Probable Cause: Poor connect of connectors, circuit and grounding line.
[YES]: Even if Malfunction Indicator Lamp (MIL) lights up, the circuit has returned to a normal condition at this time. A temporary poor contact of the connector or harness may be the cause. Repair harness or connector of the Mass Air Flow Sensor.
HINT: Open or short circuit between Mass Air Flow Sensor and Engine Control Module (ECM).
Poor contact of connectors for Mass Air Flow Sensor or ECM.
[NO]: Go to next [CHECK].
[CHECK]: Is the value less than 0.3 Volts (1.3 g/sec)?
[YES]: Go to step 2.
[NO]: Go to step 5.
OBD-II General Scan Tool
- For detailed operation procedures, refer to the OBD-II General Scan Tool Instruction Manual.
2. Check input signal for ECM. (Using voltage meter and Subaru Select Monitor.)
- Measure voltage between ECM and body while Engine is idling.
[CHECK]: Connector & terminal:
(B84) No. 26 - Body/0.3 Volts or less.
[YES]: Go to step 3.
[NO]: Go to next [CHECK].
[CHECK]: Is the voltage more than 0.3 Volts while shaking harness and connector of ECM and monitoring the value with Subaru Select Monitor?
[YES] Repair poor contact in ECM connector.
[No]: Replace ECM with a new one.
3. Check power supply to Mass Air Flow Sensor.
a. Turn Ignition switch to "OFF".
b. Disconnect connector from mass Air Flow Sensor.
c. Turn Ignition Switch to "ON".
d. Measure voltage between Mass Air Flow Sensor connector and body.
[CHECK]: Connector & terminal:
(B3) No. 1 - Body/10 Volts or more.
[YES]: Go to step 4.
[NO]: Repair open circuit of harness between Main Relay connector and Mass Air Flow Sensor connector.
4. Check harness connector between ECM and Mass Air Flow Sensor.
a. Turn Ignition switch to "OFF".
b. Disconnect connector from ECM.
c. Measure resistance of harness connector between ECM and Mass Air Flow Sensor.
[CHECK]: Connector & terminal:
1. (B84) No. 26 - (B3) No. 4/10 Ohms or less.
2. (B84) No. 46 - (B3) No. 3/10 Ohms or less.
3. (B84) No. 25 - (B3) No. 2/10 Ohms or less.
[YES]: Replace Mass Air Flow Sensor with a new one.
[NO]: Repair poor contact and open circuit of harness between ECM and Mass Air Flow Sensor connector.
5. Check harness.
a. Turn Ignition switch to "OFF".
b. Disconnect connector from Mass Air Flow Sensor.
c. Connect Subaru Select Monitor or OBD-II General Scan Tool to Data Link Connector.
d. urn Ignition switch to "ON"
e. Read data on Subaru Select Monitor or OBD-II General Scan Tool.
Subaru Select Monitor
- Designate mode using function key.
- Function mode: F08
[CHECK]: Is the value more than 5 Volts?
[YES]: Repair short circuit of harness between Mass Air Flow Sensor and ECM.
[NO]: Go to next [CHECK].
[CHECK]: Is there poor contact in Mass Air Flow Sensor connector?
[YES]: Repair poor contact in Mass Air Flow Sensor connector.
[NO]: Replace Mass Air Flow Sensor.
OBD-II General Scan Tool
- For detailed operation procedures, refer to OBD-II General Scan Tool Instruction Manual.