Code No. P0102: Air Flow Sensor Circuit Low Input
OPERATION
- Power is supplied by the engine control relay to the air flow sensor, and the air flow sensor is earthed through the engine-ECU connector terminal AFSE.
- The air flow sensor outputs a sensor signal, which is input into the engine-ECU connector terminal AFS.
FUNCTION
- The air flow sensor outputs current that varies in accordance with the intake air volume.
- The engine-ECU uses the amperage output by the air flow sensor and the engine speed signal in order to determine the basic injection duration of the injector.
TROUBLE JUDGEMENT
Check Condition
- More than 3 seconds have passed since the ignition switch was turn to "ON" position.
Judgement Criterion
- Air flow sensor output voltage is less than 0.2 V for 2 seconds.
FAIL-SAFE AND BACKUP FUNCTION
- Fuel control is carried out using throttle opening degree and engine speed in accordance with preset map.
- Engine output is restricted.
PROBABLE CAUSES
- Failed air flow sensor
- Open/short circuit or harness damage in air flow sensor circuit or loose connector contact
- Failed engine-ECU
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STEP 1. M.U.T.-III data list
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- Data list reference table (Refer to
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- Item 10: Air flow sensor
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Q.
Is the check result normal?
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 Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
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 Go to Step 2.
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STEP 2. Voltage measurement at air flow sensor connector (power supply line).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(3)Check the voltage between the air flow sensor connector (power supply line) and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 3.
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Repair or replace the connector(s), or check and repair the harness of short to earth, and open circuit in power supply line between engine control relay connector and air flow sensor connector.
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STEP 3. Resistance measurement at air flow sensor connector (AFSE line).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Check the resistance between the air flow sensor connector (AFSE line) and body earth.
OK: Continuity (2 Ω or less)
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Q.
Is the check result normal?
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Go to Step 6.
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Go to Step 4.
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STEP 4. Check of open circuit and damage in AFSE line between air flow sensor connector and engine-ECU connector.
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Q.
Is the check result normal?
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Go to Step 5.
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Repair the connector(s) or wiring harness.
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STEP 5. M.U.T.-III data list
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- Data list reference table (Refer to ).
- Item 10: Air flow sensor
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
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Replace the engine-ECU.
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STEP 6. Check of harness damage in power supply line between engine control relay connector and air flow sensor connector.
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Q.
Is the check result normal?
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Go to Step 7.
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Repair the connector(s) or wiring harness.
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STEP 7. Check of short to earth, open circuit and damage in AFS line between air flow sensor connector and engine-ECU connector.
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Q.
Is the check result normal?
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Go to Step 8.
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Repair the connector(s) or wiring harness.
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STEP 8. M.U.T.-III diagnosis code
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- Reconfirmation of diagnosis code.
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Q.
Is diagnosis code set?
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Go to Step 9.
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
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STEP 9. Replace the air flow sensor
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- After replacing the air flow sensor, reconfirm whether the diagnosis code is set.
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Q.
Is diagnosis code set?
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Replace the engine-ECU.
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Check end.
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