Code No. P0102: Air flow Sensor Circuit Low Input
OPERATION
- Power is supplied by the engine control relay connector terminal to the air flow sensor connector terminal, and the air flow sensor connector terminal is earthed through the engine-ECU connector terminal AFSE&ECBE.
- The air flow sensor connector terminal outputs a sensor signal, which is input into the engine-ECU connector terminal AFS.
FUNCTION
- The air flow sensor outputs pulse signal that varies in accordance with the intake air volume.
- In response to the signal, the engine-ECU controls EGR control, etc.
TROUBLE JUDGEMENT
Check Conditions
- Battery positive voltage is 8 - 16 V
- 2 seconds later after the ignition switch has been in "ON" position or the engine has started up.
Judgement Criterion
- The air flow sensor output voltage is 0.50 V or less.
FAIL-SAFE AND BACKUP FUNCTION
- The control is performed using the previous value.
- The DPF regeneration is prohibited.
- The throttle valve is opened (Electrical discontinuity).
- The EGR control is stopped (fully closed).
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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- Refer to Data List Reference Table
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- Item 114: 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 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&ECBE line).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Measure the resistance between the air flow sensor connector (AFSE&ECBE 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&ECBE line between engine-ECU connector and air flow sensor 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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- Refer to Data List Reference Table .
- Item 114: 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 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 open circuit, short to earth, 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. Replace the air flow sensor.
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- After replacing the air flow sensor, re-check the trouble symptoms.
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Q.
Is the check result normal?
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Check end.
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Replace the engine-ECU.
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