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 JUDGMENT


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.
Judgment 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).
  • The AS&G control is prohibited.

PROBABLE CAUSES



  • Failed air flow sensor
  • Open/short circuit or harness damage in air flow sensor circuit or loose connector contact
  • Failed engine-ECU

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item 114: Air flow sensor

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Go to Step 2.

STEP 2. Perform voltage measurement at air flow sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal power supply line and body earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 3.

    Repair or replace the connector, or check and repair harness between engine control relay connector terminal and air flow sensor connector terminal.

    • Check power supply line for open/short circuit.

STEP 3. Perform resistance measurement at air flow sensor connector.

  • Disconnect connector, and measure at harness side.
  • Resistance between terminal engine-ECU AFSE&ECBE line and body earth.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?
Go to Step 6.
Go to Step 4.

STEP 4. Check harness between air flow sensor connector terminal and engine-ECU connector terminal AFSE&ECBE.

  • Check earthing line for open circuit and damage.

Q. Is the check result normal?
Go to Step 5.
Repair or replace the connector, or repair the damaged harness wire.

STEP 5. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item 114: Air flow sensor

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Replace the engine-ECU.

STEP 6. Check harness between engine control relay connector terminal and air flow sensor connector terminal.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 7.
Repair or replace the connector, or repair the damaged harness wire.

STEP 7. Check harness between air flow sensor connector terminal and engine-ECU connector terminal AFS.

  • Check output line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 8.
Repair or replace the connector, or repair the damaged harness wire.

STEP 8. Replace the air flow sensor.

  • After replacing the air flow sensor, re-check the trouble symptoms.

Q. Is the check result normal?
Check end.
Replace the engine-ECU.