Code No. P0102: Air Flow Sensor Circuit Low Input

OPERATION

Power is supplied by the engine control relay (terminal No. 2) to the air flow sensor (terminal No. 2), and the air flow sensor (terminal No. 4) is earthed through the engine-ECU (terminal No. 88).
The air flow sensor (terminal No. 3) outputs a sensor signal, which is input into the engine-ECU (terminal No. 87).

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 JUDGMENT

Check Condition

More than 3 seconds have passed since the ignition switch was turned to "ON" position.

Judgement Criterion

Air flow sensor output voltage is less than 0.2 V [corresponding to an air flow rate of 0 g/sec or less] for 2 seconds.

PROBABLE CAUSES

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

DIAGNOSIS PROCEDURE

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

Refer to Data List Reference Table .

Item 10: 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. Connector check: A-06 air flow sensor connector

Q. Is the check result normal?

	Go to Step 3 .

	Repair or replace the connector.

STEP 3. Perform voltage measurement at A-06 air flow sensor connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 2 and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 5 .

	Go to Step 4 .

STEP 4. Connector check: A-33X engine control relay connector

Q. Is the check result normal?

	Check and repair harness between A-33X (terminal No. 2) engine control relay connector and A-06 (terminal No. 2) air flow sensor connector. Check power supply line for open/short circuit.

	Repair or replace the connector.

STEP 5. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?

	Go to Step 6 .

	Repair or replace the connector.

STEP 6. Check harness between A-06 (terminal No. 3) air flow sensor connector and B-09 (terminal No. 87) engine-ECU connector.

Check output line for open/short circuit and damage.

Q. Is the check result normal?

	Go to Step 7 .

	Repair the damaged harness wire.

STEP 7. Connector check: A-33X engine control relay connector

Q. Is the check result normal?

	Go to Step 8 .

	Repair or replace the connector.

STEP 8. Check harness between A-33X (terminal No. 2) engine control relay connector and A-06 (terminal No. 2) air flow sensor connector.

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 9 .

	Repair the damaged harness wire.

STEP 9. M.U.T.-III data list

Refer to Data List Reference Table

Item 10: 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 10 .

STEP 10. 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.