Code No. P0098: No. 2 Intake Air Temperature Sensor Circuit High Input

OPERATION

A power voltage of 5 V is applied to the No. 2 intake air temperature sensor output terminal (terminal No. 1) of air flow sensor connector from the engine-ECU (terminal No. 98).
The power voltage is earthed to the engine-ECU (terminal No. 97) from the No. 2 intake air temperature sensor (terminal No. 2).

FUNCTION

The No. 2 intake air temperature sensor converts the intake air temperature into a voltage and inputs the voltage signal to the engine-ECU.
In response to the signal, the engine-ECU corrects the fuel injection amount, etc.
The No. 2 intake air temperature sensor is a kind of resistor, which has characteristics to reduce its resistance as the intake air temperature rises. Therefore, the sensor output voltage varies with the intake air temperature, and becomes lower as the intake air temperature rises.

TROUBLE JUDGMENT

Check Condition

Ignition switch is "ON" position.

Judgement Criterion

No. 2 intake air temperature sensor output voltage is more than 4.6 V (corresponding to an intake air temperature of -40°C or less) for 2 seconds.

FAIL-SAFE AND BACKUP FUNCTION

Control as if the intake air temperature in the inlet manifold is 25 °C.

PROBABLE CAUSES

Failed No. 2 intake air temperature sensor
Open circuit or harness damage in No. 2 intake air temperature sensor circuit or loose connector contact
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Connector check: B-32 No. 2 intake air temperature sensor connector

Q. Is the check result normal?

	Go to Step 2.

	Repair or replace the connector.

STEP 2. Check No. 2 intake air temperature sensor itself.

Check No. 2 intake air temperature sensor itself (Refer to ).

Q. Is the check result normal?

	Go to Step 3.

	Replace the No. 2 intake air temperature sensor.

STEP 3. Perform resistance measurement at B-32 No. 2 intake air temperature sensor connector.

Disconnect connector, and measure at harness side.
Resistance between terminal No. 2 and earth.

OK: Continuity (2 Ω or less)

Q. Is the check result normal?

	Go to Step 7.

	Go to Step 4.

STEP 4. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector.

STEP 5. Check harness between B-32 (terminal No. 2) No. 2 intake air temperature sensor connector and B-09 (terminal No. 97) engine-ECU connector.

note

Before checking harness, check intermediate connector A-65, and repair if necessary.

Check earthing line for open circuit and damage.

Q. Is the check result normal?

	Go to Step 6.

	Repair the damaged harness wire.

STEP 6. M.U.T.-III diagnosis code

Reconfirmation of diagnosis code.

Q. Is diagnosis code set?

	Replace the engine-ECU.

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 7. Perform voltage measurement at B-32 No. 2 intake air temperature sensor connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 1 and earth.

OK: 4.5 - 4.9 V

Q. Is the check result normal?

	Go to Step 10.

	Go to Step 8.

STEP 8. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?

	Go to Step 9.

	Repair or replace the connector.

STEP 9. Check harness between B-32 (terminal No. 1) No. 2 intake air temperature sensor connector and B-09 (terminal No. 98) engine-ECU connector.

note

Before checking harness, check intermediate connector A-65, and repair if necessary.

Check output line for open circuit.

Q. Is the check result normal?

	Go to Step 6.

	Repair the damaged harness wire.

STEP 10. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?

	Go to Step 11.

	Repair or replace the connector.

STEP 11. Check harness between B-32 (terminal No. 1) No. 2 intake air temperature sensor connector and B-09 (terminal No. 98) engine-ECU connector.

note

Before checking harness, check intermediate connector A-65, and repair if necessary.

Check output line for damage.

Q. Is the check result normal?

	Go to Step 6.

	Repair the damaged harness wire.