Code No. P0073: Intake Air Temperature Sensor No. 2 Circuit High Input

OPERATION

A power voltage of 5 V is applied to the intake air temperature sensor No. 2 output terminal (terminal No. 1) from the engine-ECU (terminal No. 65).
The power voltage is earthed to the engine-ECU (terminal No. 75) from the intake air temperature sensor No. 2 (terminal No. 2).

FUNCTION

The intake air temperature sensor No. 2 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 intake air temperature sensor No. 2 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 fuel temperature, and becomes lower as the intake air temperature rises.

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 temperature sensor No. 2 output voltage is 4.9 V or more (the air temperature is below -40°C or equivalent) for 0.5 second.

PROBABLE CAUSES

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

DIAGNOSIS PROCEDURE

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

Item 08: Intake air temperature sensor No. 2

OK: At ambient temperature (atmospheric temperature) or equivalent.

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-136 intake air temperature sensor No. 2 connector

Q. Is the check result normal?

Go to Step 3 .

Repair or replace the connector.

STEP 3. Check intake air temperature sensor No. 2 itself.

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

Q. Is the check result normal?

	Go to Step 4 .

	Replace the intake air temperature sensor No. 2.

STEP 4. Perform voltage measurement at A-136 intake air temperature sensor No. 2 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 8 .

Go to Step 5 .

STEP 5. Connector check: C-105 engine-ECU connector

Q. Is the check result normal?

Go to Step 6 .

Repair or replace the connector.

STEP 6. Check harness between A-136 (terminal No. 1) intake air temperature sensor No. 2 connector and C-105 (terminal No. 65) engine-ECU connector.

Check output line for open circuit.

Q. Is the check result normal?

Go to Step 7 .

Repair the damaged harness wire.

STEP 7. M.U.T.-III data list

Item 08: Intake air temperature sensor No. 2

OK: At ambient temperature (atmospheric temperature) or equivalent.

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. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - How to Perform Chassis Number Writing ). After replacing the engine-ECU, register the injector identification code and learn fuel injection (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).

STEP 8. Perform resistance measurement at A-136 intake air temperature sensor No. 2 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 9 .

STEP 9. Connector check: C-105 engine-ECU connector

Q. Is the check result normal?

Go to Step 10 .

Repair or replace the connector.

STEP 10. Check harness between A-136 (terminal No. 2) intake air temperature sensor No. 2 connector and C-105 (terminal No. 75) engine-ECU connector.

Check earthing line for open circuit.

Q. Is the check result normal?

Go to Step 7 .

Repair the damaged harness wire.