Code No. P0110: Intake Air Temperature Sensor System

OPERATION

A power voltage of 5 V is applied to the intake air temperature sensor output terminal (terminal No. 3) of the manifold absolute pressure sensor connector from the engine-ECU (terminal No. 89).
The power voltage is earthed to the engine-ECU (terminal No. 46) from the manifold absolute pressure sensor (terminal No. 4).

FUNCTION

The intake air temperature sensor converts the intake air temperature into a voltage and inputs it to the engine-ECU.
In response to the signal, the engine-ECU corrects the fuel injection amount, etc.
The 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

2 seconds later after the ignition switch has been in ON position or just after the engine has started up.

Judgment Criterion

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.

Intake air temperature sensor output voltage is less than 0.2 V (corresponding to an intake air temperature of 120°C or more) for 2 seconds.

PROBABLE CAUSES

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

DIAGNOSIS PROCEDURE

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

Item 5: Intake air temperature sensor

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: B-12 manifold absolute pressure sensor connector

Q. Is the check result normal?

	Go to Step 3 .

	Repair or replace the connector.

STEP 3. Check intake air temperature sensor itself.

Check intake air temperature sensor itself (Refer to ).

Q. Is the check result normal?

	Go to Step 4 .

	Replace the manifold absolute pressure sensor.

STEP 4. Perform resistance measurement at B-12 manifold absolute pressure sensor connector.

Disconnect connector, and measure at harness side.
Resistance between terminal No. 4 and earth.

OK: Continuity (2 Ω or less)

Q. Is the check result normal?

	Go to Step 8 .

	Go to Step 5 .

STEP 5. Connector check: B-08 engine-ECU connector

Q. Is the check result normal?

	Go to Step 6 .

	Repair or replace the connector.

STEP 6. Check harness between B-12 (terminal No. 4) manifold absolute pressure sensor connector and B-08 (terminal No. 46) engine-ECU connector.

Check earthing line for open circuit and damage.

Q. Is the check result normal?

	Go to Step 7 .

	Repair the damaged harness wire.

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

Item 5: Intake air temperature sensor

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.

STEP 8. Perform voltage measurement at B-12 manifold absolute pressure sensor connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 3 and earth.

OK: 4.5 - 4.9 V

Q. Is the check result normal?

	Go to Step 13 .

	Go to Step 9 .

STEP 9. Perform voltage measurement at B-09 engine-ECU connector.

Disconnect engine-ECU harness, and connect special tool power plant ECU check harness (MB992110) to measure at connector for inspection.
Disconnect B-12 manifold absolute pressure sensor connector.
Ignition switch: ON
Voltage between terminal No. 89 and earth.

OK: 4.5 - 4.9 V

Q. Is the check result normal?

	Go to Step 10 .

	Go to Step 11 .

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

Q. Is the check result normal?

	Check intermediate connector A-11, and repair if necessary. If intermediate connector is normal, check and repair harness between B-12 (terminal No. 3) manifold absolute pressure sensor connector and B-09 (terminal No. 89) engine-ECU connector. Check output line for open circuit.

	Repair or replace the connector.

STEP 11. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?

	Go to Step 12 .

	Repair or replace the connector.

STEP 12. Check harness between B-12 (terminal No. 3) manifold absolute pressure sensor connector and B-09 (terminal No. 89) engine-ECU connector.

note

Before checking harness, check intermediate connector A-11, and repair if necessary.

Check output line for short circuit.

Q. Is the check result normal?

	Go to Step 7 .

	Repair the damaged harness wire.

STEP 13. Perform voltage measurement at B-12 manifold absolute pressure sensor connector.

Use special tool test harness (MB991348) to connect only terminal No. 3 and No. 4, and then measure at pick-up harness.
Ignition switch: ON
Voltage between terminal No. 3 and earth.

OK:
Ambient temperature -20°C: 3.8 - 4.4 V
Ambient temperature 0°C: 3.2 - 3.8 V
Ambient temperature 20°C: 2.3 - 2.9 V
Ambient temperature 40°C: 1.5 - 2.1 V
Ambient temperature 60°C: 0.8 - 1.4 V
Ambient temperature 80°C: 0.4 - 1.0 V

Q. Is the check result normal?

	Go to Step 7 .

	Go to Step 14 .

STEP 14. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?

	Check intermediate connector A-11, and repair if necessary. If intermediate connector is normal, check harness between B-12 (terminal No. 3) manifold absolute pressure sensor connector and B-09 (terminal No. 89) engine-ECU connector. Check output line for damage.

	Repair or replace the connector.