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. 1) of the air flow sensor connector from the engine-ECU (terminal No. 129).
The power voltage is earthed to the engine-ECU (terminal No. 102) from the air flow sensor (terminal No. 4).

FUNCTION

The 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 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 Conditions

2 seconds later after the ignition switch has been in "ON" position or the engine has started up.
The battery voltage is 8 V or more.

Judgment Criterion

The sensor output voltage is 4.6 V or more (intake air temperature of below -45°C or equivalent) for 4 seconds.

The sensor output voltage is 0.1 V or less (intake air temperature of above 125°C or equivalent) for 4 seconds.

PROBABLE CAUSES

Failed intake air temperature sensor
Open/short circuit and 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 No. 6: 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: A-136 air flow 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 air flow sensor.

STEP 4. Perform resistance measurement at A-136 air flow sensor connector.

Disconnect connector, and measure at harness side.
Voltage 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: A-35 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. 4) air flow sensor connector and A-35 (terminal No. 102) 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 No. 6: 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 then perform the variant coding (Refer to GROUP 00 - Precautions Before Service - How to Perform Variant Coding ).

STEP 8. Perform voltage measurement at A-136 air flow 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 13 .

Go to Step 9 .

STEP 9. Perform voltage measurement at A-35 engine-ECU connector.

Disconnect engine-ECU connector, and connect special tool power plant ECU check harness (MB991987), and then measure the voltage on the check connector.
Disconnect A-136 air flow sensor connector.
Ignition switch: ON
Voltage between terminal No. 129 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: A-35 engine-ECU connector

Q. Is the check result normal?

Check output line for open circuit.

Repair or replace the connector.

STEP 11. Connector check: A-35 engine-ECU connector

Q. Is the check result normal?

Go to Step 12 .

Repair or replace the connector.

STEP 12. Check harness between A-136 (terminal No. 1) air flow sensor connector and A-35 (terminal No. 129) engine-ECU connector.

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 A-136 air flow sensor connector.

Use special tool test harness (MB991709) to connect only terminal No. 1 and No. 4, and then measure at pick-up harness.
Ignition switch: ON
Voltage between terminal No. 1 and earth.

OK:
Ambient temperature at -20°C: 3.8 - 4.4 V
Ambient temperature at 0°C: 3.2 - 3.8 V
Ambient temperature at 20°C: 2.3 - 2.9 V
Ambient temperature at 40°C: 1.5 - 2.1 V
Ambient temperature at 60°C: 0.8 - 1.4 V
Ambient temperature at 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: A-35 engine-ECU connector

Q. Is the check result normal?

Go to Step 15 .

Repair or replace the connector.

STEP 15. Check harness between A-136 (terminal No. 1) air flow sensor connector and A-35 (terminal No. 129) engine-ECU connector.

Check output line for damage.

Q. Is the check result normal?

Go to Step 7 .

Repair the damaged harness wire.