Code No. P0112: Intake Air Temperature Sensor No. 2 Circuit Low Input

OPERATION

A power voltage of 5 V is applied to the No. 2 intake air temperature sensor No. 2 output terminal from the engine-ECU connector terminal ATS2.
The power voltage is earthed to the engine-ECU connector terminal AT2E from the No. 2 intake air temperature sensor No. 2 terminal.

FUNCTION

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

TROUBLE JUDGEMENT

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.

Judgement Criterion

The No. 2 intake air temperature sensor No. 2 output voltage is 0.05 V or less.

FAIL-SAFE AND BACKUP FUNCTION

The intake air temperature is controlled to be 50°C.
The EGR control is stopped (fully closed).

PROBABLE CAUSES

Failed No. 2 intake air temperature sensor No. 2
Short circuit in No. 2 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 8: 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. 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 3.

	Repair or replace the connector, or replace the intake air temperature sensor No. 2.

STEP 3. Perform voltage measurement at intake air temperature sensor No. 2 connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal engine-ECU ATS2 line and body earth.

OK: 4.5 - 4.9 V

Q. Is the check result normal?

	Go to Step 6.

	Go to Step 4.

STEP 4. Check harness between intake air temperature sensor No. 2 connector terminal and engine-ECU connector terminal ATS2.

Check output line for short circuit.

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector, or repair the damaged harness wire.

STEP 5. M.U.T.-III data list

Item 8: 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.

STEP 6. Perform resistance measurement at intake air temperature sensor No. 2 connector.

Disconnect connector, and measure at harness side.
Resistance between terminal engine-ECU AT2E line and body earth.

OK: Continuity (2 Ω or less)

Q. Is the check result normal?

	Go to Step 8.

	Go to Step 7.

STEP 7. Check harness between intake air temperature sensor No. 2 connector terminal and engine-ECU connector terminal AT2E.

Check earthing line for damage.

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector, or repair the damaged harness wire.

STEP 8. Check harness between intake air temperature sensor No. 2 connector terminal and engine-ECU connector terminal ATS2.

Check output line for damage.

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector, or repair the damaged harness wire.