Code No. P0546: No. 1 exhaust gas temperature sensor Circuit High Input

OPERATION

A power voltage of 5 V is applied to the No. 1 exhaust gas temperature sensor output terminal from the engine-ECU connector terminal DTS1.
The power voltage is earthed to the engine-ECU connector terminal DT1E from the No. 1 exhaust gas temperature sensor connector terminal.

FUNCTION

The No. 1 exhaust gas temperature sensor converts the exhaust gas temperature into a voltage and inputs the voltage signal to the engine-ECU.
Engine-ECU uses this voltage for DPF regeneration control.
The No. 1 exhaust gas temperature sensor is a kind of resistor, which has characteristics to reduce its resistance as the exhaust gas temperature rises. Therefore, the sensor output voltage varies with the exhaust gas temperature, and becomes lower as the exhaust gas 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.
Vehicle speed is 20 km/h or higher.

Judgment Criterion

The No. 1 exhaust gas temperature sensor output voltage is 4.95 V or more.

FAIL-SAFE AND BACKUP FUNCTION

The throttle valve is opened (Electrical discontinuity).
The EGR control is stopped (fully closed).
The DPF regeneration is prohibited.
The AS&G control is prohibited.

PROBABLE CAUSES

Failed No. 1 exhaust gas temperature sensor
Open circuit or harness damage in No. 1 exhaust gas temperature sensor circuit or loose connector contact
Failed engine-ECU

DIAGNOSTIC PROCEDURE

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

Refer to Data List Reference Table

Item 117: No. 1 exhaust gas temperature sensor

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 No. 1 exhaust gas temperature sensor itself.

No. 1 exhaust gas temperature sensor connector check.
Check No. 1 exhaust gas temperature sensor itself (Refer to GROUP 17 - Emission Control <DIESEL> - Diesel Particulate Filter (DPF) System - No. 1 exhaust gas temperature sensor Check ).

Q. Is the check result normal?

	Go to Step 3.

	Repair or replace the connector, or replace the No. 1 exhaust gas temperature sensor. After replacing the No. 1 exhaust gas temperature sensor, carry out the forcible DPF regeneration. (Refer to GROUP 17 - Emission Control <DIESEL> - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).

STEP 3. Perform voltage measurement at No. 1 exhaust gas temperature sensor connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal engine-ECU DTS1 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 No. 1 exhaust gas temperature sensor connector terminal and engine-ECU connector terminal DTS1.

Check output line for open 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

Refer to Data List Reference Table

Item 117: No. 1 exhaust gas temperature sensor

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 No. 1 exhaust gas temperature sensor connector.

Disconnect connector, and measure at harness side.
Resistance between terminal engine-ECU DT1E 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 No. 1 exhaust gas temperature sensor connector terminal and engine-ECU connector terminal DT1E.

Check earthing line for open circuit and 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 No. 1 exhaust gas temperature sensor connector terminal and engine-ECU connector terminal DTS1.

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.