Code No. P0161: Left bank Oxygen Sensor (Rear) Heater System

OPERATION

Power is supplied to the heater power terminal (terminal No. 1) of the left bank oxygen sensor (rear) connector from the engine control relay (terminal No. 1).
The heater (terminal No. 3) of the left bank oxygen sensor (rear) connector is controlled by the power transistor in the engine-ECU <M/T> or engine-A/T-ECU <A/T> (terminal No. 18).

FUNCTION

The power supply to the left bank oxygen sensor (rear) heater is controlled by the ON/OFF control of the power transistor in the engine-ECU <M/T> or engine-A/T-ECU <A/T>.
Heating the left bank oxygen sensor (rear) heater enables the left bank oxygen sensor (rear) to provide good response even when the exhaust emission temperature is low.

TROUBLE JUDGMENT

Check Conditions

Engine coolant temperature is 20°C or higher.
Battery positive voltage is 11 - 16 V.
The engine speed is 500 r/min or more.

Judgment Criterion

Left bank oxygen sensor (rear) heater currents have continued to be 0.2 A or lower, or 5.0 A or higher for 4 seconds.

PROBABLE CAUSES

Failed left bank oxygen sensor (rear) heater
Open/short circuit in left bank oxygen sensor (rear) heater circuit or loose connector contact
Failed engine-ECU <M/T> or engine-A/T-ECU <A/T>

DIAGNOSIS PROCEDURE

STEP 1. Connector check: C-02 left bank oxygen sensor (rear) connector

Q. Is the check result normal?

	Go to Step 2 .

	Repair or replace the connector.

STEP 2. Perform resistance measurement at C-02 left bank oxygen sensor (rear) connector.

Disconnect connector, and measure at sensor side.
Resistance between terminal No. 1 and No. 3.

OK: 11 - 18 Ω

Q. Is the check result normal?

	Go to Step 3 .

	Replace the left bank oxygen sensor (rear).

STEP 3. Perform voltage measurement at C-02 left bank oxygen sensor (rear) connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 1 and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 5 .

	Go to Step 4 .

STEP 4. Connector check: B-15X engine control relay connector

Q. Is the check result normal?

	Check intermediate connector D-224, and repair if necessary. If intermediate connector is normal, check and repair harness between C-02 (terminal No. 1) left bank oxygen sensor (rear) connector and B-15X (terminal No. 1) engine control relay connector. Check power supply line for open/short circuit.

	Repair or replace the connector.

STEP 5. Perform voltage measurement at D-243 engine-ECU <M/T> connector or D-212 engine-A/T-ECU <A/T> connector.

Measure engine-ECU <M/T> or engine-A/T-ECU <A/T> terminal voltage.
Ignition switch: ON
Voltage between terminal No. 18 and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 8 .

	Go to Step 6 .

STEP 6. Connector check: D-243 engine-ECU <M/T> connector or D-212 engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

	Go to Step 7 .

	Repair or replace the connector.

STEP 7. Check harness between C-02 (terminal No. 3) left bank oxygen sensor (rear) connector and D-243 (terminal No. 18) engine-ECU <M/T> connector or D-212 (terminal No. 18) engine-A/T-ECU <A/T> connector.

note

Before checking harness, check intermediate connector D-225, and repair if necessary.

Check earthing line for open/short circuit.

Q. Is the check result normal?

	Replace the engine-ECU <M/T> or engine-A/T-ECU <A/T>.

	Repair the damaged harness wire.

STEP 8. Connector check: D-243 engine-ECU <M/T> connector or D-212 engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

	Go to Step 9 .

	Repair or replace the connector.

STEP 9. Check harness between C-02 (terminal No. 1) left bank oxygen sensor (rear) connector and B-15X (terminal No. 1) engine control relay connector.

note

Before checking harness intermediate connectors D-111 and D-224, and repair if necessary.

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 10 .

	Repair the damaged harness wire.

STEP 10. Check harness between C-02 (terminal No. 3) left bank oxygen sensor (rear) connector and D-243 (terminal No. 18) engine-ECU <M/T> connector or D-212 (terminal No. 18) engine-A/T-ECU <A/T> connector.

note

Before checking harness intermediate connector D-225, and repair if necessary.

Check earthing line for damage.

Q. Is the check result normal?

	Go to Step 11 .

	Repair the damaged harness wire.

STEP 11. M.U.T.-III diagnosis code.

Reconfirmation of diagnosis code.

Q. Does trouble symptom persist?

	Replace the engine-ECU <M/T> or engine-A/T-ECU <A/T>.

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).