Code No. P0135: Oxygen Sensor Heater (Front) System <SOHC>

OPERATION

Power is supplied to the heater power terminal (terminal No. 1) of the oxygen sensor (front) connector from the engine control relay (terminal No. 1).

The heater (terminal No. 3) of the oxygen sensor (front) connector is controlled by the power transistor in the engine-A/T-ECU (terminal No. 3).

function

The power supply to the oxygen sensor heater (front) is controlled by the ON/OFF control of the power transistor in the engine-A/T-ECU.

Heating the oxygen sensor heater (front) enables the oxygen sensor to provide good response even when the exhaust emission temperature is low.

TROUBLE JUDGMENT

Check Condition

Engine coolant temperature approximately 20 °C or more.

Oxygen sensor heater (front): ON

Engine speed of 50 r/min or more.

A/C relay: OFF

Radiator fan: OFF

Battery voltage 11 - 16 V

Judgment Criterion

Heater current of oxygen sensor heater (front) 0.2 A or less or 3.5 A or more for 4 seconds.

PROBABLE CAUSE

Failed oxygen sensor heater

Open/short circuit in oxygen sensor circuit or loose connector contact

Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. Connector check: B-112 oxygen sensor (front) connector

Q: Is the check result normal?

YES: Go to Step 2

.
NO: Repair.

STEP 2. Perform resistance measurement at B-112 oxygen sensor (front) connector.

Disconnect connector, and measure at sensor side.

Resistance between terminal No. 1 and No. 3.

OK: 4.8 - 8.0 Ω

Q: Is the check result normal?

YES: Go to Step 3

.
NO: Replace oxygen sensor.

STEP 3. Perform voltage measurement at B-112 oxygen sensor (front) 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?

YES: Go to Step 5

.
NO: Go to Step 4

STEP 4. Connector check: B-17X engine control relay connector

Q: Is the check result normal?

YES:

Check and repair harness between B-112 (terminal No. 1) oxygen sensor connector and B-17X (terminal No. 1) engine control relay connector.

Check power supply line for open/short circuit.

NO: Repair.

STEP 5. Perform voltage measurement at C-112 engine-A/T-ECU connector.

Measure engine-A/T-ECU terminal voltage.

Ignition switch: ON

Voltage between terminal No. 3 and earth.

OK: System voltage

Q: Is the check result normal?

YES: Go to Step 8

.
NO: Go to Step 6

STEP 6. Connector check: C-112 engine-A/T-ECU connector

Q: Is the check result normal?

YES: Go to Step 7

.
NO: Repair.

STEP 7. Check harness between B-112 (terminal No. 3) oxygen sensor (front) connector and C-112 (terminal No. 3) engine-A/T-ECU connector.

Check earthing line for open/short circuit.

Q: Is the check result normal?

YES: Replace engine-A/T-ECU.
NO: Repair.

STEP 8. Connector check: C-112 engine-A/T-ECU connector

Q: Is the check result normal?

YES: Go to Step 9

.
NO: Repair.

STEP 9. Check harness between B-112 (terminal No. 1) oxygen sensor (front) connector and B-17X (terminal No. 1) engine control relay connector.

Check power supply line for damage.

Q: Is the check result normal?

YES: Go to Step 10

.
NO: Repair.

STEP 10. Check harness between B-112 (terminal No. 3) oxygen sensor (front) connector and C-112 (terminal No. 3) engine-A/T-ECU connector.

Check earthing line for damage.

Q: Is the check result normal?

YES: Go to Step 11

.
NO: Repair.

STEP 11. Check the trouble symptoms.

Q: Does trouble symptom persist?

YES: Replace engine-A/T-ECU.
NO: Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points


Code No. P0135: Oxygen Sensor Heater (Front) System <SOHC>

OPERATION Power is supplied to the heater power terminal (terminal No. 1) of the oxygen sensor (front) connector from the engine control relay (terminal No. 1). The heater (terminal No. 3) of the oxygen sensor (front) connector is controlled by the power transistor in the engine-A/T-ECU (terminal No. 3).
function The power supply to the oxygen sensor heater (front) is controlled by the ON/OFF control of the power transistor in the engine-A/T-ECU. Heating the oxygen sensor heater (front) enables the oxygen sensor to provide good response even when the exhaust emission temperature is low.
TROUBLE JUDGMENT Check Condition Engine coolant temperature approximately 20 °C or more. Oxygen sensor heater (front): ON Engine speed of 50 r/min or more. A/C relay: OFF Radiator fan: OFF Battery voltage 11 - 16 V Judgment Criterion Heater current of oxygen sensor heater (front) 0.2 A or less or 3.5 A or more for 4 seconds.
PROBABLE CAUSE Failed oxygen sensor heater Open/short circuit in oxygen sensor circuit or loose connector contact Failed engine-A/T-ECU
	DIAGNOSIS PROCEDURE

	STEP 1. Connector check: B-112 oxygen sensor (front) connector
	Q: Is the check result normal? YES: Go to Step 2 . NO: Repair.
	STEP 2. Perform resistance measurement at B-112 oxygen sensor (front) connector.
	Disconnect connector, and measure at sensor side. Resistance between terminal No. 1 and No. 3. OK: 4.8 - 8.0 Ω Q: Is the check result normal? YES: Go to Step 3 . NO: Replace oxygen sensor.
	STEP 3. Perform voltage measurement at B-112 oxygen sensor (front) 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? YES: Go to Step 5 . NO: Go to Step 4 .
	STEP 4. Connector check: B-17X engine control relay connector
	Q: Is the check result normal? YES: Check and repair harness between B-112 (terminal No. 1) oxygen sensor connector and B-17X (terminal No. 1) engine control relay connector. Check power supply line for open/short circuit. NO: Repair.
	STEP 5. Perform voltage measurement at C-112 engine-A/T-ECU connector.
	Measure engine-A/T-ECU terminal voltage. Ignition switch: ON Voltage between terminal No. 3 and earth. OK: System voltage Q: Is the check result normal? YES: Go to Step 8 . NO: Go to Step 6 .
	STEP 6. Connector check: C-112 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Go to Step 7 . NO: Repair.
	STEP 7. Check harness between B-112 (terminal No. 3) oxygen sensor (front) connector and C-112 (terminal No. 3) engine-A/T-ECU connector.
	Check earthing line for open/short circuit. Q: Is the check result normal? YES: Replace engine-A/T-ECU. NO: Repair.
	STEP 8. Connector check: C-112 engine-A/T-ECU connector
	Q: Is the check result normal? YES: Go to Step 9 . NO: Repair.
	STEP 9. Check harness between B-112 (terminal No. 1) oxygen sensor (front) connector and B-17X (terminal No. 1) engine control relay connector.
	Check power supply line for damage. Q: Is the check result normal? YES: Go to Step 10 . NO: Repair.
	STEP 10. Check harness between B-112 (terminal No. 3) oxygen sensor (front) connector and C-112 (terminal No. 3) engine-A/T-ECU connector.
	Check earthing line for damage. Q: Is the check result normal? YES: Go to Step 11 . NO: Repair.
	STEP 11. Check the trouble symptoms. Q: Does trouble symptom persist? YES: Replace engine-A/T-ECU. NO: Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).