Troubleshooting

DTC P0136 OXYGEN SENSOR CIRCUIT MALFUNCTION (BANK 1 SENSOR 2)

CIRCUIT DESCRIPTION

DTC Detecting Condition:

To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way catalytic converter is used, but for the most efficient use of the three-way catalytic converter, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio.

The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust gas and provide feedback to the computer for control of the air-fuel ratio.

When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen sensor informs the ECM of the LEAN condition (small electromotive force: < 0.45 V).

When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio the oxygen concentration in the exhaust gas is reduced and the oxygen sensor informs the ECM of the RICH condition (large electromotive force: > 0.45 V). The ECM judges by the electromotive force from the oxygen sensor whether the air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sensor causes output of abnormal electromotive force, the ECM is unable to perform accurate air-fuel ratio control.

The heated oxygen sensors include a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low) current flows to the heater to heat the sensor for accurate oxygen concentration detection.

HINT:
- Bank 1 refers to bank that includes cylinder No.1.
- Bank 2 refers to bank that does not include cylinder No.1.
- Sensor 2 refers to the sensor farther away from the engine body.

Wiring Diagram:

Confirmation Driving Pattern:

CONFIRMATION DRIVING PATTERN
1. Connect the LEXUS hand-held tester to the DLC3.
2. Switch the LEXUS hand-held tester from the Normal Mode 10 the Check (Test) Mode.
3. Start the engine and let the engine idle for 60 seconds or more.
4. Drive the vehicle at 30 km/h (18 mph) or more for 40 seconds or more.
5. Let the engine idle for 10 seconds or more.
6. Perform steps (4) to (5) 11 times.

HINT: If a malfunction exists, the check engine warning light will be indicated on the multi information display during step (6).

NOTE: If the conditions in this test are not strictly followed, detection of the malfunction will not be possible. If you do not have a LEXUS hand-held tester, turn the ignition switch OFF after performing steps (3) to (6), then perform steps (3) to (6) again.

Step 1 - 2:

Step 3:

INSPECTION PROCEDURE