Troubleshooting
DTC P0136 OXYGEN SENSOR CIRCUIT MALFUNCTION (BANK 1 SENSOR 2)CIRCUIT DESCRIPTION
DTC Detection 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. 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 heated oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This is used to detect the oxygen concentration in the exhaust gas and to provide the ECM with feedback control the air-fuel ratio.
When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust gas increases. And the heated oxygen sensor informs the ECM of the LEAN condition (low voltage, i. e. less than 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 heated oxygen sensor informs the ECM of the RICH condition (high voltage, i. e. more than 0.45 V). The ECM judges whether the air-fuel ratio is RICH or LEAN by voltage from the heated oxygen sensor, and controls the injection timing accordingly. However, if the malfunction of the heated oxygen sensor causes abnormal voltage output, the ECM becomes unable to perform the 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), the current flows to the heater in order to heat the sensor for the accurate oxygen concentration detection.
HINT:
- Bank 1 refers to the bank that includes cylinder No.1.
- Bank 2 refers to the bank that does not include cylinder No.1.
- Sensor 2 refers to the sensor farthest away from the engine body.
MONITOR DESCRIPTION
Typical Enabling Conditions:
Typical Malfunction Thresholds:
Component Operating Range:
O2S Test Result:
The heated oxygen sensor generates waveform of the voltage between 0 V and 1 V in response to the oxygen concentration in the exhaust gases. When the output voltage of the heated oxygen sensor is 0.55 V or more, the ECM judges that the air-fuel ratio is RICH. When it is 0.40 V or less, the ECM judges that the air-fuel ratio is LEAN.
If the rear heated oxygen sensor output does not change between RICH and LEAN during "Stop and GO" driving, the ECM interprets this as malfunction in the sensor and sets a DTC. Also, if the sensor output remains at less than 0.05 V for more than 126 seconds (when ECM monitored the sensor for 210 seconds while the air-fuel feedback is being performed), the ECM will interpret this as a fault. In either case, the ECM will turn on the MIL and set a DTC.
Wiring Diagram:
CONFIRMATION DRIVING PATTERN
a. Connect the hand held tester to the DLC3.
b. Switch the hand held tester from normal mode to the check mode.
c. Start the engine and let it idle for 60 seconds or more.
d. Drive the vehicle at 25 mph (40 km/h) or more for 40 seconds or more.
e. Let the engine idle for 10 seconds or more.
f. Perform steps (d) and (e) 12 times.
HINT: If a malfunction exists, the MIL will be illuminated during step (f).
NOTE: If the conditions in this test are not strictly followed, no malfunction will be detected. If you do not have a hand-held tester, turn the ignition switch to OFF after performing steps from (c) to (f), then perform steps (c) to (f) again.
Step 1 - 2:
Step 2 (continued) - 4:
Step 5 - 6:
Step 7:
INSPECTION PROCEDURE
HINT:
Hand-held tester only: It is possible the malfunctioning area can be found using the ACTIVE TEST A/F CONTROL operation. The A/F CONTROL operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble areas are malfunctioning or not.
a. Perform the ACTIVE TEST A/F CONTROL operation.
HINT:
The A/F CONTROL operation lowers the injection volume 12.5% or increases the injection volume 25%.
1. Connect the hand-held tester to the DLC3 on the vehicle.
2. Turn the ignition switch to ON.
3. Warm up the engine by running the engine at 2,500 rpm for approximately 90 seconds.
4. Select the item: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
5. Perform the A/F CONTROL operation with the engine in an idle condition (press the right or left button).
Result:
Heated oxygen sensor reacts in accordance with increase and decrease of injection volume:
+25 % -> rich output: More than 0.5 V
-12.5 % -> lean output: Less than 0.4 V
NOTE: There is a delay of few seconds in the sensor 1 (front sensor) output, and there is about 20 seconds delay at maximum in the sensor 2 (rear sensor).
The A/F CONTROL procedure enables the technician to check and graph the voltage outputs of both the heated oxygen sensor.
To display the graph, enter ACTIVE TEST/ A/F CONTROL/USER DATA, then select "O2S B1S1 and O2S B1S2" or "O2S B2S1 and O2S B2S2" by pressing the "YES" button followed by the "ENTER" button and then the "F4" button.
NOTE: If the vehicle is short of fuel, the air-fuel ratio becomes LEAN and heated oxygen sensor DTCs will be recorded, and the MIL then illuminates.
HINT:
- If different DTCs related to different systems that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may be open.
- Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
- A high heated oxygen sensor (sensor 1) voltage (0.55 V or more) could be caused by a rich air fuel mixture. Check for conditions that would cause the engine to run rich.
- A low heated oxygen sensor (sensor 1) voltage (0.4 V or less) could be caused by a lean air fuel mixture. Check for conditions that would cause the engine to run lean.
CHECK FOR INTERMITTENT PROBLEMS
HINT:
Hand-held tester only:
Inspect the vehicle's ECM using check mode. Intermittent problems are easier to detect when the ECM is in check mode with a hand-held tester. In check mode, the ECM uses 1 trip detection logic, which has a higher sensitivity to malfunctions than normal mode (default) using 2 trip detection logic.
a. Clear the DTCs.
b. Switch the hand-held tester from normal mode to check mode.
c. Perform a simulation test.
d. Check the connector(s) and terminal(s).
e. Wiggle the harness(s) and connector(s).