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### DTC P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)

### DTC P0137 Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2)

### DTC P0138 Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2)

## for Preparation Click here

HINT:

  Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.

## DESCRIPTION

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a TWC is used. For the most efficient use of the TWC, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric air-fuel level. To help the ECM to deliver accurate air-fuel ratio control, a heated oxygen sensor is used.
The heated oxygen sensor is located behind the TWC, and detects the oxygen concentration in the exhaust gas. Since the sensor is integrated with the heater that heats the sensing portion, it is possible to detect the oxygen concentration even when the intake air volume is low (the exhaust gas temperature is low).
When the air-fuel ratio becomes lean, the oxygen concentration in the exhaust gas is rich. The heated oxygen sensor informs the ECM that the post-TWC air-fuel ratio is lean (low voltage, i.e. less than 0.45 V).
Conversely, when the air-fuel ratio is richer than the stoichiometric air-fuel level, the oxygen concentration in the exhaust gas becomes lean. The heated oxygen sensor informs the ECM that the post-TWC air-fuel ratio is rich (high voltage, i.e. more than 0.45 V). The heated oxygen sensor has the property of changing its output voltage drastically when the air-fuel ratio is close to the stoichiometric level.
The ECM uses the supplementary information from the heated oxygen sensor to determine whether the air-fuel ratio after the TWC is rich or lean, and adjusts the fuel injection time accordingly. Thus, if the heated oxygen sensor is working improperly due to internal malfunctions, the ECM is unable to compensate for deviations in the primary air-fuel ratio control.

DTC No. | DTC Detection Conditions | Trouble Areas

P0136

1. Abnormal output voltage

During active air-fuel ratio control, conditions (a) and (b) are met for certain period of time (1 trip detection logic):
(a) Heated oxygen sensor voltage does not decrease to less than 0.2 V
(b) Heated oxygen sensor voltage does not increase to more than 0.6 V

1. Low impedance

Sensor impedance is less than 5 Ω for more than 30 seconds when ECM assumes sensor is being warmed up and operating normally (1 trip detection logic)

1. Open or short in heated oxygen sensor (sensor 2) circuit
2. Heated oxygen sensor (sensor 2)
3. Heated oxygen sensor heater (sensor 2)
4. Air-fuel Ratio (A/F) sensor (sensor 1)
5. EFI relay
6. Gas leakage from exhaust system

P0137

1. Low voltage (open)

During active air-fuel ratio control, conditions (a) and (b) are met for certain period of time (1 trip detection logic):
(a) Heated oxygen sensor output voltage is less than 0.21 V
(b) Target air-fuel ratio rich

1. High impedance

Sensor impedance is 15 Ω or more for more than 90 seconds when ECM assumes sensor is being warmed up and operating normally (1 trip detection logic)

1. Open in heated oxygen sensor (sensor 2) circuit
2. Heated oxygen sensor (sensor 2)
3. Heated oxygen sensor heater (sensor 2)
4. EFI relay
5. Gas leakage from exhaust system

P0138

1. High voltage (short)

During active air-fuel ratio control, conditions (a) and (b) are met for certain period of time (1 trip detection logic):
(a) heated oxygen sensor output voltage is 0.59 V or more
(b) Target air-fuel ratio lean

1. Extremely high voltage (short)

Heated oxygen sensor output voltage exceeds 1.2 V for more than 10 seconds (1 trip detection logic)

1. Short in heated oxygen sensor (sensor 2) circuit
2. Heated oxygen sensor (sensor 2)
3. ECM internal circuit malfunction

## WIRING DIAGRAM

## CONFIRMATION DRIVING PATTERN

HINT:

1. This confirmation driving pattern is used in the following diagnostic troubleshooting inspection procedure when using the intelligent tester.
2. Performing this confirmation pattern will activate the heated oxygen sensor monitor (the catalyst monitor is performed simultaneously). This is very useful for verifying the completion of a repair.

(a) Connect the intelligent tester to the DLC3.
(b) Turn the ignition switch ON and turn the intelligent tester ON.
(c) Change the ECM from normal mode to check mode using the intelligent tester.
(d) Start the engine.
(e) Allow the engine to idle for 2 minutes.
(f) Warm up the engine until the engine coolant temperature reaches more than 75°C (167°F)
(g) Drive the vehicle between 64 and 113 km/h (40 and 70 mph) for at least 10 minutes.
(h) Stop the vehicle and allow the engine to idle for 20 seconds or more.

HINT:

  If a malfunction exists, the MIL will illuminate during step (g).

NOTICE:

  If the conditions in this test are not strictly followed, detection of a malfunction will not occur.

## INSPECTION PROCEDURE

HINT:

  Intelligent tester only:

  Malfunctioning areas can be identified by performing the A/F Control function provided in the Active Test. The A/F Control function can help to determine whether the Air-fuel Ratio (A/F) sensor, heated oxygen (HO2) sensor and other potential trouble areas are malfunctioning.

  The following instructions describe how to conduct the A/F control operation using intelligent tester.

1. Connect the intelligent tester to the DLC3.
2. Start the engine and turn the tester ON.
3. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
4. On the tester, select the following menu items: Powertrain / Engine and ECT / Active Test / A/F Control.
5. Perform the A/F Control operation with the engine in an idling condition (press the right or left button to change the fuel injection volume).
6. Monitor the output voltage of the A/F and Heated oxygen sensors (AFS B1 S1 and O2S B1 S2) displayed on the tester.

HINT:

1. The A/F Control operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.
2. Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

Standard:

  Tester Display (Sensor) | Injection Volume | Status | Voltage
  AFS B1 S1 (A/F) | + 25% | Rich | Less than 3.0 V
  AFS B1 S1 (A/F) | - 12.5% | Lean | More than 3.35 V
  O2S B1 S2 (HO2) | + 25% | Rich | More than 0.55 V
  O2S B1 S2 (HO2) | - 12.5% | Lean | Less than 0.4 V

NOTICE:

  The A/F sensor output has a few seconds of delay and the heated oxygen sensor output has about 20 seconds of delay at maximum.

Case | A/F Sensor (Sensor 1) Output Voltage | HO2 Sensor (Sensor 2) Output Voltage | Main Suspected Trouble Areas
1 | Injection Volume +25% -12.5% |  | Injection Volume +25% -12.5% |  | -
Output Voltage More than 3.35 V Less than 3.0 V |  | Output Voltage More than 0.55 V Less than 0.4 V |

2

Injection Volume
+25%
-12.5%

Injection Volume
+25%
-12.5%

1. A/F sensor
2. A/F sensor heater
3. A/F sensor circuit

Output Voltage Almost no reaction |  | Output Voltage More than 0.55 V Less than 0.4 V |

3

Injection Volume
+25%
-12.5%

Injection Volume
+25%
-12.5%

1. HO2 sensor
2. HO2 sensor heater
3. HO2 sensor circuit

Output Voltage More than 3.35 V Less than 3.0 V |  | Output Voltage Almost no reaction |

4

Injection volume
+25%
-12.5%

Injection Volume
+25%
-12.5%

1. Injector
2. Fuel pressure
3. Gas leakage from exhaust system
   (Air-fuel ratio extremely lean or rich)

Output Voltage Almost no reaction |  | Output Voltage Almost no reaction |

The following A/F Control procedure enables the technician to check and graph the output voltage of both A/F sensor and heated oxygen sensor.
To display the graph, select the following menu items on the tester: View / Line graph.

HINT:

1. Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, 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.
2. A low A/F sensor voltage could be caused by a rich air-fuel mixture. Check the conditions that would cause the engine to run with the rich air-fuel mixture.
3. A high A/F sensor voltage could be caused by a lean air-fuel mixture. Check the conditions that would cause the engine to run with the lean air-fuel mixture.

1.CHECK OTHER DTC OUTPUT

1. Read the DTC using the intelligent tester.

   Result:

     Display (DTC Output) | Proceed to
     P0138 is output | A
     P0137 is output | B
     P0136 is output | C

   HINT:
     If any codes besides P0136, P0137 and / or P0138 are output, perform the troubleshooting for those codes first.

| B |

Go to step 10

| C |

Go to step 7

A |

2.READ VALUE OF DATA LIST

1. Connect the intelligent tester to the DLC3.

1. Turn the ignition switch ON and turn the intelligent tester ON.

1. Enter the following menus: Powertrain / Engine and ECT / Data List / O2S B1 S2.

1. Run the engine at idle.

1. Read the output voltage of the heated oxygen sensor during idling.

   Result:

     Heated Oxygen Sensor Output Voltage | Proceed to
     More than 1.2 V | A
     Less than 1.0 V | B

| B |

Go to step 5

A |

3.CHECK WIRE HARNESS (CHECK FOR SHORT)

1. Turn the ignition switch OFF and wait for 5 minutes.

1. Disconnect the E12 ECM connector.

1. Measure the resistance of the wire harness side connectors.

   Standard resistance:

     Tester Connection | Specified Condition
     E12-2 (HT1B) - E12-25 (OX1B) | 10 kΩ or higher
     E12-2 (HT1B) - E12-28 (E2) | 10 kΩ or higher

| OK |

REPLACE ECM

NG |

4.INSPECT HEATED OXYGEN SENSOR (CHECK FOR SHORT)

1. Disconnect the H7 sensor connector.

1. Measure the resistance of the sensor.

   Standard resistance:

     Tester Connection | Specified Condition
     2 (+B) - 4 (E) | 10 kΩ or higher
     2 (+B) - 3 (OX) | 10 kΩ or higher

| OK |

REPAIR OR REPLACE HARNESS AND CONNECTOR

NG |

REPLACE HEATED OXYGEN SENSOR

5.PERFORM CONFIRMATION DRIVING PATTERN

NEXT |

6.READ OUTPUT DTC (CHECK MODE)

1. Change the ECM to check mode with the intelligent tester. Enter the following menus: Powertrain / Engine and ECT / Check Mode.

1. Warm up the engine and drive the vehicle at over 40 km/h (25 mph) for an accumulated total of 10 minutes.

   HINT:
     The 10 minutes of driving should be driven in one instance, but it is not necessary to maintain a speed of 40 km/h (25 mph) for 10 minutes consecutively.

1. Read the DTC.

   Result:

     Display (DTC output) | Proceed to
     P0136 is output | A
     No DTC | B

| B |

CHECK FOR INTERMITTENT PROBLEMS

A |

REPLACE HEATED OXYGEN SENSOR

7.READ VALUE OF DATA LIST

1. After warming up the engine, run the engine at 2,500 rpm for 3 minutes.

1. Read the output voltage of the heated oxygen sensor when the engine rpm is suddenly increased.

   HINT:
     Quickly accelerate the engine to 4,000 rpm 3 times by depressing the accelerator pedal.

   Heated oxygen sensor output voltage:
     Alternates between 0.4 V or less and 0.5 V or more.

| OK |

Go to step 12

NG |

8.CHECK FOR EXHAUST GAS LEAKAGE

OK:
  No gas leakage.

| NG |

REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

OK |

9.INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

1. Disconnect the H7 sensor connector.

1. Measure the resistance of the sensor.

   Standard resistance:

     Tester Connection | Condition | Specified Condition
     2 (+B) -1 (HT) | 20°C (68°F) | 11 to 16 Ω
     1 (HT) - 4 (E) | Always | 10 kΩ or higher

| NG |

REPLACE HEATED OXYGEN SENSOR

OK |

10.CHECK INTEGRATION RELAY (MAIN RELAY)

1. Remove the integration relay from the engine room junction block.

1. Measure the voltage of the MAIN relay.

   Standard voltage:

     Tester Connection | Condition | Specified Condition
     1J-5 - Body ground | Ignition switch ON | 10 to 14 V

| NG |

REPLACE INTEGRATION RELAY

OK |

11.CHECK WIRE HARNESS (HEATED OXYGEN SENSOR - ECM)

1. Disconnect the H7 heated oxygen sensor connector.

1. Disconnect the E12 ECM connector.

1. Measure the resistance of the wire harness side connectors.

   Standard resistance:

     Tester Connection | Specified Condition
     H7-1 (HT) - E11-2 (HT1B) H7-3 (OX) - E11-25 (OX1B) | Below 1 Ω
     H7-1 (HT) - E11-2 (HT1B) - Body ground H7-3 (OX) - E11-25 (OX1B) - Body ground | 10 kΩ or higher

| NG |

REPAIR OR REPLACE HARNESS AND CONNECTOR

OK |

REPLACE HEATED OXYGEN SENSOR

12.PERFORM CONFIRMATION DRIVING PATTERN

HINT:

  Clear all DTCs prior to performing the confirmation driving pattern.

NEXT |

13.READ OUTPUT DTC (DTC P0136 IS OUTPUT AGAIN)

1. Read DTC using the intelligent tester.

   Result:

     Display (DTC Output) | Proceed to
     P0136 is not output again | A
     P0136 is output again | B

| A |

CHECK FOR INTERMITTENT PROBLEMS

B |

14.REPLACE HEATED OXYGEN SENSOR

NEXT |

15.PERFORM CONFIRMATION DRIVING PATTERN

HINT:

  Clear all DTCs prior to performing the confirmation driving pattern.

NEXT |

16.READ OUTPUT DTC (DTC P0136 IS OUTPUT AGAIN)

1. Read DTC using the intelligent tester.

   Result:

     Display (DTC Output) | Proceed to
     P0136 is not output again | A
     P0136 is output again | B

| A |

REPAIR COMPLETED

B |

17.PERFORM ACTIVE TEST (INJECTOR VOLUME)

1. Start the engine and warm it up.

1. Connect the intelligent tester to the DLC3.

1. Turn ON the ignition switch and the intelligent tester main switch.

1. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.

1. Using the intelligent tester, change the injection volume to check the A/F sensor output and heated oxygen sensor output values below.

   HINT:
   1. Change the fuel injection volume within the range of -12 and +12%. The injection volume can be changed in 1% graduations within the range.
   2. The A/F sensor is displayed as AFS B1 S1, and the HO2 sensor is displayed as O2S B1 S2.

   Result:
   Tester Display (Sensor) | Voltage Variations | Proceed to
   AFS B1 S1 (A/F) | Alternates between more and less than 3.3 V | OK
   AFS B1 S1 (A/F) | Remains at more than 3.3 V | NG
   AFS B1 S1 (A/F) | Remains at less than 3.3 V | NG

   HINT:
     A normal HO2 sensor voltage (O2S B1 S2) reacts in accordance with increases and decreases in fuel injection volumes. When the A/F sensor voltage remains at either less than or more than 3.3 V despite the HO2 sensor indicating a normal reaction, the A/F sensor is malfunctioning.

| OK |

REPLACE AIR FUEL RATIO SENSOR

NG |

CHECK AND REPLACE EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO (INJECTOR, FUEL PRESSURE, GAS LEAKAGE IN EXHAUST SYSTEM, ETC.)