SFI SYSTEM, Diagnostic DTC:P0136, P0137, P0138, P0156, P0157, P0158

DTC Code	DTC Name
P0136	Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0137	Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2)
P0138	Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2)
P0156	Oxygen Sensor Circuit Malfunction (Bank 2 Sensor 2)
P0157	Oxygen Sensor Circuit Low Voltage (Bank 2 Sensor 2)
P0158	Oxygen Sensor Circuit High Voltage (Bank 2 Sensor 2)

DESCRIPTION

Tech Tips

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

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 (Three-Way Catalytic Converter) 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. For the purpose of helping the ECM to deliver accurate air-fuel ratio control, a Heated Oxygen (HO2) sensor is used.

The HO2 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 HO2 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 HO2 sensor informs the ECM that the post-TWC air-fuel ratio is rich (high voltage, i.e. more than 0.45 V). The HO2 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 HO2 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 HO2 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 Condition	Trouble Area
P0136 P0156	Abnormal voltage output: During active air-fuel ratio control, following conditions (a) and (b) met for certain period of time (2 trip detection logic) (a) Heated Oxygen (HO2) sensor voltage does not decrease to less than 0.21 V (b) HO2 sensor voltage does not increase to more than 0.59 V	Open or short in HO2 sensor (bank 1, 2 sensor 2) circuit HO2 sensor (bank 1, 2 sensor 2) HO2 sensor heater (bank 1, 2 sensor 2) Air-Fuel Ratio (A/F) sensor (bank 1, 2 sensor 1) Gas leakage from exhaust system
P0137 P0157	Low voltage (open): During active air-fuel ratio control, following conditions (a) and (b) met for certain period of time (2 trip detection logic) (a) HO2 sensor voltage output less than 0.21 V (b) Target air-fuel ratio rich	Open in HO2 sensor (bank 1, 2 sensor 2) circuit HO2 sensor (bank 1, 2 sensor 2) HO2 sensor heater (bank 1, 2 sensor 2) Gas leakage from exhaust system
P0138 P0158	High voltage (short): During active air-fuel ratio control, following conditions (a) and (b) met for certain period of time (2 trip detection logic) (a) HO2 sensor voltage output 0.59 V or more (b) Target air-fuel ratio lean	Short in HO2 sensor (bank 1, 2 sensor 2) circuit HO2 sensor (bank 1, 2 sensor 2) ECM internal circuit malfunction A/F sensor (bank 1, 2 sensor 1)

DTC No.

DTC Detection Condition

Trouble Area

P0136

P0156

Abnormal voltage output:

During active air-fuel ratio control, following conditions (a) and (b) met for certain period of time (2 trip detection logic)
(a) Heated Oxygen (HO2) sensor voltage does not decrease to less than 0.21 V
(b) HO2 sensor voltage does not increase to more than 0.59 V

Open or short in HO2 sensor (bank 1, 2 sensor 2) circuit
HO2 sensor (bank 1, 2 sensor 2)
HO2 sensor heater (bank 1, 2 sensor 2)
Air-Fuel Ratio (A/F) sensor (bank 1, 2 sensor 1)
Gas leakage from exhaust system

P0137

P0157

Low voltage (open):

During active air-fuel ratio control, following conditions (a) and (b) met for certain period of time (2 trip detection logic)
(a) HO2 sensor voltage output less than 0.21 V
(b) Target air-fuel ratio rich

Open in HO2 sensor (bank 1, 2 sensor 2) circuit
HO2 sensor (bank 1, 2 sensor 2)
HO2 sensor heater (bank 1, 2 sensor 2)
Gas leakage from exhaust system

P0138

P0158

High voltage (short):

During active air-fuel ratio control, following conditions (a) and (b) met for certain period of time (2 trip detection logic)
(a) HO2 sensor voltage output 0.59 V or more
(b) Target air-fuel ratio lean

Short in HO2 sensor (bank 1, 2 sensor 2) circuit
HO2 sensor (bank 1, 2 sensor 2)
ECM internal circuit malfunction
A/F sensor (bank 1, 2 sensor 1)

MONITOR DESCRIPTION

Active Air-Fuel Ratio Control

The ECM usually performs air-fuel ratio feedback control so that the Air-Fuel Ratio (A/F) sensor output indicates a near stoichiometric air-fuel level. This vehicle includes active air-fuel ratio control in addition to regular air-fuel ratio control. The ECM performs active air-fuel ratio control to detect any deterioration in the Three-Way Catalytic Converter (TWC) and Heated Oxygen (HO2) sensor malfunctions (refer to the diagram below).

Active air-fuel ratio control is performed for approximately 15 to 20 seconds while driving with a warm engine. During active air-fuel ratio control, the air-fuel ratio is forcibly regulated to become lean or rich by the ECM. If the ECM detects a malfunction, one of the following DTCs is set: DTC P0136 or P0156 (abnormal voltage output), P0137 or P0157 (open circuit) or P0138 or P0158 (short circuit).
Abnormal Voltage Output of HO2 Sensor (DTCs P0136 and P0156)

While the ECM is performing active air-fuel ratio control, the air-fuel ratio is forcibly regulated to become rich or lean. If the sensor is not functioning properly, the voltage output variation is small. For example, when the HO2 sensor voltage does not decrease to less than 0.21 V and does not increase to more than 0.59 V during active air-fuel ratio control, the ECM determines that the sensor voltage output is abnormal and sets DTCs P0136 and P0156.
Open or Short in Heated Oxygen (HO2) Sensor Circuit (DTCs P0137 and P0157 or P0138 and P0158)

During active air-fuel ratio control, the ECM calculates the Oxygen Storage Capacity (OSC)^*of the Three-Way Catalytic Converter (TWC) by forcibly regulating the air-fuel ratio to become rich or lean.

If the HO2 sensor has an open or short, or the voltage output of the sensor noticeably decreases, the OSC indicates an extraordinarily high value. Even if the ECM attempts to continue regulating the air-fuel ratio to become rich or lean, the HO2 sensor output does not change.

While performing active air-fuel ratio control, when the target air-fuel ratio is rich and the HO2 sensor voltage output is 0.21 V or less (lean), the ECM interprets this as an abnormally low sensor output voltage and sets DTC P0137 or P0157. When the target air-fuel ratio is lean and the voltage output is 0.59 V or more (rich) during active air-fuel ratio control, the ECM determines that the sensor voltage output is abnormally high, and sets DTC P0138 or P0158.

Tech Tips

DTC P0138 or P0158 is also set if the HO2 sensor voltage output is more than 1.2 V for 10 seconds or more.

^*: The TWC has the capability to store oxygen. The OSC and the emission purification capacity of the TWC are mutually related. The ECM determines whether the catalyst has deteriorated, based on the calculated OSC value Click here.

WIRING DIAGRAM

CONFIRMATION DRIVING PATTERN

Connect the GTS to the DLC3.
Clear the DTCs Click here.
Turn the engine switch off.
Turn the engine switch on (IG) and turn the GTS on (Step "A").
Warm-up the engine until the engine coolant temperature is 75°C (167°F) or more (Step "B").
With the transmission in 4th gear or more, drive the vehicle at 60 to 120 km/h (37 to 75 mph) for 10 minutes or more (Step "C").
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input DTCs: P0136, P0137, P0138, P0156, P0157 and P0158.

Check the DTC judgment result (Step "D").

GTS Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
UNKNOWN	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

Check that STATUS is NORMAL. If STATUS is INCOMPLETE or UNKNOWN, perform the driving pattern adding the vehicle speed and using the second gear to decelerate the vehicle.

INSPECTION PROCEDURE

Tech Tips

GTS only:

Malfunctioning areas can be identified by performing the Control the Injection Volume function provided in the Active Test. The Control the Injection Volume for A/F Sensor 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 Control the Injection Volume for A/F Sensor operation using the GTS.

Connect the GTS to the DLC3.
Start the engine and turn the GTS ON.
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
On the GTS, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume.)
Monitor the output voltages of the A/F and HO2 sensors (AFS voltage B1S1 and O2S B1S2 or AFS voltage B2S1 and O2S B2S2) displayed on the GTS.

Tech Tips

Change the fuel injection volume within the range of -12.5% to +12.5%.
Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

GTS Display (Sensor)	Injection Volume	Status	Voltage
AFS voltage B1S1 or AFS voltage B2S1 (A/F)	+12.5%	Rich	Less than 3.0 V
AFS voltage B1S1 or AFS voltage B2S1 (A/F)	-12.5%	Lean	More than 3.35 V
O2S B1S2 or O2S B2S2 (HO2)	+12.5%	Rich	More than 0.55 V
O2S B1S2 or O2S B2S2 (HO2)	-12.5%	Lean	Less than 0.4 V

Note

The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) sensor has a maximum output delay of approximately 20 seconds.

Case	A/F Sensor (Sensor 1) Output Voltage	HO2 Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
1			-
2			A/F sensor A/F sensor heater A/F sensor circuit
3			HO2 sensor HO2 sensor heater HO2 sensor circuit
4			Injector Fuel pressure Gas leakage from exhaust system (Air-fuel ratio extremely rich or lean)

Following the Control the Injection Volume procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.
To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Gas AF Control / AFS voltage B1S1 and O2S B1S2 or AFS voltage B2S1 and O2S B2S2.

Tech Tips

If other DTCs relating to different systems that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may have an open circuit.
Read freeze frame data using the GTS. Freeze frame data records the engine condition 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.
If the OX1B wire from the ECM connector is short-circuited to the +B wire, DTC P0136 will be set.
If the OX2B wire from the ECM connector is short-circuited to the +B wire, DTC P0156 will be set.

PROCEDURE

READ DTC OUTPUT

Connect the GTS to the DLC3.
Turn the engine switch on (IG) and turn the GTS ON.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.

Result

Display (DTC Output)	Proceed to
P0138 or P0158	A
P0137 or P0157	B
P0136 or P0156	C
P0136, P0137, P0138, P0156, P0157 or P0158 and other DTCs are output	D

CHECK EXHAUST GAS LEAK Click here

PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR) Click here

GO TO DTC CHART Click here

READ VALUE USING GTS (OUTPUT VOLTAGE OF HEATED OXYGEN SENSOR)

Connect the GTS to the DLC3.
Turn the engine switch on (IG) and turn the GTS ON.
Enter the following menus: Powertrain / Engine and ECT / Data List / A/F Control System / O2S B1S2 or O2S B2S2.
Allow the engine to idle.

Read the Heated Oxygen (HO2) sensor output voltage while idling.

Result

HO2 Sensor Output Voltages	Proceed to
1.0 V or more	A
Less than 1.0 V	B

PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR) Click here

INSPECT HEATED OXYGEN SENSOR (CHECK FOR SHORT)

Text in Illustration
*1	Bank 1
*2	Bank 2
*a	Component without harness connected (Heated Oxygen Sensor)

Turn the engine switch off and wait for 5 minutes.

Disconnect the heated oxygen sensor connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

GTS Connection	Condition	Specified Condition
2 (+B) - 4 (E2)	Always	10 kΩ or higher
2 (+B) - 3 (OX1B)	Always	10 kΩ or higher
2 (+B) - 4 (E2)	Always	10 kΩ or higher
2 (+B) - 3 (OX2B)	Always	10 kΩ or higher

Reconnect the heated oxygen sensor connector.

REPLACE HEATED OXYGEN SENSOR Click here

CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)

Disconnect the ECM connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

GTS Connection	Condition	Specified Condition
A21-4 (HT1B) - A21-26 (OX1B)	Always	10 kΩ or higher
A21-3 (HT2B) - A21-27 (OX2B)	Always	10 kΩ or higher

Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE ECM Click here

PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)

Connect the GTS to the DLC3.
Start the engine and turn the GTS on.
Warm up the engine.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

Change the fuel injection volume using the GTS, and monitor the voltage output of Air-Fuel Ratio (A/F) and HO2 sensors displayed on the GTS.

Tech Tips

Change the fuel injection volume within the range of -12.5% and +12.5%.
The A/F sensor is displayed as AFS voltage B1S1 or AFS voltage B2S1, and the HO2 sensor is displayed as O2S B1S2 or O2S B2S2 on the GTS.
The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

Result

GTS Display (Sensor)

Voltage Variation

Proceed to

AFS voltage B1S1 (A/F)

AFS voltage B2S1 (A/F)

Alternates between more and less than 3.25 V

AFS voltage B1S1 (A/F)

AFS voltage B2S1 (A/F)

Remains at more than 3.25 V

AFS voltage B1S1 (A/F)

AFS voltage B2S1 (A/F)

Remains at less than 3.25 V

Tech Tips

A normal HO2 sensor voltage (O2S B1S2 or O2S B2S2) reacts in accordance with increases and decreases in fuel injection volumes. When the A/F sensor voltage remains at either less or more than 3.3 V despite the HO2 sensor indicating a normal reaction, the A/F sensor is malfunctioning.

REPLACE AIR FUEL RATIO SENSOR Click here

INSPECT AIR FUEL RATIO SENSOR
Tech Tips

This A/F sensor test is to check the A/F sensor current during the fuel-cut. When the sensor is normal, the sensor current will indicate below 2.2 mA in this test.
1. Clear DTC Click here.
2. Drive the vehicle by the drive pattern as listed below:
  1. Warm up the engine.
  2. Drive the vehicle at 40 mph (60 km/h) or more for 10 minutes or more.
  3. Stop the vehicle.
  4. Accelerate the vehicle until 40 mph (60 km/h) or more and decelerate for 3 seconds or more. Perform this three times.
3. Enter the following menus: Powertrain / Engine and ECT / Data List / Gas AF Control / AFS voltage B1S1 and AFS voltage B2S1.
4. Read the value.
  
  Standard
  
  Less than 2.2 mA
  
  Tech Tips
  
  If the Techstream shows Incomplete again, increase the vehicle speed and use the second gear to decelerate the vehicle.
OK
REPLACE HEATED OXYGEN SENSOR Click here

NG
REPLACE AIR FUEL RATIO SENSOR Click here
PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)
1. Connect the GTS to the DLC3.
2. Turn the engine switch on (IG) and turn the GTS on.
3. Start the engine.
4. Warm up the engine.
5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Gas AF Control / O2S B1S2 or O2S B2S2.
6. Change the fuel injection volume using the GTS, monitoring the voltage output of the heated oxygen sensor displayed on the GTS.
  Tech Tips
  - Change the fuel injection volume within the range of - 12.5% and +12.5%.
  - The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
  Standard
  
  Fluctuates between 0.4 V or less and 0.55 V or higher.
NG
CHECK EXHAUST GAS LEAK Click here

OK

Standard
Less than 2.2 mA

Standard
Fluctuates between 0.4 V or less and 0.55 V or higher.

PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)

Connect the GTS to the DLC3.
Start the engine and turn the GTS on.
Warm up the engine.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

Change the fuel injection volume using the GTS, and monitor the voltage output of Air-Fuel Ratio (A/F) and HO2 sensors displayed on the GTS.

Tech Tips

Change the fuel injection volume within the range of -12.5% and +12.5%.
The A/F sensor is displayed as AFS voltage B1S1 or AFS voltage B2S1, and the HO2 sensor is displayed as O2S B1S2 or O2S B2S2 on the GTS.
The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

Result

GTS Display (Sensor)

Voltage Variation

Proceed to

AFS voltage B1S1 (A/F)

AFS voltage B2S1 (A/F)

Alternates between more and less than 3.25 V

AFS voltage B1S1 (A/F)

AFS voltage B2S1 (A/F)

Remains at more than 3.25 V

AFS voltage B1S1 (A/F)

AFS voltage B2S1 (A/F)

Remains at less than 3.25 V

Tech Tips

REPLACE AIR FUEL RATIO SENSOR Click here

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

CHECK EXHAUST GAS LEAK

OK

No gas leakage.

NG
REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

OK
INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
1. Inspect the heated oxygen sensor Click here.
NG
REPLACE HEATED OXYGEN SENSOR Click here

OK

OK
No gas leakage.

CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM)

Disconnect the heated oxygen sensor connector.
Disconnect the ECM connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

GTS Connection	Condition	Specified Condition
N71-1 (HT1B) - A21-4 (HT1B)	Always	Below 1 Ω
N71-3 (OX1B) - A21-26 (OX1B)	Always	Below 1 Ω
N71-4 (E2) - F1-28 (E2)	Always	Below 1 Ω
N47-1 (HT2B) - A21-3 (HT2B)	Always	Below 1 Ω
N47-3 (OX2B) - A21-27 (OX2B)	Always	Below 1 Ω
N47-4 (E2) - F1-28 (E2)	Always	Below 1 Ω
N71-1 (HT1B) or A21-4 (HT1B) - Body ground	Always	10 kΩ or higher
N71-3 (OX1B) or A21-26 (OX1B) - Body ground	Always	10 kΩ or higher
N47-1 (HT2B) or A21-3 (HT2B) - Body ground	Always	10 kΩ or higher
N47-3 (OX2B) or A21-27 (OX2B) - Body ground	Always	10 kΩ or higher

Reconnect the heated oxygen sensor connector.
Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE HEATED OXYGEN SENSOR
1. Replace the heated oxygen sensor Click here.
NEXT
PERFORM CONFIRMATION DRIVING PATTERN

Tech Tips

Perform the Confirmation Driving Pattern.

NEXT

CHECK WHETHER DTC OUTPUT RECURS (DTC P0136, P0137, P0138, P0156, P0157 OR P0158)

Connect the GTS to the DLC3.
Turn the engine switch on (IG) and turn the GTS on.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input DTCs: P0136, P0137, P0138, P0156, P0157 and P0158.

Check the DTC monitor is NORMAL. If DTC monitor is INCOMPLETE, perform the drive pattern again by accelerating the vehicle and using the second gear to decelerate the vehicle.

Result

Display (DTC Output)

Proceed to

NORMAL

(No DTC output)

ABNORMAL

(P0136, P0137, P0138, P0156, P0157 or P0158 detected)

REPLACE AIR FUEL RATIO SENSOR Click here

END

REPLACE AIR FUEL RATIO SENSOR
1. Replace the air fuel ratio sensor Click here.
NEXT
PERFORM CONFIRMATION DRIVING PATTERN

Tech Tips

Perform the Confirmation Driving Pattern.

NEXT

CHECK WHETHER DTC OUTPUT RECURS (DTC P0136, P0137, P0138, P0156, P0157 OR P0158)

Connect the GTS to the DLC3.
Turn the engine switch on (IG) and turn the GTS on.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input DTCs: P0136, P0137, P0138, P0156, P0157 and P0158.

Check the DTC monitor is NORMAL. If DTC monitor is INCOMPLETE, perform the drive pattern again by accelerating the vehicle and using the second gear to decelerate the vehicle.

Result

Display (DTC Output)

Proceed to

NORMAL

(No DTC output)

ABNORMAL

(P0136, P0137, P0138, P0156, P0157 or P0158 detected)

REPLACE HEATED OXYGEN SENSOR Click here

END