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) A/F sensor (bank 1, 2 sensor 1) 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)
A/F sensor (bank 1, 2 sensor 1)
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 20 to 40 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

^*: 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 power switch off.
Turn the power switch on (IG) and turn the tester 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 75 to 120 km/h (47 to 75 mph) for 10 minutes or more (Step "C").

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.
Enter the following menus: Powertrain / Engine / Utility / All Readiness.
Input DTCs: P0136, P0137, P0138, P0156, P0157 and P0158.

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

Tester 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
N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

Tech Tips

If the judgment result shows NORMAL, the system is normal.
If the judgment result shows ABNORMAL, the system has a malfunction.
If the judgment result shows INCOMPLETE or N/A, perform steps (Step "C") and (Step "D") again.

CAUTION / NOTICE / HINT

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.
When viewed from the rear of the engine assembly, Bank 1 is on the left side and Bank 2 is on the right side.
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 power switch on (IG) and turn the tester ON.
Enter the following menus: Powertrain / Engine and ECT / DTC.

Read DTCs.

Result

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

CHECK EXHAUST GAS LEAK Click here

PERFORM ACTIVE TEST USING GTS (INJECTION VOLUME) Click here

GO TO DTC CHART Click here

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

Put the engine in inspection mode Click here.
Connect the GTS to the DLC3.
Turn the tester 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
Higher than 1.0 V	A
Below 1.0 V	B

PERFORM ACTIVE TEST USING GTS (INJECTION VOLUME) Click here

INSPECT HEATED OXYGEN SENSOR (CHECK FOR SHORT)

Disconnect the E65 or L49 heated oxygen (HO2) sensor connector.

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

Standard resistance

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

REPLACE HEATED OXYGEN SENSOR Click here

CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)


*1	Rear view of wire harness connector: (to ECM)

Turn the power switch off and wait for 5 minutes.
Disconnect the A13 ECM connector.

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

Standard resistance

Tester Connection	Condition	Specified Condition
A13-4 (HT1B) - A13-26 (OX1B)	Always	10 kΩ or higher
A13-3 (HT2B) - A13-27 (OX1B)	Always	10 kΩ or higher

REPLACE ECM Click here

REPAIR OR REPLACE HARNESS OR CONNECTOR

PERFORM ACTIVE TEST USING GTS (INJECTION VOLUME)

Put the engine in inspection mode Click here.
Connect the GTS to the DLC3.
Turn the tester ON.
Warm up the engine.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.

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

Tech Tips

Change the fuel injection volume within the range of -12.5% and +12.5%. The injection volume can be changed in fine graduations within the range.
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.

Result

Tester 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

Connect the GTS to the DLC3.
Turn the power switch on (READY) and turn the tester ON.
Clear DTC Click here.
Enter the following menus: Powertrain / Engine and ECT / Data List / GAS AF Control / AFS Voltage B1S1 or AFS Voltage B2S1.
Warm-up the engine until the engine coolant temperature is 75°C (167°F) or more.
Repeat the following drive pattern three times:
- Accelerate the vehicle to 80 km/h (50 mph) for 10 seconds or more.
- Move the shift lever into S3 range and decelerate the vehicle for 4 seconds or more.

Read the value.

Standard current
Less than 3.0 mA


*a	70 km/h (45 mph)
*b	0 km/h (0 mph)
*c	Warm-up
*d	4 seconds or more

REPLACE HEATED OXYGEN SENSOR Click here

REPLACE AIR FUEL RATIO SENSOR Click here

PERFORM ACTIVE TEST USING GTS (INJECTION VOLUME)
1. Put the engine in inspection mode Click here.
2. Connect the GTS to the DLC3.
3. Turn the tester ON.
4. Enter the following menus: Powertrain / Engine and ECT / Data List / GAS AF Control / O2S B1S2 or O2S B2S2.
5. After warming up the engine, run the engine at an engine speed of 2500 rpm for 3 minutes.
6. Read the output voltage of the HO2 sensor when the engine rpm is suddenly increased.
  
  Standard
  
  Fluctuates between 0.4 V or less and 0.55 V or higher.
NG
CHECK EXHAUST GAS LEAK Click here

OK

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

PERFORM ACTIVE TEST USING GTS (INJECTION VOLUME)

Put the engine in inspection mode Click here.
Connect the GTS to the DLC3.
Turn the tester ON.
Warm up the engine.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.

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

Tech Tips

Change the fuel injection volume within the range of -12.5% and +12.5%. The injection volume can be changed in fine graduations within the range.
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.

Result

Tester 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

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

REPLACE AIR FUEL RATIO SENSOR Click here

CHECK EXHAUST GAS LEAK

OK

No gas leakage.

NG
REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

OK

OK
No gas leakage.

INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

Turn the power switch off.
Disconnect the A/F sensor connector.

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

Standard resistance

Bank 1 Sensor 1
Tester Connection	Condition	Specified Condition
1 (HA1A) - 2 (+B)	20°C (68°F)	1.8 to 3.4 Ω
1 (HA1A) - 4 (A1A-)	Always	10 kΩ or higher

Bank 2 Sensor 1
Tester Connection	Condition	Specified Condition
1 (HA2A) - 2 (+B)	20°C (68°F)	1.8 to 3.4 Ω
1 (HA2A) - 4 (A2A-)	Always	10 kΩ or higher

REPLACE HEATED OXYGEN SENSOR Click here

CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM)

Disconnect the E65 or L49 HO2 sensor connector.
Disconnect the A13 and E1 ECM connectors.

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

Standard resistance (Check for open)

Terminal Connection	Condition	Specified Condition
E65-1 (HT1B) - A13-4 (HT1B)	Always	Below 1 Ω
E65-3 (OX1B) - A13-26 (OX1B)	Always	Below 1 Ω
E65-4 (E2) - E1-28 (E2)	Always	Below 1 Ω
L49-1 (HT2B) - A13-3 (HT2B)	Always	Below 1 Ω
L49-3 (OX2B) - A13-27 (OX2B)	Always	Below 1 Ω
L49-4 (E2) - E1-28 (E2)	Always	Below 1 Ω

Standard resistance (Check for short)

Terminal Connection	Condition	Specified Condition
E65-1 (HT1B) or A13-4 (HT1B) - Body ground	Always	10 kΩ or higher
E65-3 (OX1B) or A13-26 (OX1B) - Body ground	Always	10 kΩ or higher
E65-4 (E2) or E1-28 (E2) - Body ground	Always	10 kΩ or higher
L49-1 (HT2B) or A13-3 (HT2B) - Body ground	Always	10 kΩ or higher
L49-3 (OX2B) or A13-27 (OX2B) - Body ground	Always	10 kΩ or higher
L49-4 (E2) or E1-28 (E2) - Body ground	Always	10 kΩ or higher

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

Refer to 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 power switch on (IG) and turn the tester ON.
Clear the DTCs Click here.
Enter the following menus: Powertrain / Engine / 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)

END

REPLACE AIR FUEL RATIO SENSOR Click here

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

Tech Tips

Refer to 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 power switch on (IG) and turn the tester ON.
Clear the DTCs Click here.
Enter the following menus: Powertrain / Engine / 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)

END

REPLACE HEATED OXYGEN SENSOR Click here