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

The heated oxygen sensor is a planar type. Compared to the conventional type, the sensor and heater portions are narrower. The heat of the heater is conducted to the zirconia element through the alumina, accelerating sensor activation.

To obtain a high purification rate of carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) in the exhaust gas, a Three-Way Catalytic Converter (TWC) 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 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 (small electromotive force: 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 (large electromotive force: More than 0.45 V). The ECM judges by the electromotive force from the heated oxygen sensor whether the air fuel ratio is rich or lean and controls the injection time accordingly. If the malfunction of the heated oxygen sensor causes an output of abnormal electromotive force, 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), current flows to the heater in order to heat the sensor for accurate oxygen concentration detection.

DTC No.	DTC Detection Condition	Trouble Area
P0136 P0156	During active control, heated oxygen sensor output voltage is 0.2 to 0.6 V	Open or short in heated oxygen sensor (bank 1, 2 sensor 2) circuit Heated oxygen sensor (bank 1, 2 sensor 2) Heated oxygen sensor heater (bank 1, 2 sensor 2) Integration relay
P0136 P0156	(a) and (b) are met for more than 90 seconds (a) Estimated rear oxygen sensor temperature is less than 800°C (1,472°F) (b) Rear oxygen sensor impedance is less than 5 Ω
P0137 P0157	During active control, heated oxygen sensor output voltage is less than 0.2 V
P0137 P0157	(a) and (b) are met for more than 90 seconds (a) Estimated rear oxygen sensor temperature is less than 450°C (842°F) (b) Rear oxygen sensor impedance is more than 15 kΩ
P0138 P0158	During active control, heated oxygen sensor output voltage is more than 0.6 V
P0138 P0158	Rear oxygen sensor output voltage is 1.2 V or higher for more than 30 seconds

Tech Tips

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

WIRING DIAGRAM

CONFIRMATION DRIVING PATTERN

Tech Tips

Performing this confirmation pattern will activate the DTC detection (P0136) of the ECM. This is very useful for verifying the completion of a repair.

(a) Clear the DTC Click here.
(b) Using the tester, change the ECM from normal mode to check mode Click here.
(c) Start the engine and warm it up with all the accessory switches OFF.
(d) Deactivate the inspection mode and drive the vehicle at 70 to 120 km/h (44 to 70 mph) for 5 to 10 minutes.
(e) Read DTCs.

Note

If the conditions in this test are not strictly followed, no malfunction will be detected.

INSPECTION PROCEDURE

(a) Connect the intelligent tester to the DLC3.

Tech Tips

It is possible the malfunctioning area can be found using the Active Test "Control the injection volume for A/F sensor" operation. The Active Test can determine if the heated oxygen sensor or other potential trouble areas are malfunctioning or not.

The injection volume can be switched to -12.5% (decrease) or +25% (increase) by the Active Test.

The Active Test procedure enables a technician to check and graph the output voltage of the heated oxygen sensors.

(b) Turn the ignition switch ON.

(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the injection volume for A/F sensor.

(e) Perform the Active Test while the engine is idling.

Standard voltage

Tester Display (Sensor)	Injection Volume	Status	Voltage
AFS B1S1 or AFS B2S1 (A/F)	+25%	Rich	Less than 3.0 V
AFS B1S1 or AFS B2S1 (A/F)	-12.5%	Lean	More than 3.35 V
O2S B1S1 or O2S B2S2 (heated oxygen sensor)	+25%	Rich	More than 0.55 V
O2S B1S1 or O2S B2S2 (heated oxygen sensor)	-12.5%	Lean	Less than 0.4 V

Note

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

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			Fuel injector Fuel pressure Gas leak from exhaust system (air fuel ratio extremely rich or lean)

The following "Control the injection volume for A/F sensor" procedure enables the technician to check and graph the output voltage of both A/F sensor and heated oxygen sensor.

Tech Tips

Read freeze frame data using the intelligent tester. 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 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 a rich air fuel mixture.
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 a lean air fuel mixture.
Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.

PROCEDURE

CHECK OTHER DTC OUTPUT (BESIDES DTC P0136, P0137, P0138, P0156, P0157 AND/OR P0158)

Connect the intelligent tester to the DLC3.
Turn the ignition switch ON and turn the tester ON.
Enter the following menus: Powertrain / Engine and ECT / DTC.

Read the DTCs.

Result

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

Tech Tips

If any other codes besides P0136, P0137, P0138, P0156, P0157 and/or P0158 are output, perform troubleshooting for those DTCs first.

GO TO RELEVANT DTC CHART

READ VALUE USING INTELLIGENT TESTER (OUTPUT VOLTAGE OF HEATED OXYGEN SENSOR)
1. After warming up the engine, race the engine at 2,500 rpm for 3 minutes.
2. Read the output voltage of the heated oxygen sensor when the engine is suddenly raced.
  
  Tech Tips
  
  Quickly perform racing to 4,000 rpm 3 times by using the accelerator pedal.
  
  Standard voltage
  
  Alternates between 0.4 V or less and 0.5 V or more.
OK
PERFORM CONFIRMATION DRIVING PATTERN Click here

NG

Standard voltage
Alternates between 0.4 V or less and 0.5 V or more.

INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

Disconnect the H12 and H13 heated oxygen sensor connectors.

Measure the resistance of the sensor.

Standard resistance

Bank 1 Sensor 2
Tester Connection	Condition	Specified Condition
1 (HT1B) - 2 (+B)	20°C (68°F)	11 to 16 Ω
1 (HT1B) - 4 (E2)	-	10 kΩ or higher

Bank 2 Sensor 2
Tester Connection	Condition	Specified Condition
1 (HT2B) - 2 (+B)	20°C (68°F)	11 to 16 Ω
1 (HT2B) - 4 (E2)	-	10 kΩ or higher

REPLACE HEATED OXYGEN SENSOR

INSPECT INTEGRATION NO.1 RELAY (MAIN RELAY)

Disconnect the integration relay from the engine room junction block.

Measure the voltage of the MAIN relay.

Standard resistance

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

REPLACE INTEGRATION NO.1 RELAY

CHECK WIRE HARNESS (HEATED OXYGEN SENSOR - ECM)

Disconnect the H12 and H13 connectors.
Disconnect the E15 and E16 ECM connectors.

Measure the resistance of the wire harness side connectors.

Standard resistance

Bank 1 Sensor 2
Tester Connection	Specified Condition
H12-1 (HT1B) - E15-1 (HT1B)	Below 1 Ω
H12-3 (OX1B) - E15-18 (OX1B)	Below 1 Ω
H12-1 (HT1B) or E15-1 (HT1B) - Body ground	10 kΩ or higher
H12-3 (OX1B) or E15-18 (OX1B) - Body ground	10 kΩ or higher

Bank 2 Sensor 2
Tester Connection	Specified Condition
BH13-1 (HT2B) - E16-5 (HT2B)	Below 1 Ω
H13-3 (OX2B) - E16-33 (OX2B)	Below 1 Ω
H13-1 (HT2B) or E16-5 (HT2B) - Body ground	10 kΩ or higher
H13-3 (OX2B) or E16-33 (OX2B) - Body ground	10 kΩ or higher

REPAIR OR REPLACE HARNESS AND CONNECTOR

REPLACE HEATED OXYGEN SENSOR

PERFORM CONFIRMATION DRIVING PATTERN

Tech Tips

Clear all DTCs prior to performing the confirmation driving pattern.

NEXT

READ OUTPUT DTC (DTC P0136 AND/OR P0156 ARE OUTPUT AGAIN)

Connect the intelligent tester to the DLC3.
Turn the ignition switch ON and turn the tester ON.
Enter the following menus: Powertrain / Engine and ECT / DTC.

Read the DTCs.

Result

Display (DTC output)	Proceed to
P0136 and/or P0156 are not output again	A
P0136 and/or P0156 are output again	B

REPLACE HEATED OXYGEN SENSOR

CHECK FOR INTERMITTENT PROBLEMS