Diagnostics

6-1. NA Engine (Diagnosis)

1. Overview

A: Reference

The on-board diagnostic (OBD) system detects and indicates malfunctions in the inputs and outputs of complex electronic controls. The engine warning light on the instrument panel alerts the driver of any malfunctions or breakdowns.

In addition, a fail-safe function is installed to ensure a minimum level of driving performance in the event that the vehicle is unable to drive due to sensor failure.
The OBD system installed in vehicles with this type of engine complies with JOBD regulations. The OBD system monitors for failures of the components and systems described in the “Engine section” that affect emissions.
When the system detects a malfunction, the engine warning light comes on. At the same time that the engine warning light comes on or flashes, the (DTC) table and engine freeze frame status are stored in the on-board computer.
When the OBD system detects a malfunction, it stores engine status data (engine load, engine coolant temperature, fuel trim, engine RPM, vehicle speed, etc.) in the freeze frame in the on-board computer.

The stored freeze frame engine status data will be maintained until the (DTC) table is cleared, but the freeze frame

● If a fuel trim or misfire malfunction is detected while the engine status data in the frame is being maintained, it will be overwritten with the engine status data 4 in the freeze frame related to fuel trim or misfire.

If the malfunction does not occur again within three consecutive drive cycles, the engine warning light will go off but the (DTC) table will remain in the on-board computer.

When diagnosing vehicle malfunctions, connect the Subaru Select Monitor to the vehicle.

B: Preparation Tools

Illustration	Tool Number	Name	Use
	1B02XJ0	Subaru Select Monitor III Kit	Used to diagnose electrical system faults.

2. Engine Control Unit (ECU) I/O Signals

A. Specifications (Electrical Equipment)

Name	Connector Number	Terminal Number	Signal (V)		Reference
			Ignition switch ON (engine OFF)	Engine ON (idling)
Main power supply 1	R134	2	10 ~ 30	13 ~ 15
Main power supply 2 TA	R134	1	10 ~ 13	13 ~ 15
Backup power supply	R134	8	10 ~ 13	13 ~ 15
Sensor system power supply	R135	18	5	5
IG SW	R134	4	10 ~ 13	13 ~ 15
Crank angle sensor	R135	16	~ 5	See input/output waveform diagram
Cam angle sensor	R135	6	~ 5	See input/output waveform diagram
Throttle opening	R135	3	Fully close: 0.5 Fully open: 4.3	0.5 (Throttle fully closed)	See also characteristic graph
Knock sensor	R135	23	See input/output waveform diagram
Knock sensor shield	R135	24	Always approx. 0
Front O2 sensor	R135	14	0 ~ 1.0	See input/output waveform diagram
Front O2 sensor shield	R135	26	Always approx. 0
Rear O2 sensor	R133	16	0 ~ 1.0	See input/output waveform diagram
Rear O2 sensor shield	R133	17	Always approx. 0
Pressure sensor signal	R135	4	~ 4.3		See also characteristic graph
Water temperature sensor	R135	5	About 40°C (about 2.0) About 60°C (about 1.2) About 80°C (about 0.8)		See also characteristic graph
A/C thermo signal	R134	6
Intake air temperature sensor	R135	15	About 20°C (about 3.0) About 40°C (about 2.0) About 60°C (about 1.3)		See also characteristic graph
Engine room remperature sensor	R133	26	About 20°C (about 3.6) About 40°C (about 2.8) About 60°C (about 2.0)
Rear defogger	R134	21	When SW is OFF: 0 SWON: 10~15
Small light	R134	13	When SW is OFF: 0 SWON: 10~15
Power steering signal	R133	13	When turning (signal ON): 0 Going straight (signal OFF): 10~15
Heater proa	R134	11	When SW is OFF: 10 to 15 SWON: 2 or less
A/C signal	R134	3	SWON: 10~15 When SW is off: 0
Vehicle speed sensor	R133	24	Refer to input/output waveform diagram.		MT Model
Vehicle speed sensor (+)	R133	21	Refer to input/output waveform diagram.		AT Model
Vehicle speed sensor (-)	R133	10	Refer to input/output waveform diagram.		AT Model
Vehicle speed sensor shield	R133	11	Always approx. 0		AT Model
Vehicle speed sensor	R133	12	Refer to input/output waveform diagram.		AT Model
Plake SW	R134	18	Brake pedal depressed: 10~15 Brake pedal released: 0
Power mode SW	R134	20	During SWON: 0 When SW is OFF: 10~15		AT model
P range	R133	7	P range: 10~15 Other than P range: 0		AT model
R range	R133	18	R range: 10~15 Other than R range: 0		AT model
N range	R133	8	N range: 10~15 Other than N range: 0		AT model
D range	R133	19	D range: 10~15 Other than D range: 0		AT model
2 ranges	R133	9	2 range: 10~15 Other than 2 ranges: 0		AT model
1 range	R133	20	1 range: 10~15 Other than 1 range: 0		AT model
Test terminal	R134	19	Terminal release: 10~15 When terminal is connected: 0
Ignition output #1	R135	10	About 0	See input/output waveform diagram
Ignition output #2	R135	9	About 0	See input/output waveform diagram
Injector #1	R135	20	10~13	See input/output waveform diagram
Injector #2	R135	19	10~13	See input/output waveform diagram
Injector #3	R135	28	10~13	See input/output waveform diagram
Injector #4	R135	27	10~13	See input/output waveform diagram
Alternator	R133	23	When stopped (not in operation): 5.0~8.5 When activated: 0 and 5.0~8.5 (duty)		Period 50ms
Select monitor	R134	9	About 10~15
ABS idle up signal	R133	14	10~13	13~15
ISC #1	R135	22	0 or 10 to 13	0 and 13~15 (pulse)	See input/output waveform diagram
ISC #2	R135	21	0 or 10 to 13	0 and 13~15 (pulse)	See input/output waveform diagram
ISC #3	R135	30	0 or 10 to 13	0 and 13~15 (pulse)	See input/output waveform diagram
ISC #4	R135	29	0 or 10 to 13	0 and 13~15 (pulse)	See input/output waveform diagram
Engine room fan relay	R134	14	Non-operating: 10~15 When in operation approx. 0
Powertrain warning light	R134	22	0	When lights are off: 10~15 Wheb lit: 0
Sub fan relay	R134	24	Non-operating: 10~15 When in operation approx. 0
Radiator fan relay	R134	15	Non-operating: 10~15 When in operation approx. 0
A/C compressor Control	R134	16	Non-operating: 10~15 When in operation approx. 0
Fuel pump relay	R134	23	When stopped (not operating): 10~15 When in operation approx. 0	About 0
Tachometer output	R133	15	10~13	0 and 10-14 (duty)
Self shut off	R134	10	Below 1V
CPC solenoid	R135	8	10~13	See input/output waveform diagram
Front O2 sensor heater	R133	5	10~13	See input/output waveform diagram
Rear O2 sensor heater	R133	6	10~13	See input/output waveform diagram
Shift solenoid 1	R133	2	1st gear: 10~15 2nd gear: 10~15 3rd gear: 0		AT model
Shift solenoid 2	R133	1	1st gear: 10~15 2nd gear: 10~15 3rd gear: 0		AT model
Sensor ground 1	R135	7	Always approx. 0
Sensor ground 2	R135	17	Always approx. 0
Sensor ground (rear O2 sensor)	R133	25	Always approx. 0
Sensor ground (body)	R134	5	Always approx. 0
Power ground	R133	3	Always approx. 0
Power ground	R133	4	Always approx. 0
Control system ground	R135	1	Always approx. 0
Control system ground	R135	2	Always approx. 0

Engine

3. Inspection mode

A: Carry out the diagnosis shown in the following diagnostic code (DTC) table.

When performing a diagnosis that is not shown in the diagnostic code (DTC) table, refer to the drive cycle section. (See 6-12 “Drive Cycle”.)

DTC	Category	Category
P0031	O2 Sensor Heater Circuit (LOW) (Bank 1 Sensor 1)
P0032	O2 Sensor Heater Circuit (HIGH) (Bank 1 Sensor 1)
P0037	O2 Sensor Heater Circuit (LOW) (Bank 1 Sensor 2)
P0038	O2 Sensor Heater Circuit (HIGH) (Bank 1 Sensor 2)
P0107	Intake pressure sensor circuit (LOW)
P0108	Intake pressure sensor circuit (HIGH)
P0112	Intake air temperature sensor circuit (LOW)
P0113	Intake air temperature sensor circuit (HIGH)
P0117	Water temperature sensor circuit (LOW)
P0118	Water temperature sensor circuit (HIGH)
P0122	Throttle position sensor A circuit (LOW)
P0122	Throttle position sensor A circuit (HIGH)
P0130	O2 sensor circuit (Bank 1 Sensor 1)
P0136	O2 sensor circuit (Bank 1 Sensor 2)
P0327	Knock sensor 1 circuit (LOW)
P0328	Knock sensor 1 circuit (HIGH)
P0335	Crank angle sensor A system circuit
P0340	Cam angle sensor A system circuit 1
P0350	Ignition coil system circuit
P0444	Canister purge solenoid circuit (LOW)
P0445	Canister purge solenoid circuit (HIGH)
P0500	Vehicle speed sensor system
P0562	Charging circuit (LOW)
P0562	Charging circuit (HIGH)
P0705	AT Range SW circuit
P0720	AT vehicle speed sensor circuit
P0753	AT shift solenoid 1 circuit (shift solenoid A)
P0758	AT shift solenoid 2 circuit (shift solenoid B)
P0790	Mode SW circuit
P1510	ISC signal line 1 circuit (LOW)
P1511	ISC signal line 1 circuit (HIGH)
P1512	ISC signal line 2 circuit (LOW)
P1513	ISC signal line 2 circuit (HIGH)
P1514	ISC signal line 3 circuit (LOW)
P1515	ISC signal line 3 circuit (HIGH)
P1516	ISC signal line 4 circuit (LOW)
P1517	ISC signal line 4 circuit (HIGH)
P1521	Brake signal circuit
P1522	Electrical load signal system circuit
P1525	Blower fan circuit
P1559	Intake system
P1560	Backup power supply

Preparation for Inspection
1. Make sure there is about half a fuel tank [10~20 liters (2.7~5.3 US gal, 2.2~ 4.4 Imp gal)] remaining and the battery voltage is 12 V or higher.
2. Use a garage jack to jack up the vehicle and place it on a rigid rack or run the vehicle on free rollers.

Warning:

Before jacking up the vehicle, make sure the parking brake is on.
Do not use a pantograph jack instead of a rigid rack.
Attach a rope or wire to the front or rear towing hook to prevent the front wheel from swaying sideways.
Before you spin the wheels, make sure there is no one in front of the vehicle, and keep no one in front of the vehicle while you are spinning the wheels.
Make sure there are no obstacles near the wheels, especially all four wheels if you have an AWD model.
While working, do not suddenly press or release the clutch pedal or accelerator pedal, regardless of the engine speed. Sudden operation may cause the vehicle to separate from the free rollers.
To prevent the vehicle from slipping due to vibration, do not place anything between the rigid rack and the vehicle.

Subaru Select Monitor
1. After clearing the memory, check that no unsolved fault data remains. (See 6-13 “Clear Memory Mode”.)
2. Warm up the engine.
3. Prepare the Subaru Select Monitor Kit. 6-2 “Overview and Preparation Tools.”
4. Prepare a computer with the Spartan Select Monitor installed.
5. Connect the USB cable to the SDI (Subaru Diagnostic Interface) and the computer’s USB port (Subaru Select Monitor dedicated port).
  Reference:
  - The Subaru Select Monitor dedicated port refers to the USB port used when installing the Subaru Select Monitor.
6. Connect the diagnostic cable to SDI.
7. Connect the test mode connector (A) located at the bottom of the instrument panel (driver’s side).
8. Connect the SDI to the data link connector installed at the bottom of the instrument panel (driver’s seat side).
  
  Notice: Do not connect any scan tools other than the Subaru Select Monitor.
9. Start your computer.
10. Turn the ignition switch ON (engine OFF) and launch the “Subaru Select Monitor PC Application.”
11. On the main menu screen, select “Individual System Check.”
12. On the «System Selection Menu» screen, select {Engine}.
13. After the engine type information is displayed, click the [OK] button.
14. On the “Engine Fault Diagnosis” screen, select “D Check.”
15. When the message “Do you want to perform a D check?” appears on the screen, click the [Next] button.
16. Follow the next steps as instructed on the screen.
  Reference:
  - If a malfunction remains in the memory, the corresponding DTC will be displayed on the screen.
  - For detailed operating procedures, refer to the “Subaru Select Monitor PC Application Help.”
  - For details on the DTC, refer to the diagnostic code (DTC) table. (See Diagnostics Code (DTC) table on page 6-14.)
  - If the speed difference between the front and rear wheels occurs, the ABS warning light may come on, but this is not a malfunction. After the engine control diagnosis is complete, perform the ABS memory clear procedure in the self-diagnosis function.

4. Drive cycle

A: Procedure

The drive patterns shown below are used to diagnose malfunctions. By implementing the specified drive patterns, the malfunctions listed below can be diagnosed. After repairing the malfunctions listed below, be sure to implement the required drive pattern and check that the function has been restored correctly.

Preparing the Drive Cycle
1. Make sure there is about half a tank of fuel [10~20 liters (2.7~5.3 US gal, 2.2~4.4 Imp gal)] remaining and the battery voltage is 12V or higher.
2. Disconnect the test mode connector.
  
  Reference:
  - Unless the engine coolant temperature is specified at start-up, always perform the diagnosis after the engine has warmed up.
  - If the DTC has an * mark, perform the diagnosis twice. After the first diagnosis is completed, stop the engine and perform the second diagnosis under the same conditions.
Drive cycle 1 (Drive for 20 minutes at 55-65 km/h, then idle the engine for 3 minutes.)

Reference:
- If it is not possible to drive continuously for 20 minutes, drive the vehicle while meeting the following conditions 4 to 5 times without turning off the engine.
- Each run lasts approximately 5 minutes.
- Drive at a constant speed (55-65km/h).
- Reduce acceleration and deceleration (throttle operation) while driving at a constant speed.

DTC	Project	Condition
*P0133	O2 Sensor response (Bank 1 Sensor 1)
*P0139	O2 Sensor response (Bank 1 Sensor 2)
*P0171	Fuel System 1 (Lean)
*P0172	Fuel System 1 (Rich)
*P0301	#1 Cylinder misfire
*P0302	#2 Cylinder misfire
*P0303	#3 Cylinder misfire
*P0304	#4 Cylinder misfire
*P0420	Catalyst system

5. Clear Memory Mode

A: Operation

On the main menu screen, select “Individual System Check.”
On the «System Selection Menu» screen, select {Engine}.
After the engine type information is displayed, click the [OK] button.
On the ENGINE DIAGNOSIS screen, select MEMORY CLEAR.
When the message “Do you want to clear memory?” appears on the screen, click the [Yes] button.
When “Executed” and “Turn IG SW OFF” are displayed on the screen, turn the ignition switch OFF.

Reference:
- For detailed operating procedures, refer to the “Subaru Select Monitor PC Application Help.”

6. Diagnostic Code (DTC) List

A: List

DTC	Project	Reference
P0037	O2 Sensor Heater Circuit (LOW) (Tire 1 Sensor 2)	(See 6-15 "Diagnostic Procedures Using Diagnostic Codes (DTCs)", DTC P0037 (See "O2 Sensor Heater Circuit (LOW) (Bank 1 Sensor 2)"
P0038	O2 Sensor Heater Circuit (HIGH) (Bank 1 Sensor 2)	(See 6-17 "Diagnostic Procedures Using Diagnostic Codes (DTCs)", DTC P0038 (See "O2 Sensor Heater Circuit (HIGH) (Bank 1 Sensor 2)"
P0136	O2 Sensor Circuit (Bank 1 Sensor 2)	6-19 "Diagnostic Procedures Using Diagnostic Codes (DTCs) DTC P0136 (See "O2 Sensor Circuit (Bank 1 Sensor 2)"
P0139	O2 Sensor Response (Bank 1 Sensor 2)	(See 6-22 "Diagnostic Procedures Using Diagnostic Codes (DTCs)," DTC P0139 (See "O2 Sensor Response (Bank 1 Sensor 2)"
P0420	Catalyst system	(See 6-24 "Diagnostic Procedures Using Diagnostic Codes (DTCs)," DTC P0420 (See "Catalyst Systems.")

7. Diagnostic Procedures When Using Diagnostic Codes (DTC)

A: DTC P0037 O2 Sensor Heater Circuit (LOW) (Bank 1 Sensor 2)

Notice: After repairing or replacing the defective parts, execute the clear memory mode (see “Clear Memory Mode, Operation” on page 6-13) and the inspection mode (see “Inspection Mode, Procedure” on page 6-9).

Wiring diagram:

Step	Check	Yes	No
Step 1. Check the power supply to the rear 2 sensors 1. Turn the ignition switch OFF. 2. Disconnect the connector from the rear O2 sensor. 3. Turn the ignition switch ON. 4. Between the rear O2 sensor connector and body ground measure voltage. Connectors & terminals: (R114) No.2 (+) - Body Earth (-)	Is the voltage 10V or more?	Proceed to step 2.	Repair the power supply line.
Step 2. Check the harness between the ECU and the rear O2 sensor Measure the resistance between the ECU connector and the Rear O2 sensor connector. Connectors & terminals: (R133) No. 6 - (R114) No. 4	Is the resistance less than 1MΩ?	Proceed to step 3.	Repair the break in the harness between the ECU and the rear O2 sensor.
Step 3. Check the ECU earth circuit 1. Turn the ignition switch OFF. 2. Disconnect the connector from the ECU. 3. Check the harness between the ECU connector and the body ground. Measure resistance. Connectors & terminals: (R133) No. 3 - Body Earth (R133) No. 4 - Body Earth (R135) No. 1 - Body Earth (R135) No. 2 - Body Earth	Is the resistance below 52?	Proceed to step 4.	Repair the break in the hardness between the ECU and the body ground.
Step 4. Check the rear 2 sensors 1. Turn the ignition switch OFF. 2. Measure the resistance between the rear O2 sensor connector terminals. Terminals: No. 1 - No.2	Is the resistance 3.0~4.02?	Repair the poor contact of the ECU connector.	Rear O2 sensor exchange.

B: DTC P0038 O2 Sensor Heater Circuit (HIGH) (Bank 1 Sensor 2)

Notice: After repairing or replacing the defective parts, execute the clear memory mode (see “Clear Memory Mode, Operation” on page 6-13) and the inspection mode (see “Inspection Mode, Procedure” on page 6-9).

Wiring diagram:

Step	Check	Yes	No
Step 1. Check the harness between the ECU and the rear O2 sensor 1. Turn the ignition switch OFF. 2. Disconnect the connector from the rear O2 sensor. 3. Measure the voltage between the ECU and body ground. Connectors & Terminals: (R133) No. 6 (+) - Body Earth (-)	Is the voltage 10V or higher?	Repair the power short in the harness between the ECU and the rear O2 sensor connector.	Proceed to step 2.
Step 2. Check the ECU earth circuit 1. Disconnect the connector from the ECU. 2. Measure the resistance of the harness between the ECU connector and body ground. Connectors & Terminals: (R133) No. 3 - Body Earth (R133) No. 4 - Body Earth (R135) No. 1 - Body Earth (R135) No. 2 - Body Earth	Is the resistance below 52?	Repair the poor contact of the ECU connector. If there is a problem, replace the ECU.	Repair the break in the harness between the ECU connector and the body ground.

C: DTC P0136 O2 Sensor Circuit (Bank 1 Sensor 2)

Notice: After repairing or replacing the defective parts, execute the clear memory mode (see “Clear Memory Mode, Operation” on page 6-13) and the inspection mode (see “Inspection Mode, Procedure” on page 6-9).

Wiring diagram:

Step	Check	Yes	No
Step 1. Check the screen for other DTCs.	Are any other DTCs showing up?	Check the DTCs using the "Diagnostic Code (DTC) Table". (See "Diagnostic Code (DTC) Table" on page 6-14.)	Go to Step 2.
Step 2. Checking rear 2 sensor data 1. Warm up the engine until the engine coolant temperature exceeds 70°C (158°F), then maintain the engine speed between 2,000 rpm and 3,000 rpm for two minutes. 2. Use the Subaru Select Monitor to read the rear O2 sensor signal data.	Is the voltage below 1.0V?	Proceed to Step 3.	Proceed to Step 8.
Step 3. Check the harness between the ECU and the rear O2 sensor connector. 1. Turn the ignition switch ON. 2. Measure the voltage between the ECU connector and body ground. Connectors & Terminals: (R133) No. 16 (+) - Body Earth (-)	Is the voltage 10V or higher?	Repair the power short in the harness between the ECU and the rear O2 sensor connector.	Proceed to Step 4.
Step 4. Harness between ECU and rear O2 sensor connector: Inspection 1. Turn the ignition switch OFF. 2. Disconnect the connector from the ECU and the rear O2 sensor. 3. Measure the resistance between the rear O2 sensor connector and body ground. Connectors & Terminals: (R114) No. 3 - Body Earth	Is the resistance greater than 1MΩ?	Proceed to Step 5.	Repair the ground short in the harness between the ECU and the rear O2 sensor connector.
Step 5. Check the rear 2 sensor data 1. Connect all connectors. 2. Idle the engine. 3. Idle the engineUse the Subaru Select Monitor to check the rear O2 sensor. Read the data of the sensor signal.	Is the voltage 0.7 to 0.09V?	Proceed to Step 6.	Replace the rear O2 sensor.
Step 6. Harness between ECU and rear O2 sensor connector: Inspection: 1. Turn the ignition switch OFF. 2. Disconnect the connectors from the ECU and the rear O2 sensor. 3. Measure the resistance of the harness between the ECU and the rear O2 sensor connector. Connectors & Terminals: (R133) No. 16 - (R114) No.3	Resistance less than 1MΩ?	Proceed to Step 7.	Repair the open circuit in the harness between the ECU and the rear O2 sensor connector.
Step 7. Harness between rear O2 sensor and ECU connector Inspection: 1. Connect the connector to the ECU and rear O2 sensor.. 2. Turn the ignition switch ON. 3. Replace the rear O2 sensor harness connector and tighten the ground terminal. Connectors & Terminals: (R114) No. 3 (+) - Body Earth (-)	Is the voltage less than 0.2V?	Repair poor contact in the rear O2 sensor connector and ECU connector.	Replace the rear O2 sensor.
Step 8. Engine System Inspection Inspect the exhaust system components. Reference: Check the following items: - Loose and incompletely installed exhaust system parts - Damage to parts (cracks, holes, etc.) - Parts between the front O2 sensor and the reas O2 sensor - Loose and incomplete installation	Is there a problem with the exhaust system?	Repair or replace defective parts.	Replace the rear O2 sensor.

D: DTC P0139 O2 Sensor Response (Bank 1 Sensor 2)

Notice: After repairing or replacing the defective parts, execute the clear memory mode (see “Clear Memory Mode, Operation” on page 6-13) and the inspection mode (see “Inspection Mode, Procedure” on page 6-9).

Wiring diagram:

Step	Check	Yes	No
Step 1. Inspection: 1. Turn the ignition switch OFF. 2. Disconnect the connectors from the ECU and rear O2 sensor.. 3. Measure the resistance of the harness between the ECU and the rear O2 sensor connector. Connectors & Terminals: (R133) No. 16 - (R114) No. 3	Resistance less than 1MΩ?	Proceed to Step 2.	Repair the break in the harness between the power connectors.
Step 2. Harness between ECU and rear O2 sensor connector Inspection: Measure the resistance between the rear O2 sensor connector and body ground. Connectors & Terminals: (R114) No. 3 - Body Earth	Is the resistance greater than 1MΩ?	Proceed to Step 3.	Repair the short to earth in the harness between the power connectors.
Step 3. Check the rear 2 sensors Measure the resistance between the rear O2 sensor terminals.. Terminals: No. 3 - No. 1	Is the resistance less than 1MΩ?	Rear O2 sensor exchange	Even if the powertrain warning light comes on, the circuit has returned to normal at this point. Recreate the fault and perform the diagnosis again. Reference: In this case, a temporary connector contact failure may be the cause.

E: DTC P0420 Catalyst system

Notice: After repairing or replacing the defective parts, execute the clear memory mode (see “Clear Memory Mode, Operation” on page 6-13) and the inspection mode (see “Inspection Mode, Procedure” on page 6-9).

Wiring diagram:

Step	Check	Yes	No
Step 1. Inspecting the exhaust system Check for gas leaks or air inhalation caused by loose or missing nuts and bolts, and for holes in the exhaust pipe. Reference: Check the following locations. - Between the cylinder head and the front exhaust pipe - Between the front exhaust pipe and the front catalyst - Between the front and rear catalysts - The front O2 sensor or rear O2 sensor is loose or incompletely installed.	Is there a problem with the exhaust system?	Repair or replace the exhaust system	Proceed to Step 2.
Step 2. Checking the waveform data on the Subaru Select Monitor (while driving) 1. Drive at a constant speed of 55-66km/h. 2. After 5 minutes have elapsed in the state of Step 1), use the Subaru Select Monitor to read the waveform data while the vehicle is still driving. - Normal: - When abnormal (many inversions)	Is the normal waveform displayed?	Even if the powertrain warning light comes on, the circuit has returned to normal at this point. Recreate the fault and perform the diagnosis again. Reference: In this case, a temporary connector contact failure is suspected.	Proceed to Step 3.
Step 3. Checking the waveform data on the Subaru Select Monitor (while idling) 1. Idle the vehicle. 2. While in Step 1), use the Subaru Select Monitor to read the waveform data. - Normal: - Abnormality 1 (many inversions) - Abnormality 2 (noise mixed)	Is the normal waveform displayed?	Proceed to Step 4.	- If the waveform of abnormality 1 is displayed: Go to Step 4. - If the waveform of abnormality 2 is displayed, proceed to Step 5.
Step 4. Inspecting the catalyst	Is there damage to the catalyst?	Replace the catalyst	Proceed to Step 5.
Step 5. Check the rear 2 sensor connector and intermediate connector	Has water gotten into the connector?	Completely prevent water ingress.	Proceed to Step 6.
Step 6. Harness between ECU and rear O2 sensor connector Inspection: 1. Turn the ignition switch OFF. 2. Disconnect the connectors from the ECU and rear O2 sensor. 3. Measure the resistance of the harness between the ECU and the rear O2 sensor connector. Connectors & Terminals: (R133) No. 16 - (R114) No. 3 (R133) No. 25 - (R114) No. 1	Resistance less than 1MΩ?	Proceed to Step 7.	Repair the harness and connectors. Reference: Repair the following locations: - Disconnection in the harness between the ECU and the rear O2 sensor connector. - Poor contact at the short connector.
Step 7. Harness between ECU and rear O2 sensor connector Inspection: 1. Connect the connector to the ECU. 2. Turn the ignition switch ON. 3. Measure the voltage between the rear O2 sensor connector and body ground. Connectors & Terminals: (R114) No. 3 (+) - Body Earth (-)	Is the voltage 0.2 to 0.5V?	Proceed to Step 8.	Repair the harness and connector. Reference: Repair the following locations: - Open circuit between ECU and rear O2 sensor - Poor contact of the ECU connector
Step 8. Check the rear 2 sensor shield 1. Turn the ignition switch OFF. 2. Expose the sensor shield on the body side harness of the rear O2 sensor connector. 3. Measure the resistance between the sensor shield and body ground.	Is the resistance less than 1MΩ?	Replace the rear O2 sensor.	Repair the disconnection in the rear O2 sensor heater circuit.

6-2. SC Engine (Diagnosis)

1. Clear memory mode

A: Operation

On the main menu screen, select “Individual System Check.”
On the «System Selection Menu» screen, select {Engine}.
After the engine type information is displayed, click the [OK] button.
On the screen, select {Memory Clear}.
When the message “Do you want to clear memory?” appears on the screen, click the [Yes] button.
When “Executed” and “Turn IG SW OFF” are displayed on the screen, turn the ignition switch OFF.

Reference:
- For detailed operating procedures, refer to the “Subaru Select Monitor PC Application Help.”

2. Diagnostic Code (DTC) List

A: List

DTC	Project	Reference
P0136	O2 Sensor Circuit (Bank 1 Sensor 2)	(See "Diagnostic Procedure When Using Diagnostic Code (DTC) DTC P0136 02 Sensor System Circuit (Bank 1 Sensor 2)" on page 6-30.)
P0136	O2 Sensor Circuit (Bank 1 Sensor 2)	(See "Diagnostic Procedure When Using Diagnostic Code (DTC) DTC P0136 02 Sensor System Circuit (Bank 1 Sensor 2)" on page 6-30.)

3. Diagnostic procedure when using diagnostic codes (DTC)

A: DTC P0136 O2 Sensor Circuit (Bank 1 Sensor 2)

Notice: After repairing or replacing the defective parts, execute the clear memory mode (see “Clear Memory Mode, Operation” on page 6-28).

Wiring diagram:

</tr> </table>

Step	Check	Yes	No
Step 1. Check the screen for any other DTCs	Are there any other DTCs showing up?	Check the DTCs using the "Diagnostic Code (DTC) Table." (See "Diagnostic Code (DTC) Table" on page 6-29.)	Proceed to Step 2.
Step 2. Checking the rear 2 sensor data	Is the voltage below 1.0V?	Proceed to Step 3.	Proceed to Step 8.
Step 3. Harness between ECU and rear O2 sensor connector Inspection 1. Turn the ignition switch ON. 2. Measure the voltage between the ECU connector and body ground. Connectors & terminals (R134) No. 12 (+) - Body Earth (-)	Is the voltage 10V or higher?	Repair the power short in the harness between the ECU and the rear O2 sensor connector.	Proceed to Step 4.
Step 4. Harness between ECU and rear O2 sensor connector Inspection 1. Turn the ignition switch OFF. 2. Disconnect the connectors from the ECU and the rear O2 sensor. 3. Measure the resistance between the rear O2 sensor connector and body ground. Connectors & terminals (R114) No. 1 - Body Earth	Is the resistance greater than 1MΩ?	Proceed to Step 5.	Repair the ground short in the harness between the ECU and the rear O2 sensor connector.
Step 5. Checking rear 2 sensor data 1. Connect all connectors. 2. Start the engine and let it idle. 3. Use the Subaru Select Monitor to read the rear ○₂ sensor signal data.	Is the voltage 0.7 to 0.9V?	Proceed to 6.	Replace the rear 2 sensors.
Step 6. Harness between ECU and rear O2 sensor connector Inspection 1. Turn the ignition switch OFF. 2. Disconnect the connectors from the ECU and the rear O2 sensor. 3. Measure the resistance between the ECU and the rear O2 sensor connector. Connectors & terminals (R134) No. 12 - (R114) No. 1)	Is the resistance less than 1MΩ?	Proceed to Step 7.	Repair the open circuit in the harness between the ECU and the rear O2 sensor connector.
Step 7. Harness between ECU and rear 2 sensor connector Inspection 1. Connect the connector to the ECU and rear O2 sensor. 2. Turn the ignition switch ON. 3. Measure the voltage between the rear O2 sensor harness connector and body ground. Connectors & terminals (R114) No. 1 (+) - Body Earth (-)	Is the voltage less than 0.2V?	Repair the poor contact of the rear O2 sensor connector and the ECU connector.	Replace the rear O2 sensor.
Step 8. Inspecting the exhaust system Inspect the exhaust system components. Reference: Check the following items: - Loose and incompletely installed exhaust system parts. - Damage to parts (cracks, holes, etc.) - Loose or incomplete installation of parts between the front O2 sensor and rear O2 sensor	Is there a problem with the exhaust system?	Repair or replace defective parts./td>	Replace the rear O2 sensor.