1 CHECK REAR OXYGEN SENSOR DATA.
- Warm up the engine until engine coolant temperature is above 75°C (167°F), and keep the engine speed at 3,000 RPM. (for up to 2 minutes)
- Read the data of rear oxygen sensor signal using Subaru Select Monitor or general scan tool.
NOTE:
- SUBARU SELECT MONITOR
For detailed operation procedure, refer to
SUBARU SELECT MONITOR .
- General Scan Tool
For detailed operation procedures, refer to the general scan tool operation manual.
|
Is the voltage 490 mV or more? |
Go to step 6. |
Go to step 2. |
2 CHECK REAR OXYGEN SENSOR DATA.
- Warm up the engine until engine coolant temperature is above 75°C (167°F), and rapidly reduce the engine speed from 3,000 RPM.
- Read the data of rear oxygen sensor signal using Subaru Select Monitor or general scan tool.
NOTE:
- SUBARU SELECT MONITOR
For detailed operation procedure, refer to
SUBARU SELECT MONITOR .
- General Scan Tool
For detailed operation procedures, refer to the general scan tool operation manual.
|
Is the voltage 250 mV or less? |
Go to step 6. |
Go to step 3. |
| 3 CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR. |
Has water entered the connector? |
Completely remove any water inside. |
Go to step 4. |
4 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR.
- Turn the ignition switch to OFF.
- Disconnect the connectors from ECM and rear oxygen sensor.
- Measure the resistance of harness between ECM and rear oxygen sensor connector.
Connector & terminal
(B135) No. 4 - (E23) No. 3:
(B134) No. 29 - (E23) No. 4:
|
Is the resistance less than 1 Ω? |
Go to step 5. |
Repair the harness and connector.
NOTE:
In this case, repair the following item:
- Open circuit in harness between ECM and rear oxygen sensor connector
- Poor contact of coupling connector
|
5 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR.
- Turn the ignition switch to OFF.
- Disconnect the connector from rear oxygen sensor.
- Turn the ignition switch to ON.
- Measure the voltage between rear oxygen sensor connector and chassis ground.
Connector & terminal
(E23) No. 3 (+) - Chassis ground (-):
|
Is the voltage 0.2 - 0.5 V? |
Replace the rear oxygen sensor. Refer to
REAR OXYGEN SENSOR
. |
Repair the harness and connector.
NOTE:
In this case, repair the following item:
- Open circuit of harness between the ECM and rear oxygen sensor
- Poor contact of the rear oxygen sensor connector
- Poor contact in ECM connector
|
6 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following items.
- Looseness and improper attachment of exhaust system parts
- Damage (crack, hole etc.) of parts
- Looseness and improper attachment of parts between front oxygen (A/F) sensor and rear oxygen sensor
|
Is there any fault in exhaust system? |
Repair or replace faulty parts. |
Replace the rear oxygen sensor. Refer to
REAR OXYGEN SENSOR
. |