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Home >> Subaru >> 2010 >> Legacy Premium, Standard >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 16 (Engine Controls - Engine (Diagnostics) (H6DO - 3.6L DOHC)) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P2099 Post Catalyst Fuel Trim System Too Rich Bank 2 >> Wiring Diagram

DTC P2099 Post Catalyst Fuel Trim System Too Rich Bank 2: Wiring Diagram

WARNING: This page is about a different variant/trim than selected.
Fig 1: HO2S (Bank 1 Sensor 1) - Wiring Diagram
G06648025Courtesy of SUBARU OF AMERICA, INC.
Fig 2: HO2S - Wiring Diagram
G06648028Courtesy of SUBARU OF AMERICA, INC.
DIAGNOSTIC PROCEDURE

Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY.  Is any other DTC displayed? Check DTC using "List of Diagnostic Trouble Code (DTC)". Ref. to LIST OF DIAGNOSTIC TROUBLE CODE (DTC) . Go to step 2  .
2 CHECK FRONT OXYGEN (A/F) SENSOR CONNECTOR AND COUPLING CONNECTOR.  Has water entered the connector? Completely remove any water inside. Go to step 3  .
3 CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connectors from ECM and front oxygen (A/F) sensor.
  3. Measure the resistance of harness between ECM and front oxygen (A/F) sensor connector.

Connector & terminal 
(B135) No. 8 - (E24) No. 3: 
(B135) No. 20 - (E24) No. 4: 		 Is the resistance less than 1 Ω? Go to step 4  . Repair the harness and connector.
NOTE: In this case, repair the following item:
  • Open circuit in harness between ECM and front oxygen (A/F) sensor connector
  • Poor contact of coupling connector
4 CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
Measure the resistance between ECM and chassis ground.
Connector & terminal 
(B135) No. 8-Chassis ground: 
(B135) No. 20 - Chassis ground: 		 Is the resistance 1 MΩ or more? Go to step 5  . Repair the ground short circuit of harness between ECM and front oxygen (A/F) sensor connector.
5 CHECK OUTPUT SIGNAL FOR ECM. 
  1. Connect the connector to ECM.
  2. Turn the ignition switch to ON.
  3. Measure the voltage between front oxygen (A/F) sensor connector and chassis ground.

Connector & terminal 
(E24) No. 3 (+) - Chassis ground (-): 		 Is the voltage 4.5 V or more? Go to step 7  . Go to step 6  .
6 CHECK OUTPUT SIGNAL FOR ECM. 
Measure the voltage between front oxygen (A/F) sensor connector and chassis ground.
Connector & terminal 
(E24) No. 4 (+) - Chassis ground (-): 		 Is the voltage 4.95 V or more? Go to step 7  . Go to step 8  .
7 CHECK OUTPUT SIGNAL FOR ECM. 
Measure the voltage between front oxygen (A/F) sensor connector and chassis ground.
Connector & terminal 
(E24) No. 3 (+) - Chassis ground (-): 
(E24) No. 4 (+) - Chassis ground (-): 		 Is the voltage 8 V or more? Repair the short circuit of harness to power supply between ECM and front oxygen (A/F) sensor connector. After repair, replace the ECM. Ref. to ENGINE CONTROL MODULE (ECM) . Repair the poor contact of ECM connector.
8 CHECK EXHAUST SYSTEM.  Are there holes or loose bolts on exhaust system? Repair the exhaust system. Go to step 9  .
9 CHECK AIR INTAKE SYSTEM.  Are there holes, loose bolts or disconnection of hose on air intake system? Repair the air intake system. Go to step 10  .
10 CHECK FUEL PRESSURE. 
WARNING: Place "NO OPEN FLAMES" signs near the working area.
CAUTION: Be careful not to spill fuel.
  1. Connect the front oxygen (A/F) sensor connector.
  2. Measure the fuel pressure. Ref. to INSPECTION , Fuel Pressure.
CAUTION: Release fuel pressure before removing the fuel pressure gauge.
 Is the measured value 333 - 343 kPa (3.4 - 3.5 kgf/cm2 , 48.4 - 49.8 psi)? Go to step 11  . Repair the following item.
Fuel pressure is too high:
  • Clogged fuel line or bent hose Fuel pressure is too low:
  • Improper fuel pump discharge
  • Clogged fuel line
11 CHECK ENGINE COOLANT TEMPERATURE SENSOR. 
  1. Start the engine and warm up completely.
  2. Read the data of engine coolant temperature sensor signal using Subaru Select Monitor or general scan tool.
NOTE:
  • Subaru Select Monitor For detailed operation procedures, refer to "READ CURRENT DATA FOR ENGINE". Ref. to SUBARU SELECT MONITOR .
  • General scan tool For detailed operation procedures, refer to the general scan tool operation manual.
 Is the temperature 75°C (167°F) or more? Go to step 12  . Replace the engine coolant temperature sensor. Ref. to ENGINE COOLANT TEMPERATURE SENSOR .
12 CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR. 
  1. Start the engine and warm up engine until coolant temperature is higher than 75°C (167°F).
  2. Place the select lever in "P" range or "N" range.
  3. Turn the A/C switch to OFF.
  4. Turn all the accessory switches to OFF.
  5. Read the data of mass air flow and intake air temperature sensor signal using Subaru Select Monitor or general scan tool.
NOTE:
  • Subaru Select Monitor For detailed operation procedures, refer to "READ CURRENT DATA FOR ENGINE". Ref. to SUBARU SELECT MONITOR .
  • General scan tool For detailed operation procedures, refer to the general scan tool operation manual.
 Is the measured value 2.0 - 5.0 g/s (0.26 -0.66 lb/m)? Go to step 13. Replace the mass air flow and intake air temperature sensor. Ref. to MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .
13 CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR. 
  1. Start the engine and warm up engine until coolant temperature is higher than 75°C (167°F).
  2. Place the select lever in "P" range or "N" range.
  3. Turn the A/C switch to OFF.
  4. Turn all the accessory switches to OFF.
  5. Open the front hood.
  6. Measure the ambient temperature.
  7. Read the data of mass air flow and intake air temperature sensor signal using Subaru Select Monitor or general scan tool.
NOTE:
  • Subaru Select Monitor For detailed operation procedures, refer to "READ CURRENT DATA FOR ENGINE". Ref. to SUBARU SELECT MONITOR .
  • General scan tool For detailed operation procedures, refer to the general scan tool operation manual.
 Subtract ambient temperature from intake air temperature. Is the obtained value -10 - 50°C (-18 - 90°F)? Go to step 14  . Check the mass air flow and intake air temperature sensor. Ref. to MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .
14 CHECK REAR OXYGEN SENSOR DATA. 
  1. Warm up the engine until engine coolant temperature is above 75°C (167°F), and keep the engine speed at 3,000 RPM. (2 minutes maximum)
  2. Read the data of rear oxygen sensor signal using Subaru Select Monitor or general scan tool.
NOTE:
  • Subaru Select Monitor For detailed operation procedures, refer to "READ CURRENT DATA FOR ENGINE". Ref. 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 15  . Go to step 16  .
15 CHECK REAR OXYGEN SENSOR DATA. 
  1. Warm up the engine until engine coolant temperature is above 75°C (167°F), and rapidly reduce the engine speed from 3,000 RPM.
  2. Read the data of rear oxygen sensor signal using Subaru Select Monitor or general scan tool.
NOTE:
  • Subaru Select Monitor For detailed operation procedures, refer to "READ CURRENT DATA FOR ENGINE". Ref. 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 17  . Go to step 16  .
16 CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR.  Has water entered the connector? Completely remove any water inside. Go to step 18  .
17 CHECK FRONT OXYGEN (A/F) SENSOR USING REAR OXYGEN SENSOR SIGNAL. 
  1. Warm up the engine until engine coolant temperature is higher than 75°C (167°F), then keep the engine idling for 5 minutes or more.
  2. Read the data of rear oxygen sensor signal using Subaru Select Monitor or general scan tool.
NOTE:
  • Subaru Select Monitor For detailed operation procedures, refer to "READ CURRENT DATA FOR ENGINE". Ref. to SUBARU SELECT MONITOR .
  • General scan tool For detailed operation procedures, refer to the general scan tool operation manual.
 Is a voltage of 0.8 V or more maintained for 5 minutes or more? Replace the front oxygen (A/F) sensor. Ref. to FRONT OXYGEN (A/F) SENSOR . Go to step 18  .
18 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from ECM and rear oxygen sensor.
  3. Measure the resistance of harness between ECM and rear oxygen sensor connector.

Connector & terminal 
(B135) No. 28 - (E25) No. 3: 
(B135) No. 30 - (E25) No. 4: 		 Is the resistance less than 1 Ω? Go to step 19  . 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
19 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. 
  1. Connect the connector to ECM.
  2. Turn the ignition switch to ON.
  3. Measure the voltage between rear oxygen sensor connector and chassis ground.

Connector & terminal 
(E25) No. 3 (+) - Chassis ground (-): 		 Is the voltage 0.2 - 0.5 V? Replace the rear oxygen sensor. Ref. to REAR OXYGEN SENSOR . 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 ECM connector
  • Poor contact of coupling connector
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