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DTC P2099 Post Catalyst Fuel Trim System Too Rich Bank 2

WARNING: This page is about a different car, the 2006 Subaru Outback. However, it is still accessible from the selected car via links, so may be relevant.

DTC DETECTING CONDITION: 

CAUTION: After repair or replacement of faulty parts, perform Clear Memory Mode < Ref. to OPERATION , Clear Memory Mode. > and Inspection Mode < Ref. to PROCEDURE , Inspection Mode. >.

WIRING DIAGRAM: 

Fig 1: Front Oxygen (A/F) Sensor - Wiring Diagram
G05019027
Fig 2: Rear Oxygen Sensor - Wiring Diagram
G05019030
DTC P2099 POST CATALYST FUEL TRIM SYSTEM TOO RICH BANK 2 - DIAGNOSTIC PROCEDURE

Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY.  Is any other DTC displayed? Inspect the relevant 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 DATA. 
  1. Start the engine.
  2. While observing the Subaru Select Monitor or general scan tool screen, warm-up the engine until engine coolant temperature is above 75°C(167°F). If the engine is already warmed-up, operate at idle speed for at least 1 minute.
  3. Read data of front oxygen (A/F) sensor signal using the Subaru Select Monitor or general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedure, 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 Instruction Manual".

 Is the measured value within 0.86 -1.15 at idle? Go to step 3.  Go to step 4  .
3 CHECK REAR OXYGEN SENSOR SIGNAL. 
  1. Race engine at speeds from idling to 5,000 rpm for a total of 5 cycles.
    NOTE: To increase engine speed to 5,000 rpm, slowly depress accelerator pedal, taking approximately 5 seconds, and quickly release accelerator pedal to decrease engine speed.
  2. Operate the LED operation mode for engine.
NOTE: Subaru Select Monitor
For detailed operation procedure, refer to the "LED OPERATION MODE FOR ENGINE" < Ref. to SUBARU SELECT MONITOR . >
 Does the LED of {Rear O2 Rich Signal} blink? Check front oxygen (A/F) sensor circuit. Check rear oxygen sensor circuit. < Ref. to REAR OXYGEN SENSOR . >
4 CHECK EXHAUST SYSTEM. 
Check exhaust system parts.
NOTE: Check the following items.
  • Looseness of part installation
  • Damage (crack, hole etc.) of parts
  • Looseness of the front oxygen (A/F) sensor
  • Looseness or ill fitting of parts between from oxygen (A/F) sensor and rear oxygen sensor
 Is there any fault in exhaust system? Repair or replace faulty parts. Go to step 5  .
5 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 6  .
6 CHECK FUEL PRESSURE. 
WARNING:
  • Place "NO FIRE" signs near the working area.
  • Be careful not to spill fuel.

Measure the fuel pressure while disconnecting pressure regulator vacuum hose from intake manifold.
< Ref. to INSPECTION , Fuel Pressure. >
WARNING: Release fuel pressure before removing the fuel pressure gauge.
 Is the measured value 333 - 363 kPa (3.4 - 3.7 kgf/cm2 , 48 - 53 psi)? Go to step 7.  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 supply line
7 CHECK FUEL PRESSURE. 
After connecting the pressure regulator vacuum hose, measure fuel pressure. < Ref. to INSPECTION , Fuel Pressure. >
WARNING: Release fuel pressure before removing the fuel pressure gauge.
NOTE: If the measured value at this step is out of specification, check or replace pressure regulator and pressure regulator vacuum hose.
 Is the measured value 279 - 309 kPa (2.85 - 3.15 kg/cm2 , 40 - 45 psi)? Go to step 8.  Repair the following item.
Fuel pressure is too high:
  • Faulty pressure regulator
  • Clogged fuel line or bent hose Fuel pressure is too low:
  • Faulty pressure regulator
  • Improper fuel pump discharge
  • Clogged fuel supply line
8 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 procedure, 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 Instruction Manual".

 Is the temperature above 60°C (140°F)? Go to step 9.  Replace the engine coolant temperature sensor. < Ref. to ENGINE COOLANT TEMPERATURE SENSOR . >
9 CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR. 
  1. Start the engine and warm-up engine until coolant temperature is greater than 60°C (140°F).
  2. Place the shift lever in neutral position.
  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 procedure, 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 Instruction Manual".

 Is the measured value 3.1 - 4.3 g/s (0.41 - 0.57 lb/m)? Go to step 10.  Replace the mass air flow and intake air temperature sensor. < Ref. to MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR . >
10 CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR. 
  1. Start the engine and warm-up engine until coolant temperature is greater than 60°C (140°F).
  2. Place the shift lever in neutral position.
  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 procedure, 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 Instruction Manual".

 Subtract the ambient temperature from intake air temperature. Is the obtained value -10 - 50°C(14- 122°F)? Go to step 11.  Check the mass air flow and intake air temperature sensor. < Ref. to MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR . >
11 CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from ECM and front oxygen (A/F) sensor connector.
  3. Measure the resistance of harness between ECM and front oxygen (A/F) sensor connector.

    Connector & terminal 

    (B135) No. 10 - Chassis ground: 

    (B135) No. 11 - Chassis ground: 

 Is the resistance more than 1 MO? Go to step 12.  Repair the ground short circuit of harness between ECM and front oxygen (A/F) sensor connector.
12 CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
  1. Turn the ignition switch to ON.
  2. Disconnect the connector from front oxygen (A/F) sensor.
  3. Measure the voltage of harness between ECM connector and chassis ground.

    Connector & terminal 

    (B135) No. 10 (+) - Chassis ground (-): 

    (B135) No. 11(+) - Chassis ground (-): 

 Is the voltage more than 8 V? Go to step 13.  Repair the battery short circuit of harness between ECM and front oxygen (A/F) sensor connector.
13 CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from ECM and front oxygen (A/F) sensor connector.
  3. Measure the resistance of harness between ECM and front oxygen (A/F) sensor connector.

    Connector & terminal 

    (B135) No. 10 - (E24) No. 4: 

    (B135) No. 11- (E24) No. 3: 

 Is the resistance less than 1 Ω? Go to step 14.  Repair the open circuit of harness between ECM and front oxygen (A/F) sensor connector.
14 CHECK REAR OXYGEN SENSOR DATA. 
  1. Warm-up the engine until engine coolant temperature is above 70°C (158°F), and keep the engine speed at 5,000 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 procedure, 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 Instruction Manual".

 Is the voltage more than 490 mV? Go to step 17.  Go to step 15  .
15 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. 15 - (E25) No. 3: 

    (B135) No. 30 - (E25) No. 4: 

 Is the resistance more than 3 Repair the open circuit of harness between ECM and rear oxygen sensor connector. Go to step 16  .
16 CHECK HARNESS BETWEEN REAR OXYGEN SENSOR AND ECM CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from rear oxygen sensor.
  3. Turn the ignition switch to ON.
  4. Measure the resistance between the rear oxygen sensor harness 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 rear oxygen sensor and ECM connector
  • Poor contact in rear oxygen sensor connector
  • Poor contact in ECM connector
17 CHECK REAR OXYGEN SENSOR DATA. 
  1. Warm-up the engine until engine coolant temperature is above 70°C (158°F), and drop the engine speed suddenly from 5,000 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 procedure, 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 Instruction Manual".

 Is the voltage less than 250 mV? Contact with the SOA Service Center. 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. 15 - (E25) No. 3: 

    (B135) No. 30 - (E25) No. 4: 

 Is the resistance more than 3 Ω? Repair the open circuit of harness between ECM and rear oxygen sensor connector. Go to step 19  .
19 CHECK HARNESS BETWEEN REAR OXYGEN SENSOR AND ECM CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from rear oxygen sensor.
  3. Turn the ignition switch to ON.
  4. Measure the resistance between the rear oxygen sensor harness 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 rear oxygen sensor and ECM connector
  • Poor contact in rear oxygen sensor connector
  • Poor contact in ECM connector
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