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Home >> Subaru >> 2005 >> Outback R VDC Limited >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 22 (Engine Controls - Engine (Diagnostics) (H4DOTC)) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P0172 System Too Rich (Bank 1)

DTC P0172 System Too Rich (Bank 1)

WARNING: This page is about a different variant/trim than selected.

DTC DETECTING CONDITION: 

TROUBLE SYMPTOM: 

CAUTION: After repair or replacement of faulty parts, conduct Clear Memory Mode < Ref. to , OPERATION , Clear Memory Mode.> and Inspection Mode < Ref. to , PROCEDURE , Inspection Mode.>.
DIAGNOSTIC PROCEDURE (DTC P0172)

Step Check Yes No
1 
CHECK EXHAUST SYSTEM. 		 Are there holes or loose bolts on exhaust system? Repair exhaust system. Go to step 2. 
2 
CHECK AIR INTAKE SYSTEM. 		 Are there holes, loose bolts or disconnection of hoses on air intake system? Repair air intake system. Go to step 3. 
3 
CHECK FUEL PRESSURE. 
WARNING:
  • Place "NO FIRE" signs near the working area.
  • Be careful not to spill fuel.
  1. Release the fuel pressure.
    1. Disconnect the connector from fuel pump relay.
    2. Start the engine and run it until it stalls.
    3. After the engine stalls, crank it for 5 more seconds.
    4. Turn the ignition switch to OFF.
  2. Connect the connector to fuel pump relay.
  3. Disconnect the fuel delivery hose from fuel filter, and connect the fuel pressure gauge.
  4. Install the fuel filler cap.
  5. Start the engine and idle while gear position is neutral.
  6. Measure the fuel pressure while disconnecting pressure regulator vacuum hose from intake manifold.
WARNING: Release fuel pressure before removing the fuel pressure gauge.
NOTE: If fuel pressure does not increase, squeeze the fuel return hose 2 to 3 times, then measure fuel pressure again.
 Is fuel pressure 284 - 314 kPa (2.9 - 3.2 kg/cm2 , 41 - 46 psi)? Go to step 4. Repair the following items.
Fuel pressure is too high:
  • Clogged fuel return line or bent hose

    Fuel pressure is too low:

  • Improper fuel pump discharge
  • Clogged fuel supply line
4 
CHECK FUEL PRESSURE. 
After connecting the pressure regulator vacuum hose, measure fuel pressure.
WARNING: Release fuel pressure before removing the fuel pressure gauge.
NOTE:
  • If fuel pressure does not increase, squeeze fuel return hose 2 to 3 times, then measure fuel pressure again.
  • If out of specification as measured at this step, check or replace pressure regulator and pressure regulator vacuum hose.
 Is measured value 206 - 235 kPa(2.1 - 2.4 kg/cm2 , 30 - 34 psi)? Go to step 5. Repair the following items.
Fuel pressure is too high:
  • Faulty pressure regulator
  • Clogged fuel return line or bent hose

Fuel pressure is too low:
  • Faulty pressure regulator
  • Improper fuel pump discharge
  • Clogged fuel supply line
5 
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 OBD-II general scan tool.
NOTE:
  • Subaru Select

    Monitor For detailed operation procedure, refer to the "READ CURRENT DATA SHOWN ON DISPLAY FOR ENGINE". < Ref. to , SUBARU SELECT MONITOR . >

  • OBD-II general scan tool

    For detailed operation procedure, refer to the OBD-II general scan tool instruction manual .

 Is engine coolant temperature more than 60°C (140°F)? Go to step 6. Replace the engine coolant temperature sensor. < Ref. to ENGINE COOLANT TEMPERATURE SENSOR . >
6 
CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR. 
  1. Start and warm-up the engine until engine 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 accessory switches to OFF.
  5. Read the data of mass air flow and intake air temperature sensor signal using Subaru Select Monitor or OBD-II general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedure, refer to the "READ CURRENT DATA SHOWN ON DISPLAY FOR ENGINE". < Ref. to , SUBARU SELECT MONITOR . >

  • OBD-II general scan tool

    For detailed operation procedure, refer to the OBD-II general scan tool instruction manual .

 Is the measured value within the following? Ignition ON: 73.3 - 106.6 kPa (550 - 800 mmHg, 21.65 - 31.50 inHg) Idling: 24.0 - 41.3 kPa (180 - 310 mmHg, 7.09 - 12.20 inHg) Go to step 7. Replace the mass air flow and intake air temperature sensor. < Ref. to MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR . >
7 
CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR. 
  1. Start and warm-up the engine until engine 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 accessory switches to OFF.
  5. Open the 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 OBD-II general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedure, refer to the "READ CURRENT DATA SHOWN ON DISPLAY FOR ENGINE". < Ref. to , SUBARU SELECT MONITOR . >

  • OBD-II general scan tool

    For detailed operation procedure, refer to the OBD-II general scan tool instruction manual .

 Subtract the ambient temperature from intake air temperature, and is the value from -10°C (14°F) to 50°C (122°F)? Replace the ECM. < Ref. to ENGINE CONTROL MODULE (ECM) . > Check mass air flow and intake air temperature sensor. < Ref. to MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR . >
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