P0172
U: DTC P0172 - FUEL TRIM MALFUNCTION (A/F TOO RICH)DTC DETECTING CONDITION:
- Two consecutive driving cycles with fault
TROUBLE SYMPTOM:
- Erroneous idling
- Engine stalls.
- Poor driving performance
CAUTION: After repair or replacement of faulty parts, conduct CLEAR MEMORY MODE and INSPECTION MODE. Refer to How To Clear Diagnostic Trouble Codes.
10U1: CHECK EXHAUST SYSTEM
CHECK: Are there holes or loose bolts on exhaust system?
YES: Repair exhaust system.
NO: Go to step 10U2.
10U2: CHECK AIR INTAKE SYSTEM.
CHECK: Are there holes, loose bolts or disconnection of hose on air intake system?
YES: Repair air intake system.
NO: Go to step 10U3.
10U3: CHECK FUEL PRESSURE.
WARNING:
- PLACE "NO SMOKING" SIGNS NEAR THE WORKING AREA.
- BE CAREFUL NOT TO SPILL FUEL ON THE FLOOR.
1. Release fuel pressure.
1. Disconnect connector from fuel pump relay.
2. Start the engine and run it until it stalls.
3. After the engine stalls crank it for five more seconds.
4. Turn ignition switch to OFF.
2. Connect connector to fuel pump relay.
3. Disconnect fuel delivery hose from fuel filter, and connect fuel pressure gauge.
4. Install fuel filler cap.
5. Start the engine and idle while gear position is neutral.
6. Measure fuel pressure while disconnecting pressure regulator vacuum hose from intake manifold.
WARNING: BEFORE REMOVING FUEL PRESSURE GAUGE, RELEASE FUEL PRESSURE.
NOTE: If fuel pressure does not increase, squeeze fuel return hose 2 to 3 times, then measure fuel pressure again.
CHECK: Is fuel pressure between 284 and 314 kPa (2.9 - 3.2 kg/Sq.cm, 41 - 46 psi)?
YES: Go to step 10U4.
NO: Repair the following items.
10U4: CHECK FUEL PRESSURE.
After connecting pressure regulator vacuum hose, measure fuel pressure.
WARNING: BEFORE REMOVING FUEL PRESSURE GAUGE, RELEASE FUEL PRESSURE.
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.
CHECK: Is fuel pressure between 206 and 235 kPa (2.1 - 2.4 kg/Sq.cm, 30 - 34 psi)?
YES: Go to step 10U5.
NO: Repair the following items.
10U5: CHECK ENGINE COOLANT TEMPERATURE SENSOR.
1. Start the engine and warm-up completely.
2. Read 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". Refer to Normal Scan Data values.
- OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II General Scan Tool Instruction Manual.
CHECK: Is temperature greater than 60 °C (140 °F)?
YES: Go to step 10U6.
NO: Replace engine coolant temperature sensor.
10U6: CHECK INTAKE MANIFOLD PRESSURE 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 A/C switch to OFF.
4. Turn all accessory switches to OFF.
5. Read data of intake manifold pressure 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". Refer to Normal Scan Data Values.
- OBD-II general scan tool
For detailed operation procedure, refer to the OBD-II General Scan Tool Instruction Manual.
Specification:
- Intake manifold absolute pressure
CHECK: Is the value within the specifications?
YES: Go to step 10U7.
NO: Replace intake manifold pressure sensor.
10U7: CHECK 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 A/C switch to OFF.
4. Turn all accessory switches to OFF.
5. Open front hood.
6. Measure ambient temperature.
7. Read data of intake manifold pressure sensor signal using Subaru Select Monitor or OBD-II general scan tool.
NOTE:
- Subaru Select Monitor
For detailed operation procedure, meter to the "READ CURRENT DATA SHOWN ON DISPLAY FOR ENGINE". Refer to Normal Scan Data Values.
- OBD-II general scan tool
For detailed operation procedure, refer to the OBD-II General Scan Tool Instruction Manual.
CHECK: Is value obtained when ambient temperature is subtracted from intake air temperature greater than -10 °C (14 °F ) and less than 50 °C (122 °F)?
YES: Contact with Subaru of America (SOA) service.
NOTE: Inspection by Subaru of America's DTM is required, because probable cause is deterioration of multiple parts.
NO: Check intake air temperature sensor.