P0170
DTC P0170 - FUEL TRIM MALFUNCTIONDTC 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.
11S1: CHECK EXHAUST SYSTEM.
CHECK: Are there holes or loose bolts on exhaust system?
YES: Repair exhaust system.
NO: Go to step 11S2.
11S2: 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 11S3.
111S3: 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 11S4.
NO: Repair the following items.
11S4: 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 11S5.
NO: Repair the following items.
11S5: 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 How To Clear Diagnostic Trouble Codes.
- OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II General Scan Tool Instruction Manual.
CHECK: Is temperature between 70 °C (158 °F) and 100 °C (212 °F)?
YES: Go to step 11S6.
NO: Replace engine coolant temperature sensor.
11S6: CHECK INTAKE MANIFOLD PRESSURE SENSOR SIGNAL.
1. Start the engine and warm-up engine until coolant temperature is greater than 60 °C (140 °F).
2. Place the selector lever in "N" or "P" 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 How To Clear Diagnostic Trouble Codes.
- OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II General Scan Tool Instruction Manual.
SPECIFICATION
CHECK: Is the voltage within the specifications?
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: Replace intake air temperature and pressure sensor.