P0170
DTC P0170FUEL TRIM MALFUNCTION (FUEL)
DTC Detecting Condition
Two consecutive trips with fault.
Trouble Symptom
- Erroneous idling.
- Engine stalls.
- Poor driving performance.
1. Check Exhaust System.
[CHECK]: Are there holes or loose bolts on Exhaust System?
[YES]: Repair Exhaust System.
[NO]: Go to step 2.
2. 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 3.
3. Check fuel pressure.
a. Release fuel pressure.
1. Remove Fuel Pump access hole lid located on the right rear of trunk compartment floor (Sedan) or luggage compartment floor (Wagon).
2. Disconnect connector from Fuel Tank.
3. Start the Engine and run it until it stalls.
4. After stopping the Engine, crank the Engine for 5 to 7 seconds to reduce fuel pressure.
5. Turn Ignition switch to "OFF".
b. Connect connector to Fuel Tank.
c. Disconnect Fuel Delivery Hose from Fuel Filter and connect fuel pressure gauge.
d. Start the Engine and idle while gear position is in neutral.
e. Measure fuel pressure while disconnecting pressure regulator vacuum hose from Intake Manifold.
[CHECK]: Fuel pressure:
226 - 275 kPa (2.3 - 2.8 kg/cm2, 33 - 40 psi).
[YES]: Go to next step.
[NO]: Repair the following items.
Fuel Pressure Too High:
- Clogged Fuel Return Line or bent hose.
Fuel Pressure Too Low:
- Improper Fuel Pump discharge.
- Clogged Fuel Supply Line.
e. After connecting Pressure Regulator Vacuum Hose measure fuel pressure.
[CHECK]: Fuel pressure:
157 - 206 kPa (1.6 - 2.1 kg/cm2, 23 - 30 psi).
[YES]: Go to step 4.
[NO]: Repair the following items.
Fuel Pressure Too High:
- Faulty Pressure Regulator.
- Clogged Fuel Return Line or bent hose.
Fuel Pressure Too Low:
- Faulty Pressure Regulator.
- Improper Fuel Pump discharge.
- Clogged Fuel Supply Line.
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 step 6), check or replace pressure regulator and pressure regulator vacuum hose.
4. Check engine coolant temperature sensor.(Refer to DTC P0115).
a. Turn Ignition switch to "OFF".
b. Connect the Subaru Select Monitor or the OBD-II General Scan Tool to Data Link Connector.
c. Start the Engine and warm-up completely.
d. Read data on Subaru Select Monitor or the OBD-II General Scan Tool.
Subaru Select Monitor
- Designate mode using function key.
- Function mode: FO5 or FO6
[CHECK]: Is temperature indicated on Subaru Select Monitor (FO5) greater than 14O°F?
Is temperature indicated on Subaru Select Monitor (FO6) greater than 6O°C?
[YES]: Go to step 5.
[NO]: Replace engine coolant temperature sensor.
OBD-II General Scan Tool
- For detailed operation procedures refer to the OBD-II General Scan Tool Instruction Manual.
5. Check mass air flow sensor.
a. Turn Ignition switch to "OFF".
b. Connect the Subaru Select Monitor or the OBD-II General Scan Tool to Data Link Connector.
c. Start the Engine and warm~up engine until coolant temperature is greater than 60°C (14O°F).
d. Read data on Subaru Select Monitor or OBD-II General Scan Tool.
Subaru Select Monitor
- Designate mode using function key.
- Function mode: F47.
[CHECK]: Is the voltage within the specifications shown?
[NO]: Replace mass air flow sensor.
[YES]: Contact with SOA service.
Note: Inspection by DTM is required.
Probable Cause: Deterioration of plural parts.
OBD-II General Scan Tool
- For detailed operation procedures, refer to the OBD-II General Scan Tool Instruction Manual.