DTC P219A: Bank 1 Air-Fuel Ratio Imbalance: Notes

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

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Trouble symptom:

Engine stalls.
Improper idling
CAUTION:
- After servicing or replacing faulty parts, perform Clear Memory Mode Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>CLEAR MEMORY MODE>OPERATION , and inspection mode Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>INSPECTION MODE>PROCEDURE ..
- Use the check board when measuring the ECM terminal voltage and resistance.

Wiring diagram:

Engine Electrical System Refer to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

CHECK FRONT OXYGEN (A/F) SENSOR CONNECTOR.
Check the front oxygen (A/F) sensor connector.

Has water entered the connector?

Yes: Completely remove any water inside.

No: Go to 2.
CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR.
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Disconnect the connectors from front oxygen (A/F) sensor.
4. Measure the resistance of harness between ECM connector and front oxygen (A/F) sensor connector.
  Connector & terminal
  
  (E158) No. 15 - (E24) No. 1:
  
  (E158) No. 27 - (E24) No. 4:
  
  (E158) No. 39 - (E24) No. 5:
Is the resistance less than 1 Ω?

Yes: Go to 3.

No: Repair the harness and connector.
NOTE:
In this case, repair the following item:
- Open circuit in harness between ECM connector and front oxygen (A/F) sensor connector
- Poor contact of coupling connector
CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR.
Measure the resistance between ECM connector and chassis ground.

Connector & terminal

(E158) No. 15 - Chassis ground:

(E158) No. 27 - Chassis ground:

(E158) No. 39 - Chassis ground:

Is the resistance 1 MΩ or more?

Yes: Go to 4.

No: Repair the short circuit to ground in harness between ECM connector and front oxygen (A/F) sensor connector.
CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR.
1. Connect the connector to ECM.
2. Turn the ignition switch to ON.
3. Measure the voltage between front oxygen (A/F) sensor connector and chassis ground.
  Connector & terminal
  
  (E24) No. 1 (+) - Chassis ground (-):
  
  (E24) No. 4 (+) - Chassis ground (-):
  
  (E24) No. 5 (+) - Chassis ground (-):
Is the voltage 8 V or more?

Yes: Repair the short circuit to power in the harness between ECM connector and front oxygen (A/F) sensor connector.

No: Go to 5.
CHECK EXHAUST SYSTEM.
Check the exhaust system.

Are there holes or loose bolts on exhaust system?

Yes: Repair the exhaust system.

No: Go to 6.
CHECK AIR INTAKE SYSTEM.
Check the air intake system.

Are there holes, loose bolts or disconnection of hose on air intake system?

Yes: Repair the air intake system.

No: Go to 7.
CHECK FUEL PRESSURE.
WARNING: Place "NO OPEN FLAMES" signs near the working area.
CAUTION:
- Be careful not to spill fuel.
- Before attaching/detaching a fuel pressure gauge, release the fuel pressure.
1. Connect the front oxygen (A/F) sensor connector.
2. Measure the fuel pressure. Refer to MECHANICAL (EXCEPT FOR STI)>FUEL PRESSURE>INSPECTION .
Is the measured value 340 - 400 kPa (3.5 - 4.1 kgf/cm² , 49 - 58 psi)?

Yes: Go to 8.

No: Check the fuel pump and fuel delivery line. Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>FUEL PUMP>INSPECTION . Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>FUEL DELIVERY AND EVAPORATION LINES>INSPECTION .
CHECK ENGINE COOLANT TEMPERATURE SENSOR.
1. Start the engine and warm up completely.
2. Read the value of «Coolant Temp.» using the Subaru Select Monitor or a general scan tool.
  NOTE:
  - Subaru Select Monitor
    For detailed operation procedures, refer to "Read Current Data For Engine". Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>SUBARU SELECT MONITOR .
  - General scan tool
    For detailed operation procedures, refer to the general scan tool operation manual.
Is the value of «Coolant Temp.» 75°C (167°F) or more?

Yes: Go to 9.

No: Replace the engine coolant temperature sensor. Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>ENGINE COOLANT TEMPERATURE SENSOR .
CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR.
1. Start the engine and warm up engine until coolant temperature is higher than 75°C (167°F).
2. For CVT models, set the select lever to "P" range or "N" range, and for MT models, place the gear shift lever in the neutral position.
3. Turn the A/C switch to OFF.
4. Turn all the accessory switches to OFF.
5. Read the value of «Mass Air Flow» using the Subaru Select Monitor or a general scan tool.
  NOTE:
  - Subaru Select Monitor
    For detailed operation procedures, refer to "Read Current Data For Engine". Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>SUBARU SELECT MONITOR .
  - General scan tool
    For detailed operation procedures, refer to the general scan tool operation manual.
Is the value of «Mass Air Flow» 2 - 5 g/s (0.26 - 0.66 lb/m)?

Yes: Go to 10.

No: Replace the mass air flow and intake air temperature sensor. Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .
CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR.
1. Start the engine and warm up engine until coolant temperature is higher than 75°C (167°F).
2. For CVT models, set the select lever to "P" range or "N" range, and for MT models, place the gear shift lever in the 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 value of «IAT Sensor #11» using the Subaru Select Monitor or a general scan tool.
  NOTE:
  - Subaru Select Monitor
    For detailed operation procedures, refer to "Read Current Data For Engine". Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>SUBARU SELECT MONITOR .
  - General scan tool
    For detailed operation procedures, refer to the general scan tool operation manual.
Subtract ambient temperature value from the value of «IAT Sensor #11». Is the obtained value -10 - 50°C (-18 - 90°F)?

Yes: Go to 11.

No: Check the mass air flow and intake air temperature sensor. Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .
CHECK REAR OXYGEN SENSOR DATA.
1. Warm up the engine until engine coolant temperature is higher than 75°C (167°F), and keep the engine speed at 3, 000 rpm. (2 minutes maximum)
2. Read the value of «Oxygen sensor #12» using the Subaru Select Monitor or a general scan tool.
  NOTE:
  - Subaru Select Monitor
    For detailed operation procedures, refer to "Read Current Data For Engine". Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>SUBARU SELECT MONITOR .
  - General scan tool
    For detailed operation procedures, refer to the general scan tool operation manual.
Is the value of «Oxygen sensor #12» 0.490 V or more?

Yes: Go to 12.

No: Go to 13.
CHECK REAR OXYGEN SENSOR DATA.
1. Warm up the engine until engine coolant temperature is higher than 75°C (167°F), and rapidly reduce the engine speed from 3, 000 rpm.
2. Read the value of «Oxygen sensor #12» using the Subaru Select Monitor or a general scan tool.
  NOTE:
  - Subaru Select Monitor
    For detailed operation procedures, refer to "Read Current Data For Engine". Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>SUBARU SELECT MONITOR .
  - General scan tool
    For detailed operation procedures, refer to the general scan tool operation manual.
Is the value of «Oxygen sensor #12» 0.250 V or less?

Yes: Go to 14.

No: Go to 13.
CHECK REAR OXYGEN SENSOR CONNECTOR.
Check the rear oxygen sensor connector.

Has water entered the connector?

Yes: Completely remove any water inside.

No: Go to 15.
CHECK FRONT OXYGEN (A/F) SENSOR USING REAR OXYGEN SENSOR SIGNAL.
1. Warm up the engine until engine coolant temperature is higher than 75°C (167°F), then keep the engine idling for 5 minutes or more.
2. Read the value of «Oxygen sensor #12» using the Subaru Select Monitor or a general scan tool.
  NOTE:
  - Subaru Select Monitor
    For detailed operation procedures, refer to "Read Current Data For Engine". Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>SUBARU SELECT MONITOR .
  - General scan tool
    For detailed operation procedures, refer to the general scan tool operation manual.
Is the value of «Oxygen sensor #12» kept at 0.250 V or less for 5 minutes or more?

Yes: Replace the front oxygen (A/F) sensor. Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>FRONT OXYGEN (A/F) SENSOR .

No: Go to 15.
CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR.
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Disconnect the connector from rear oxygen sensor.
4. Measure the resistance of harness between ECM connector and rear oxygen sensor connector.
  Connector & terminal
  
  (E158) No. 42 - (E25) No. 3:
  
  (E158) No. 16 - (E25) No. 4:
Is the resistance less than 1 Ω?

Yes: Go to 16.

No: Repair the harness and connector.
NOTE:
In this case, repair the following item:
- Open circuit in harness between ECM connector and rear oxygen sensor connector
- Poor contact of coupling connector
CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR.
1. Connect the connector to ECM.
2. Turn the ignition switch to ON.
3. Measure the voltage between rear oxygen sensor connector and chassis ground.
  Connector & terminal
  
  (E25) No. 4 (+) - Chassis ground (-):
Is the voltage 0.2 - 0.5 V?

Yes: Replace the rear oxygen sensor. Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>REAR OXYGEN SENSOR .

No: Go to 17.
CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR.
1. Turn the ignition switch to OFF.
2. Disconnect the connector from fuel injector on faulty cylinders.
3. Measure the resistance between fuel injector connector and engine ground on faulty cylinders.
  Connector & terminal
  
  #1 (E5) No. 1 - Engine ground:
  
  #1 (E5) No. 2 - Engine ground:
  
  #2 (E16) No. 1 - Engine ground:
  
  #2 (E16) No. 2 - Engine ground:
  
  #3 (E6) No. 1 - Engine ground:
  
  #3 (E6) No. 2 - Engine ground:
  
  #4 (E17) No. 1 - Engine ground:
  
  #4 (E17) No. 2 - Engine ground:
Is the resistance 1 MΩ or more?

Yes: Go to 18.

No: Repair the short circuit to ground in harness between ECM connector and fuel injector connector.
CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR.
Measure the resistance of harness between ECM and fuel injector connector on faulty cylinders.

Connector & terminal

#1 (E158) No. 12 - (E5) No. 1:

#1 (E158) No. 11 - (E5) No. 2:

#2 (E158) No. 24 - (E16) No. 1:

#2 (E158) No. 23 - (E16) No. 2:

#3 (E158) No. 36 - (E6) No. 1:

#3 (E158) No. 35 - (E6) No. 2:

#4 (E158) No. 48 - (E17) No. 1:

#4 (E158) No. 47 - (E17) No. 2:

Is the resistance less than 1 Ω?

Yes: Go to 19.

No: Repair the open circuit of the harness between the ECM connector and fuel injector connector.
CHECK FUEL INJECTOR.
Check the fuel injector on faulty cylinder. Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>FUEL INJECTOR>INSPECTION .

Is the check result OK?

Yes: Go to 20.

No: Replace the faulty fuel injector. Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>FUEL INJECTOR .
CHECK INSTALLATION CONDITION OF CAMSHAFT POSITION SENSOR/CRANKSHAFT POSITION SENSOR.
Check installation condition of the camshaft position sensor and crankshaft position sensor.

Is the camshaft position sensor or crankshaft position sensor loosely installed?

Yes: Tighten the camshaft position sensor or crankshaft position sensor. Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>CAMSHAFT POSITION SENSOR>INSTALLATION . Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>CRANKSHAFT POSITION SENSOR>INSTALLATION .

No: Go to 21.
CHECK CRANKSHAFT POSITION SENSOR PLATE.
Check the crankshaft position sensor plate.

Is the crankshaft position sensor plate rusted or does it have broken teeth?

Yes: Replace the crankshaft position sensor plate. Refer to MECHANICAL (EXCEPT FOR STI)>CYLINDER BLOCK .

No: Go to 22.
CHECK INSTALLATION CONDITION OF TIMING CHAIN.
Turn the crankshaft using ST, and align the alignment mark on crank sprocket with alignment mark on cylinder block.

ST 18252AA000 CRANKSHAFT SOCKET

Is the timing chain dislocated from its proper position?

Yes: Correct the installation condition of timing chain. Refer to MECHANICAL (EXCEPT FOR STI)>TIMING CHAIN ASSEMBLY .

No: Go to 23.
CHECK FUEL LEVEL.
Check display of fuel gauge.

Is the fuel meter indication higher than the "Lower" level?

Yes: Go to 24.

No: Refill the fuel so that the fuel meter indication is higher than the "Lower" level, and proceed to the next step. Go to 24.
CHECK STATUS OF MALFUNCTION INDICATOR LIGHT.
1. Clear the memory using the Subaru Select Monitor or general scan tool. Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>CLEAR MEMORY MODE .
2. Start the engine, and drive the vehicle for 10 minutes or more at 60 km/h (37.3 MPH) or more.
Does the malfunction indicator light illuminate or blink?

Yes: Go to 25.

No: Repair the poor contact of connector.
NOTE:
In this case, repair the following item:
- Poor contact of ignition coil connector
- Poor contact of fuel injector connector on faulty cylinders
- Poor contact of ECM connector
- Poor contact of coupling connector
CHECK AIR INTAKE SYSTEM.
Check installation condition of the air intake system.

Is there any fault in air intake system?

Yes: Repair the air intake system.
NOTE:
Check the following items.
- Are there air leaks or air suction caused by loose or dislocated nuts and bolts?
- Are there cracks or any disconnection of hoses?
No: Go to 26.
CHECK MISFIRE SYMPTOM.
1. Turn the ignition switch to ON.
2. Check for DTC. Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>READ DIAGNOSTIC TROUBLE CODE (DTC) .
Does the Subaru Select Monitor or general scan tool indicate only one DTC?

Yes: Go to 29.

No: Go to 27.
CHECK DTC.
Read the engine DTC using the Subaru Select Monitor or general scan tool. Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>READ DIAGNOSTIC TROUBLE CODE (DTC) .

Are DTC P0301 and P0303 displayed? (Current malfunction)

Yes: Go to 30.

No: Go to 28.
CHECK DTC.
Read the engine DTC using the Subaru Select Monitor or general scan tool. Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>READ DIAGNOSTIC TROUBLE CODE (DTC) .

Are DTC P0302 and P0304 displayed? (Current malfunction)

Yes: Go to 31.

No: Go to 32.
ONLY ONE CYLINDER.
Check the following items for one cylinder only.
- Spark plug
- Ignition coil
- Fuel injector
- Compression
Is there any fault in the cylinder?

Yes: Repair or replace faulty parts.
NOTE:
Check the following items.
- Spark plug
- Ignition coil
- Fuel injector
- Compression
No: Go to DTC P0171. Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171 SYSTEM TOO LEAN BANK 1 .
GROUP OF #1 AND #3 CYLINDERS.
Check the following items for groups of #1 and #3 cylinders.
- Spark plug
- Ignition coil
- Fuel injector
- Compression
- Skipping timing chain teeth
Are there any faults in #1 and #3 cylinders?

Yes: Repair or replace faulty parts.
NOTE:
Check the following items.
- Spark plug
- Ignition coil
- Fuel injector
- Compression
- Skipping timing chain teeth
No: Go to DTC P0171. Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171 SYSTEM TOO LEAN BANK 1 .
GROUP OF #2 AND #4 CYLINDERS.
Check the following items for groups of #2 and #4 cylinders.
- Spark plug
- Ignition coil
- Fuel injector
- Compression
- Skipping timing chain teeth
Are there any faults in #2 and #4 cylinders?

Yes: Repair or replace faulty parts.
NOTE:
Check the following items.
- Spark plug
- Ignition coil
- Fuel injector
- Compression
- Skipping timing chain teeth
No: Go to DTC P0171. Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171 SYSTEM TOO LEAN BANK 1 .
CYLINDER AT RANDOM.
1. Start the engine.
2. Check the idling.
Is the engine idle rough?

Yes: Go to DTC P0171. Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171 SYSTEM TOO LEAN BANK 1 .

No: Repair or replace faulty parts.
NOTE:
Check the following items.
- Spark plug
- Ignition coil
- Fuel injector
- Compression