DTC P219C: Cylinder 1 Air-Fuel Ratio Imbalance: Notes

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

1. -

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Trouble symptom:

Engine stall
Improper idling

Wiring diagram:

Engine Electrical System Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV))>ENGINE ELECTRICAL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO (HEV))>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .

NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DO (HEV))>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

Courtesy of SUBARU OF AMERICA, INC.

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 AND COUPLING CONNECTOR .
Check the front oxygen (A/F) sensor connector and coupling 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 (OPEN) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Disconnect the connector from the 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. 3 - (B379) No. 3:
  
  (E158) No. 4 - (B379) No. 4:
Is the resistance less than 1 Ω?

Yes : Go to 3.

No : Check the harnesses and connectors, and repair or replace them if necessary.
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 (SHORT TO GROUND) .
Measure the resistance between the ECM connector and engine ground.

Connector & terminal

(E158) No. 3 - Engine ground:

(E158) No. 4 - Engine 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 OUTPUT SIGNAL OF ECM .
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 engine ground.
  Connector & terminal
  
  (B379) No. 3 (+) - Engine ground (-):
Is the voltage 4.5 V or more?

Yes : Go to 6.

No : Go to 5.
CHECK OUTPUT SIGNAL OF ECM .
Measure the voltage between front oxygen (A/F) sensor connector and engine ground.

Connector & terminal

(B379) No. 4 (+) - Engine ground (-):

Is the voltage 4.95 V or more?

Yes : Go to 6.

No : Go to 7.
CHECK OUTPUT SIGNAL OF ECM .
Measure the voltage between front oxygen (A/F) sensor connector and engine ground.

Connector & terminal

(B379) No. 3 (+) - Engine ground (-):

(B379) No. 4 (+) - Engine 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. After repair, replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>ENGINE CONTROL MODULE (ECM) .

No : Repair the poor contact of ECM connector.
CHECK EXHAUST SYSTEM .
Check exhaust system parts.

Are there holes or loose bolts on exhaust system?

Yes : Repair the exhaust system.

No : Go to 8.
CHECK AIR INTAKE SYSTEM .
Check the installing condition of 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 9.
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. Ref. to MECHANICAL (H4DO (EXCEPT FOR HEV))>FUEL PRESSURE>INSPECTION .
Is the measured value 350 - 450 kPa (3.5 - 4.6 kg/cm² , 50 - 66 psi)?

Yes : Go to 10.

No : Check the fuel pump and fuel delivery line. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>FUEL PUMP>INSPECTION . Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>FUEL DELIVERY AND EVAPORATION LINES>INSPECTION .
CHECK ENGINE COOLANT TEMPERATURE SENSOR .
1. Turn the ignition switch to ON.
2. Navigate to Inspection Mode for measuring Exhaust Gas. Ref. to P-HEV HYBRID POWERTRAIN CONTROL (DIAGNOSTICS)>WORK SUPPORT>OPERATION>SERVICE MODE .
  NOTE: If it is necessary to run the engine for 10 minutes or more, fasten the driver's seat belt.
3. Start the engine and warm up completely.
4. Using the Subaru Select Monitor, read the value of [Engine Coolant Temperature] of the data monitor.
  NOTE: For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (DIAG)>DATA MONITOR .
Is the value of [Engine Coolant Temperature] 75[°C] (167°F) or more?

Yes : Go to 11.

No : Replace the engine coolant temperature sensor (outlet). Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>ENGINE COOLANT TEMPERATURE SENSOR .
CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .
1. Turn the ignition switch to ON.
2. Navigate to Inspection Mode for measuring Exhaust Gas. Ref. to P-HEV HYBRID POWERTRAIN CONTROL (DIAGNOSTICS)>WORK SUPPORT>OPERATION>SERVICE MODE .
  NOTE: If it is necessary to run the engine for 10 minutes or more, fasten the driver's seat belt.
3. Start the engine.
4. Warm up the engine until coolant temperature is higher than 75°C (167°F).
5. Place the select lever in "P" range or "N" range.
6. Turn the A/C switch to OFF.
7. Turn all the accessory switches to OFF.
8. Using the Subaru Select Monitor, read the value of [Mass Air Flow] of the data monitor.
  NOTE: For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (DIAG)>DATA MONITOR .
Is the value of [Mass Air Flow] 2 - 5 [g/s] (0.26 - 0.66 lb/min)?

Yes : Go to 12.

No : Replace the mass air flow and intake air temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .
CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .
1. Turn the ignition switch to ON.
2. Navigate to Inspection Mode for measuring Exhaust Gas. Ref. to P-HEV HYBRID POWERTRAIN CONTROL (DIAGNOSTICS)>WORK SUPPORT>OPERATION>SERVICE MODE .
  NOTE: If it is necessary to run the engine for 10 minutes or more, fasten the driver's seat belt.
3. Start the engine.
4. Warm up the engine until coolant temperature is higher than 75°C (167°F).
5. Place the select lever in "P" range or "N" range.
6. Turn the A/C switch to OFF.
7. Turn all the accessory switches to OFF.
8. Open the front hood.
9. Measure the ambient temperature.
10. Using the Subaru Select Monitor, read the value of [Intake Air Temp.] of the data monitor.
  NOTE: For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (DIAG)>DATA MONITOR .
Subtract ambient temperature from [Intake Air Temp.]. Is the obtained value -10 - 50[°C] (-18 - 90°F)?

Yes : Go to 13.

No : Check the mass air flow and intake air temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR>INSPECTION .
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 14.
CHECK FRONT OXYGEN (A/F) SENSOR USING REAR OXYGEN SENSOR SIGNAL .
1. Turn the ignition switch to ON.
2. Navigate to Inspection Mode for measuring Exhaust Gas. Ref. to P-HEV HYBRID POWERTRAIN CONTROL (DIAGNOSTICS)>WORK SUPPORT>OPERATION>SERVICE MODE .
  NOTE: If it is necessary to run the engine for 10 minutes or more, fasten the driver's seat belt.
3. Start the engine.
4. Warm up the engine until the engine coolant temperature exceeds 75°C (167°F) and leave it at idling for 5 minutes or more.
5. Using the Subaru Select Monitor, read the value of [Oxygen sensor #12] of the data monitor.
  NOTE: For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (DIAG)>DATA MONITOR .
Is the value of [Oxygen sensor #12] kept at 0.25 [V] or less for 5 minutes or more?

Yes : Replace the front oxygen (A/F) sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>FRONT OXYGEN (A/F) SENSOR .

No : Go to 15.
CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR (OPEN) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Disconnect the connector from the rear oxygen sensor.
4. Measure the resistance of harness between ECM connector and rear oxygen sensor connector.
  Connector & terminal
  
  (B134) No. 33 - (B19) No. 3:
  
  (B134) No. 44 - (B19) No. 4:
Is the resistance less than 1 Ω?

Yes : Go to 16.

No : Repair the open circuit of harness between ECM connector and rear oxygen sensor 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 engine ground.
  Connector & terminal
  
  (B19) No. 3 (+) - Engine ground (-):
Is the voltage 0.2 - 0.5 V?

Yes : Replace the rear oxygen sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>REAR OXYGEN SENSOR .

No : Go to 17.
CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR (SHORT TO POWER SUPPLY) .
Measure the voltage between rear oxygen sensor connector and engine ground.

Connector & terminal

(B19) No. 3 (+) - Engine ground (-):

Is the voltage 0.15 V or more?

Yes : Repair the short circuit to power supply in harness between ECM connector and rear oxygen sensor connector.

No : Go to 18.
CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR (SHORT TO GROUND) .
1. Turn the ignition switch to OFF.
2. Measure the resistance between the ECM connector and engine ground.
  Connector & terminal
  
  (B134) No. 33 (+) - Engine ground (-):
Is the resistance 1 MΩ or more?

Yes : Go to 19.

No : Repair the short circuit to ground in harness between ECM connector and rear oxygen sensor connector.
CHECK EXHAUST SYSTEM .
Check exhaust system parts.
NOTE:
Check the following items.
- Looseness and improper fitting of exhaust system parts
- Damage (crack, hole etc.) of parts
- Damage (crack, hole etc.) between front oxygen (A/F) sensor and rear oxygen sensor
Is there any fault in exhaust system?

Yes : Repair or replace faulty parts.

No : Go to 20.
CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR (SHORT TO GROUND) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Disconnect the connector from fuel injector on faulty cylinders.
4. 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 21.

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

Connector & terminal

#1 (E158) No. 96 - (E5) No. 1:

#1 (E158) No. 87 - (E5) No. 2:

#2 (E158) No. 95 - (E16) No. 1:

#2 (E158) No. 86 - (E16) No. 2:

#3 (E158) No. 93 - (E6) No. 1:

#3 (E158) No. 84 - (E6) No. 2:

#4 (E158) No. 94 - (E17) No. 1:

#4 (E158) No. 85 - (E17) No. 2:

Is the resistance less than 1 Ω?

Yes : Go to 22.

No : Repair the open circuit in harness between ECM and fuel injector connector.
CHECK FUEL INJECTOR .
Check the fuel injector on faulty cylinder. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>FUEL INJECTOR>INSPECTION .

Is the check result OK?

Yes : Go to 23.

No : Replace the faulty fuel injector. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>FUEL INJECTOR .
CHECK INSTALLATION CONDITION OF CAMSHAFT POSITION SENSOR AND CRANKSHAFT POSITION SENSOR .
Check the 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. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>CAMSHAFT POSITION SENSOR>INSTALLATION . Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>CRANKSHAFT POSITION SENSOR>INSTALLATION .

No : Go to 24.
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. Ref. to MECHANICAL (H4DO (EXCEPT FOR HEV))>CYLINDER BLOCK .

No : Go to 25.
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. Ref. to MECHANICAL (H4DO (EXCEPT FOR HEV))>TIMING CHAIN ASSEMBLY .

No : Go to 26.
CHECK STATUS OF MALFUNCTION INDICATOR LIGHT .
1. Using the Subaru Select Monitor or a general scan tool, perform the clear memory of [Engine]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
2. Turn to READY ON.
3. Press the hybrid mode switch to switch to the hybrid battery save mode.
  NOTE:
  Even if switched to the hybrid battery save mode under the following conditions, the engine may not start.
  - Power from HV battery is low and reduction in SOC is slight.
  - SOC is recovering due to regeneration, etc.
4. Drive the vehicle at 60 km/h (37.3 MPH) or more for 10 minutes or more.
  WARNING: Use special care with the traffic condition on the public road and prioritize safety driving.
  
  NOTE: Refill the fuel before driving so that the fuel level meter indicates above "Lower" level.
Does the malfunction indicator light illuminate or blink?

Yes : 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
No : Go to 27.
CHECK AIR INTAKE SYSTEM .
Check the installing condition of the air intake system.

Is the check result OK?

Yes : Go to 28.

No : Repair the following item.
- Are there air leaks or air suction caused by loose or dislocated nuts and bolts?
- Are there cracks or any disconnection of hoses?
CHECK MISFIRE SYMPTOM .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAG)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is there only one DTC displayed? (Current malfunction)

Yes : Go to 31.

No : Go to 29.
CHECK DTC .
Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAG)>DIAGNOSTIC TROUBLE CODE (DTC) .

Are DTC P0301 and P0303 displayed? (Current malfunction)

Yes : Go to 32.

No : Go to 30.
CHECK DTC .
Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAG)>DIAGNOSTIC TROUBLE CODE (DTC) .

Are DTC P0302 and P0304 displayed? (Current malfunction)

Yes : Go to 33.

No : Go to 34.
CHECK CYLINDER .
Check the following items for cylinder.
- Spark plug
- Ignition coil
- Fuel injector
- Compression pressure
- Skipping timing chain teeth
Is there any fault in the cylinder?

Yes : Repair or replace faulty parts.

No : Go to DTC P0171. Ref. to ENGINE (DIAGNOSTICS) (H4DO (HEV))>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171 SYSTEM TOO LEAN BANK 1 .
CHECK #1 AND #3 CYLINDER .
Check the following items for the bank RH (cylinder #1, #3).
- Spark plug
- Ignition coil
- Fuel injector
- Compression pressure
- Skipping timing chain teeth
Are there any faults in #1 and #3 cylinders?

Yes : Repair or replace faulty parts.

No : Go to DTC P0171. Ref. to ENGINE (DIAGNOSTICS) (H4DO (HEV))>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171 SYSTEM TOO LEAN BANK 1 .
CHECK #2 AND #4 CYLINDER .
Check the following items for the bank LH (cylinder #2, #4).
- Spark plug
- Ignition coil
- Fuel injector
- Compression pressure
- Skipping timing chain teeth
Are there any faults in #2 and #4 cylinders?

Yes : Repair or replace faulty parts.

No : Go to DTC P0171. Ref. to ENGINE (DIAGNOSTICS) (H4DO (HEV))>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171 SYSTEM TOO LEAN BANK 1 .
CYLINDER AT RANDOM .
1. Turn the ignition switch to ON.
2. Navigate to Inspection Mode for measuring Exhaust Gas. Ref. to P-HEV HYBRID POWERTRAIN CONTROL (DIAGNOSTICS)>WORK SUPPORT>OPERATION>SERVICE MODE .
  NOTE: If it is necessary to run the engine for 10 minutes or more, fasten the driver's seat belt.
3. Start the engine.
4. Check the idling condition.
Is the engine idle rough?

Yes : Go to DTC P0171. Ref. to ENGINE (DIAGNOSTICS) (H4DO (HEV))>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171 SYSTEM TOO LEAN BANK 1 .

No : Even if DTC is detected, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

NOTE: In this case, temporary open or short circuit of harness or temporary poor contact of connector may be the cause.