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Home >> Subaru >> 2017 >> Legacy 3.6R Limited >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 14 (Engine Control System (Diagnostics) (P2101 To U1712) (H4DO)) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P219C: Cylinder 1 Air-Fuel Ratio Imbalance >> Notes

DTC P219C: Cylinder 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: 

CAUTION:
  • After servicing or replacing faulty parts, perform Clear Memory Mode Ref. to OPERATION , Clear Memory Mode, and Inspection Mode Ref. to PROCEDURE , Inspection Mode.
  • Use the check board when measuring the ECM terminal voltage and resistance.

Wiring diagram: 

Engine Electrical System Ref. to WIRING DIAGRAM , Engine Electrical System.

Fig 1: Cylinder 1 Air-Fuel Ratio Imbalance - Wiring Diagram (1 Of 3)
G11583295Courtesy of SUBARU OF AMERICA, INC.
Fig 2: Cylinder 1 Air-Fuel Ratio Imbalance - Wiring Diagram (2 Of 3)
G11583301Courtesy of SUBARU OF AMERICA, INC.
Fig 3: Cylinder 1 Air-Fuel Ratio Imbalance - Wiring Diagram (3 Of 3)
G11583292Courtesy of SUBARU OF AMERICA, INC.
Step Check Yes No
1 CHECK FRONT OXYGEN (A/F) SENSOR CONNECTOR AND COUPLING CONNECTOR.  Has water entered the connector? Completely remove any water inside. Go to step 2  .
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. 46 - (E24) No. 3: 
(E158) No. 33 - (E24) No. 4: 		 Is the resistance less than 1 Ω? Go to step 3  . Repair the open circuit of harness between ECM connector and front oxygen (A/F) sensor connector.
3 CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR.
Measure the resistance between ECM connector and chassis ground.
Connector & terminal 
(E158) No. 46 - Chassis ground: 
(E158) No. 33 - Chassis ground: 		 Is the resistance 1 MΩ or more? Go to step 4  . Repair the short circuit to ground in harness between ECM connector and front oxygen (A/F) sensor connector.
4 CHECK OUTPUT SIGNAL FOR 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 chassis ground.

Connector & terminal 
(E24) No. 3 (+) - Chassis ground (-): 		 Is the voltage 4.5 V or more? Go to step 6  . Go to step 5  .
5 CHECK OUTPUT SIGNAL FOR ECM. 
Measure the voltage between front oxygen (A/F) sensor connector and chassis ground.
Connector & terminal 
(E24) No. 4 (+) - Chassis ground (-): 		 Is the voltage 4.95 V or more? Go to step 6  Go to step 7 
6 CHECK OUTPUT SIGNAL FOR ECM. 
Measure the voltage between front oxygen (A/F) sensor connector and chassis ground.
Connector & terminal 
(E24) No. 3 (+) - Chassis ground (-): 
(E24) No. 4 (+) - Chassis ground (-): 		 Is the voltage 8 V or more? 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 ENGINE CONTROL MODULE (ECM) Repair the poor contact of ECM connector.
7 CHECK EXHAUST SYSTEM  Are there holes or loose bolts on exhaust system? Repair the exhaust system. Go to step 8 
8 CHECK AIR INTAKE SYSTEM  Are there holes, loose bolts or disconnection of hose on air intake system? Repair the air intake system. Go to step 9 
9 CHECK FUEL PRESSURE. 
WARNING: Place "NO OPEN FLAMES" signs near the working area.
CAUTION: Be careful not to spill fuel.
  1. Connect the front oxygen (A/F) sensor connector.
  2. Measure the fuel pressure. Ref. to INSPECTION , Fuel Pressure.
CAUTION: Before attaching/detaching a fuel pressure gauge, release the fuel pressure.
 Is the measured value 340 - 400 kPa (3.5 - 4.1 kg/cm2 , 49 - 58 psi)? Go to step 10  Check the fuel pump and fuel delivery line. Ref. to INSPECTION , Fuel Pump. Ref. to INSPECTION , Fuel Delivery and Evaporation Lines.
10 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 "Current Data Display For Engine". Ref. to 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? Go to step 11  Replace the engine coolant temperature sensor. Ref. to ENGINE COOLANT TEMPERATURE SENSOR
11 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 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 "Current Data Display For Engine". Ref. to 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» 2.0 - 5.0 g/s (0.26 - 0.66 lb/m)? Go to step 12  Replace the mass air flow and intake air temperature sensor. Ref. to MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR
12 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 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 «Intake Air Temp.» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Current Data Display For Engine". Ref. to SUBARU SELECT MONITOR

  • General scan tool

For detailed operation procedures, refer to the general scan tool operation manual.		 Subtract ambient temperature from «Intake Air Temp.».
Is the obtained value -10 - 50°C (-18 - 90°F)?		 Go to step 13  Check the mass air flow and intake air temperature sensor. Ref. to MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR
13 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:
  • Depress the clutch pedal (MT model)
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Current Data Display For Engine". Ref. to 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? Go to step 14  Go to step 15 
14 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:
  • Depress the clutch pedal (MT model)
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Current Data Display For Engine". Ref. to 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? Go to step 16  Go to step 15 
15 CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR.  Has water entered the connector? Completely remove any water inside. Go to step 17  .
16 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 "Current Data Display For Engine". Ref. to 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 for 5 minutes or more? Replace the front oxygen (A/F) sensor. Ref. to FRONT OXYGEN (A/F) Sensor.> Go to step 17 
17 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. 57 - (E25) No. 3: 
(E158) No. 56 - (E25) No. 4: 		 Is the resistance less than 1 Ω? Go to step 18  . Repair the open circuit of harness between ECM connector and rear oxygen sensor connector.
18 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. 3 (+) - Chassis ground (-): 		 Is the voltage 0.2 - 0.5 V? Replace the rear oxygen sensor. Ref. to REAR OXYGEN SENSOR Go to step 19 
19 CHECK OUTPUT SIGNAL OF ECM. 
  1. Turn the ignition switch to ON.
  2. Measure the voltage between ECM and chassis ground on faulty cylinders.

Connector & terminal 
DTC P219C; #1 (E158) No. 23 (+) - Chassis ground (-): 
DTC P219D; #2 (E158) No. 8 (+) - Chassis ground (-): 
DTC P219E; #3 (E158) No. 9 (+) - Chassis ground (-): 
DTC P219F; #4 (E158) No. 22 (+) - Chassis ground (-): 		 Is the voltage 10 V or more? Go to step 24  . Go to step 20  .
20 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 

    DTC P219C; #1 (E5) No. 1 - Engine ground: 

    DTC P219D; #2 (E16) No. 1 - Engine ground: 

    DTC P219E; #3 (E6) No. 1 - Engine ground: 

    DTC P219F; #4 (E17) No. 1 - Engine ground: 

 Is the resistance 1 MΩ or more? Go to step 21  . Repair the short circuit to ground in harness between ECM connector and fuel injector connector.
21 CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR. 
Measure the resistance of harness between ECM and fuel injector connector on faulty cylinders.
Connector & terminal 
DTC P219C; #1 (E158) No. 23 - (E5) No. 1: 
DTC P219D; #2 (E158) No. 8 - (E16) No. 1: 
DTC P219E; #3 (E158) No. 9 - (E6) No. 1: 
DTC P219F; #4 (E158) No. 22 - (E17) No. 1: 		 Is the resistance less than 1 Ω? Go to step 22  Open circuit in harness between ECM connector and fuel injector connector
22 CHECK FUEL INJECTOR. 
Measure the resistance between fuel injector terminals on faulty cylinder.
Terminals 
No. 1 - No. 2: 		 Is the resistance 5 - 20 Ω? Go to step 23  Replace the faulty fuel injector. Ref. to FUEL INJECTOR
23 CHECK POWER SUPPLY LINE. 
  1. Turn the ignition switch to ON.
  2. Measure the voltage between fuel injector connector of faulty cylinders and engine ground.

Connector & terminal 
DTC P219C; #1 (E5) No. 2 (+) - Engine ground (-): 
DTC P219D; #2 (E16) No. 2 (+) - Engine ground (-): 
DTC P219E; #3 (E6) No. 2 (+) - Engine ground (-): 
DTC P219F; #4 (E17) No. 2 (+) - Engine ground (-): 		 Is the voltage 10 V or more? Repair the poor contact of all connectors in fuel injector circuit. Repair the harness and connector.
NOTE: In this case, repair the following item:
  • Open circuit in harness between the main relay and fuel injector connector on faulty cylinders
  • Poor contact of coupling connector
  • Poor contact of main relay connector
24 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. Turn the ignition switch to ON.
  4. Measure the voltage between ECM and chassis ground on faulty cylinders.

Connector & terminal 
DTC P219C; #1 (E158) No. 23 (+) - Chassis ground (-): 
DTC P219D; #2 (E158) No. 8 (+) - Chassis ground (-): 
DTC P219E; #3 (E158) No. 9 (+) - Chassis ground (-): 
DTC P219F; #4 (E158) No. 22 (+) - Chassis ground (-): 		 Is the voltage 10 V or more? Repair the short circuit to power in harness between ECM connector and fuel injector connectors. Go to step 25 
25 CHECK FUEL INJECTOR. 
  1. Turn the ignition switch to OFF.
  2. Measure the resistance between fuel injector terminals on faulty cylinder.

Terminals 
No. 1 - No. 2: 		 Is the resistance 5 - 20 Ω? Go to step 26  Replace the faulty fuel injector. Ref. to FUEL INJECTOR
26 CHECK INSTALLATION CONDITION OF CAMSHAFT POSITION SENSOR/CRANKSHAFT POSITION SENSOR.  Is the camshaft position sensor or crankshaft position sensor loosely installed? Tighten the camshaft position sensor or crankshaft position sensor. Ref. to INSTALLATION , Camshaft Position Sensor. Ref. to INSTALLATION , Crankshaft Position Sensor. Go to step 27 
27 CHECK CRANKSHAFT POSITION SENSOR PLATE.  Is the crankshaft position sensor plate rusted or does it have broken teeth? Replace the crankshaft position sensor plate. Ref. to CYLINDER BLOCK Go to step 28 
28 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? Correct the installation condition of timing chain. Ref. To TIMING CHAIN ASSEMBLY Go to step 29 
29 CHECK FUEL LEVEL.  Is the fuel meter indication higher than the "Lower" level? Go to step 30  Refill the fuel so that the fuel meter indication is higher than the "Lower" level, and proceed to the next step. Go to step 30 
30 CHECK STATUS OF MALFUNCTION INDICATOR LIGHT. 
  1. Clear the memory using the Subaru Select Monitor or general scan tool. Ref. to CLEAR MEMORY MODE
  2. Start the engine, and drive the vehicle 10 minutes or more.
 Does the malfunction indicator light illuminate or blink? Go to step 32  Go to step 31 
31 CHECK CAUSE OF MISFIRE.  Was the cause of misfire identified when the engine is running? Finish diagnostics operation, if the engine has no abnormality. 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
32 CHECK AIR INTAKE SYSTEM.  Is there any fault in air intake system? 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?
 Go to step 33 
33 CHECK MISFIRE SYMPTOM. 
  1. Turn the ignition switch to ON.
  2. Check for DTC. Ref. to READ DIAGNOSTIC TROUBLE CODE (DTC)
 Does the Subaru Select Monitor or general scan tool indicate only one DTC? Go to step 36  Go to step 34 
34 CHECK DTC.  Is DTC P0301 and P0303 displayed on the Subaru Select Monitor or general scan tool? Go to step 37  Go to step 35 
35 CHECK DTC.  Is DTC P0302 and P0304 displayed on the Subaru Select Monitor or general scan tool? Go to step 38  . Go to step 39  .
36 ONLY ONE CYLINDER.  Is there any fault in the cylinder? Repair or replace faulty parts.
NOTE: Check the following items.
  • Spark plug
  • Ignition coil
  • Fuel injector
  • Compression
 Go to DTC P0171. Ref. to DTC P0171 SYSTEM TOO LEAN BANK 1 , Diagnostic Procedure with Diagnostic Trouble Code (DTC).
37 GROUP OF #1 AND #3 CYLINDERS  Are there any faults in #1 and #3 cylinders? Repair or replace faulty parts.
NOTE: Check the following items.
  • Spark plug
  • Ignition coil
  • Fuel injector
  • Compression
  • Skipping timing belt teeth
 Go to DTC P0171. Ref. to DTC P0171 SYSTEM TOO LEAN BANK 1 , Diagnostic Procedure with Diagnostic Trouble Code (DTC).
38 GROUP OF #2 AND #4 CYLINDERS  Are there any faults in #2 and #4 cylinders? Repair or replace faulty parts.
NOTE: Check the following items.
  • Spark plug
  • Ignition coil
  • Fuel injector
  • Compression
  • Skipping timing belt teeth
 Go to DTC P0171. Ref. to DTC P0171 SYSTEM TOO LEAN BANK 1 , Diagnostic Procedure with Diagnostic Trouble Code (DTC).
39 CYLINDER AT RANDOM.  Is the engine idle rough? Go to DTC P0171. Ref. to DTC P0171 SYSTEM TOO LEAN BANK 1 , Diagnostic Procedure with Diagnostic Trouble Code (DTC). 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.
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