DTC P1378: Pre-Ignition Detected: Notes

-
DTC detecting condition:

Immediately at fault recognition

Wiring diagram:

Engine Electrical System. Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

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) (H4DOTC)>General Description>PREPARATION TOOL>HOW TO USE CHECK BOARD .
NOTE:
- This DTC may be detected even if fault does not occur in the vehicle. If the customer does not ask for inspection, clear memory instead of inspection and return the vehicle to the user. Ref. to COMMON (diag)>CLEAR MEMORY .
- After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Basic Diagnostic Procedure>PROCEDURE .

CHECK DTC .
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 DTC other than P1378 displayed? (Current malfunction)
  
  Yes : Check the appropriate DTC using the "Diagnostic Trouble Code (DTC)". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Diagnostic Trouble Code (DTC)>LIST .
  
  No : Go to 2.
CHECK PHENOMENON .
For the result of the interview, check the problem of the following symptoms.
- Engine startability
- Rough idling
- Misfire or insufficient power
- Other symptom
Can the malfunction symptom be confirmed?

Yes : Perform the diagnosis according to the phenomenon.

No : Go to 3.
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) .

Is DTC P1378 displayed? (Current malfunction)

Yes : Go to 4.

No : Even if DTC is detected, it has returned to a normal condition at this time.
CHECK FREEZE FRAME DATA .
Using the Subaru Select Monitor or a general scan tool, read the freeze frame data of [Engine]. Ref. to COMMON (diag)>FREEZE FRAME DATA .

Is [Number of Pre-Ignition Control (Detection) Operating] 1 or more?

Yes : Go to 5.

No : Go to 16.
CHECK IGNITION TIMING .
1. Warm up the engine.
2. Fix the ignition timing to BTDC10° by selecting the [Fixed Idle Ignition Timing] in [Active Test] using Subaru Select Monitor.
  NOTE: For detailed operation procedures, refer to the "Active Test". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>ACTIVE TEST .
3. Using the timing light, check the actual ignition timing at BTDC 10°.
  Does the ignition timing match?
  
  Yes : Go to 6.
  
  No : Go to 11.
CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .
1. Turn the ignition switch to OFF.
2. Remove the mass air flow and intake air temperature sensor from the vehicle, and cool down to the compartment temperature. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>MASS AIR FLOWS AND INTAKE AIR TEMPERATURE SENSOR .
3. Connect the mass air flow and intake air temperature sensor.
4. Turn the ignition switch to ON.
5. Using the Subaru Select Monitor, read the value in [Intake Air Temperature (B1-S1)].
  NOTE: For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (diag)>DATA MONITOR .
  
  Do the compartment temperature and the temperature displayed in "Data Monitor" match?
  
  Yes : Go to 11.
  
  No : Go to 7.
CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .
Check the mass air flow and intake air temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>Mass Air Flow and Intake Air Temperature Sensor>INSPECTION .

Is the check result OK?

Yes : Go to 8.

No : Replace the mass air flow and intake air temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>MASS AIR FLOWS AND INTAKE AIR TEMPERATURE SENSOR . Go to 34.
CHECK HARNESS BETWEEN ECM AND MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR (OPEN) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Disconnect the connectors from the mass air flow and intake air temperature sensor.
4. Measure the resistance of harness between ECM connector and the mass air flow and intake air temperature sensor connector.
  Connector & terminal
  
  (B134) No. 62 - (B3) No. 2:
  
  (B134) No. 3 - (B3) No. 4:
  
  Is the resistance less than 1 Ω?
  
  Yes : Go to 9.
  
  No : Repair the open circuit of harness between ECM connector and the mass air flow and intake air temperature sensor connector. Go to 34.
CHECK HARNESS BETWEEN ECM AND THE MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR (SHORT TO GROUND) .
Measure the resistance between the ECM connector and engine ground.

Connector & terminal

(B134) No. 3 - Engine ground:

Is the resistance 1 MΩ or more?

Yes : Go to 10.

No : Repair the ground short circuit of harness between ECM connector and the mass air flow and intake air temperature sensor connector. Go to 34.
CHECK HARNESS BETWEEN ECM AND MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR (LINE-TO-LINE SHORT) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Disconnect the connectors from the mass air flow and intake air temperature sensor.
4. Measure the resistance of harness between ECM connector and the mass air flow and intake air temperature sensor connector.
  Connector & terminal
  
  (B3) No. 2 - (B3) No. 4:
  
  Is the resistance 1 MΩ or more?
  
  Yes : Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>ENGINE CONTROL MODULE (ECM) .
  
  No : Repair the line-to-line short circuit of harness between ECM connector and the mass air flow and intake air temperature sensor connector. Go to 34.
CHECK CRANKSHAFT POSITION SENSOR, INTAKE CAMSHAFT POSITION SENSOR .
1. Using SST and an oscilloscope, measure waveform of crankshaft position sensor and camshaft position sensor.
2. Check if "Number of signals for every two crankshaft revolutions", "Phase difference of the crankshaft position sensor and intake camshaft position sensor signals", "Signal waveform" match according to the sample waveform described in the information.
  Is the check result OK?
  
  Yes : Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>ENGINE CONTROL MODULE (ECM) . Go to 14.
  
  No : Correct the displacement of the timing chain. Go to 12.
CHECK CRANKSHAFT POSITION SENSOR WAVEFORM .
Check the number of signals and presence/absence of noise with waveform of the crankshaft position sensor.

Is the check result OK?

Yes : Go to 13.

No : Perform the diagnosis of DTC P0335 CRANKSHAFT POSITION SENSOR "A" CIRCUIT. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Diagnostic Procedure with Diagnostic Trouble Code (DTC)>DTC P0335 CRANKSHAFT POSITION SENSOR "A" CIRCUIT . Go to 14.
CHECK CAMSHAFT POSITION SENSOR WAVEFORM .
Check the number of signals and presence/absence of noise with waveform of the camshaft position sensor.

Is the check result OK?

Yes : Go to 15.

No : Perform the diagnosis for DTC P0340 CAMSHAFT POSITION SENSOR "A" CIRCUIT

BANK 1 OR SINGLE SENSOR and DTC P0345 CAMSHAFT POSITION SENSOR "A" CIRCUIT BANK 2. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Diagnostic Procedure with Diagnostic Trouble Code (DTC)>DTC P0340 CAMSHAFT POSITION SENSOR "A" CIRCUIT BANK 1 OR SINGLE SENSOR . Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Diagnostic Procedure with Diagnostic Trouble Code (DTC)>DTC P0345 CAMSHAFT POSITION SENSOR "A" CIRCUIT BANK 2 . Go to 15.
CHECK DTC .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor or a general scan tool, perform the clear memory of [Engine]. Ref. to COMMON (diag)>CLEAR MEMORY .
3. Perform the reproduction test.
4. Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (diag)>DIAGNOSTIC TROUBLE CODE (DTC) .
  Is DTC P1378 displayed? (Current malfunction)
  
  Yes : Go to 15.
  
  No : Currently, it is normal.
CHECK ENGINE OIL .
Check the engine oil. Ref. to LUBRICATION (H4DOTC)>Engine Oil>INSPECTION .

Is the check result OK?

Yes : Go to 16.

No : Replace engine oil. Ref. to LUBRICATION (H4DOTC)>Engine Oil>REPLACEMENT . Go to 16.
CHECK COOLANT .
Check the coolant. Ref. to COOLING (H4DOTC)>Engine Coolant>INSPECTION .

Is the check result OK?

Yes : Go to 17.

No : Perform replacement and bleeding of the coolant. Ref. to COOLING (H4DOTC)>Engine Coolant>REPLACEMENT . Go to 17.
CHECK RADIATOR FAN .
1. Using the Subaru Select Monitor, select [Radiator Fan Relay] of [Active Test].
  NOTE: For detailed operation procedures, refer to the "Active Test". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>ACTIVE TEST .
2. Check operation/stop of the radiator fan according to ON/OFF switching operation.
  Is the check result OK?
  
  Yes : Go to 18.
  
  No : Check the radiator fan operation. Ref. to COOLING (H4DOTC)>RADIATOR FAN SYSTEM . Go to 18.
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 : Go to 19.

No : Repair or replace the air intake system. Go to 19.
CHECK FRONT OXYGEN (A/F) SENSOR DATA .
1. Start the engine and warm up completely.
2. Raise the engine speed up to 2, 500 rpm and maintain it for approx. three minutes.
3. Release the accelerator pedal and idle the engine.
4. Using the Subaru Select Monitor, select [Injection quantity Control] in [Active Test], and read the value of [A/F Sensor #1] at the increase rate of both 12% and -12%.
  NOTE:
  - Perform the operation immediately after the engine comes into idling condition, otherwise the front oxygen (A/F) sensor will be cooled.
  - For detailed operation procedures, refer to the "Active Test". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>ACTIVE TEST .
  - The value of [A/F Sensor #1] will change to 0.93 or 1.17 when [Injection quantity Control] in [Active Test] is changed between -12% - +12% with [Long Term Fuel Trim (B1)] at -5%.
  Does the value of [A/F Sensor #1] change to less than 0.88 at the increase rate of 12%, and to 1.12 or more at the rate of -12%?
  
  Yes : Go to 33.
  
  No : Go to 20.
CHECK POWER SUPPLY OF FRONT OXYGEN (A/F) SENSOR .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from the front oxygen (A/F) sensor.
3. Turn the ignition switch to ON.
4. Measure the voltage between front oxygen (A/F) sensor connector and engine ground.
  Connector & terminal
  
  (E24) No. 3 (+) - Engine ground (-):
  
  Is the voltage 10 V or more?
  
  Yes : Go to 21.
  
  No : Repair or replace the power supply circuit. Go to 33.
  NOTE:
  In this case, repair the following item:
  - Open circuit in harness between M/B and front oxygen (A/F) sensor connector
  - Poor contact of J/C
  - Poor contact of coupling connector
  - Blown out of fuse
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. Measure the resistance of harness between ECM connector and front oxygen (A/F) sensor connector.
  Connector & terminal
  
  (E158) No. 43 - (E24) No. 1:
  
  (E158) No. 56 - (E24) No. 4:
  
  (E158) No. 44 - (E24) No. 5:
  
  Is the resistance less than 1 Ω?
  
  Yes : Go to 22.
  
  No : Repair the open circuit of harness or replace the harness between ECM connector and front oxygen (A/F) sensor connector. Go to 33.
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. 43 (+) - Engine ground (-):

(E158) No. 56 (+) - Engine ground (-):

(E158) No. 44 (+) - Engine ground (-):

Is the resistance 1 MΩ or more?

Yes : Go to 23.

No : Repair the short circuit to ground in harness or replace the harness between ECM connector and front oxygen (A/F) sensor connector. Go to 33.
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.
Measure the fuel pressure. Ref. to MECHANICAL (H4DOTC)>FUEL PRESSURE .

NOTE: If the indication of the fuel pressure gauge is not stable, read the mean value of the indication.

Is the measured value 340 - 400 kPa (3.5 - 4.1 kgf/cm² , 49 - 58 psi)?

Yes : Go to 26.

No : Check the fuel delivery line. Go to 24.
CHECK OF FUEL PUMP .
Using the Subaru Select Monitor, select [Fuel Pump Relay] of [Active Test] to operate the fuel pump.

NOTE: For detailed operation procedures, refer to the "Active Test". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>ACTIVE TEST .

Does the fuel pump emit operating sound?

Yes : Go to 26.

No : Go to 25.
CHECK OF FUEL PUMP .
Check fuel pump. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>Fuel Pump>INSPECTION .

Is the check result OK?

Yes : Repair the wiring malfunction of the fuel pump. Go to 26.

No : Replace the fuel pump. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>FUEL PUMP . Go to 26.
CHECK FUEL TANK .
WARNING: Place "NO OPEN FLAMES" signs near the working area.

Check if any foreign matters such as iron powder exist in the fuel tank.

Is there any foreign matter in the fuel tank?

Yes : Remove foreign matter from the fuel tank. Go to 33.

No : Go to 27.
CHECK FREEZE FRAME DATA .
Using the Subaru Select Monitor, read the values in [Fuel Rail Pressure A] and [Commanded Fuel Rail Pressure A].

NOTE: For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (diag)>FREEZE FRAME DATA .

Is the value in [Fuel Rail Pressure A] synchronized with the one in [Commanded Fuel Rail Pressure A] in all freeze frame data?

Yes : Go to 28.

No : Check the high-pressure fuel pump, and if any fault is found, replace the high-pressure fuel pump. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>HIGH PRESSURE FUEL PUMP . Go to 33.
CHECK KNOCK SENSOR .
1. Warm up and then idle the engine.
2. Using the Subaru Select Monitor, read the value in [Knocking Signal].
  NOTE: For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (diag)>DATA MONITOR .
  
  Is the value of [Knocking Signal] [ON]?
  
  Yes : Go to 29.
  
  No : Go to 30.
CHECK KNOCK SENSOR .
Check the knock sensor signals using oscilloscope.

Does noise occur in the knocking sensor signals?

Yes : Repair the noise cause.

No : Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>ENGINE CONTROL MODULE (ECM) .
CHECK SPARK PLUG .
Check the spark plug. Ref. to IGNITION (H4DOTC)>SPARK PLUG .

Is the check result OK?

Yes : Go to 31.

No : Replace all spark plugs on all cylinders. Ref. to IGNITION (H4DOTC)>SPARK PLUG . Go to 31.
CHECK COMPRESSION PRESSURE .
Check the compression pressure. Ref. to MECHANICAL (H4DOTC)>COMPRESSION .

Is the check result OK?

Yes : Go to 32.

No : Check compression failure of the engine unit. Go to 32.
CHECK FUEL INJECTOR .
1. Remove the fuel injector. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>Fuel Injector>REMOVAL
2. Check fuel injector.
  Is there any deposit in the tip of fuel injector?
  
  Yes : Replace the fuel injector. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>FUEL INJECTOR .
  
  Remove foreign objects such as carbon adhered inside the combustion chamber. Go to 33.
  
  No : Go to 33.
CHECK DTC .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor or a general scan tool, perform the clear memory of [Engine]. Ref. to COMMON (diag)>CLEAR MEMORY .
3. Perform the reproduction test.
4. Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (diag)>DIAGNOSTIC TROUBLE CODE (DTC) .
  Is DTC P1378 displayed? (Current malfunction)
  
  Yes : Go to 34.
  
  No : Currently, it is normal.
CHECK DTC .
1. Turn the ignition switch to OFF.
2. Replace the entire fuel.
3. Turn the ignition switch to ON.
4. Using the Subaru Select Monitor or a general scan tool, perform the clear memory of [Engine]. Ref. to COMMON (diag)>CLEAR MEMORY .
5. Perform the reproduction test.
6. Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (diag)>DIAGNOSTIC TROUBLE CODE (DTC) .
  Is DTC P1378 displayed? (Current malfunction)
  
  Yes : Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>ENGINE CONTROL MODULE (ECM) .
  
  No : Currently, it is normal.