DTC P1235: High Pressure Fuel Pump Circuit: Notes

1. -

DTC detecting condition:

Immediately at fault recognition

Trouble symptom:

Improper idling
Poor driving performance

Wiring diagram:

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

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>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)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

CHECK HIGH-PRESSURE FUEL PUMP.
1. Turn the ignition switch to OFF.
2. Check the high-pressure fuel pump. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>HIGH PRESSURE FUEL PUMP>INSPECTION .
Is the check result OK?

Yes: Go to 2.

No: Replace the high-pressure fuel pump. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>HIGH PRESSURE FUEL PUMP .
CHECK HARNESS BETWEEN ECM AND HIGH-PRESSURE FUEL PUMP CONNECTOR (OPEN).
1. Disconnect the connector from ECM.
2. Disconnect the connector from high-pressure fuel pump.
3. Measure the resistance of harness between ECM connector and high-pressure fuel pump connector.
  Connector & terminal
  
  (E158) No. 105 - (E160) No. 2:
  
  (E158) No. 114 - (E160) No. 1:
Is the resistance less than 1 Ω?

Yes: Go to 3.

No: Repair the open circuit in harness between ECM connector and high-pressure fuel pump connector.
CHECK HARNESS BETWEEN ECM AND HIGH-PRESSURE FUEL PUMP CONNECTOR (SHORT TO GROUND).
Measure the resistance between the ECM connector and engine ground.

Connector & terminal

(E158) No. 105 - Engine ground:

(E158) No. 114 - 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 high-pressure fuel pump connector.
CHECK HARNESS BETWEEN ECM AND HIGH-PRESSURE FUEL PUMP CONNECTOR (SHORT TO POWER SUPPLY).
Measure the voltage between high-pressure fuel pump connector and engine ground.

Connector & terminal

(E160) No. 1 (+) - Engine ground (-):

Is the voltage 10 V or more?

Yes: Repair the short circuit to power supply in harness between ECM connector and high-pressure fuel pump connector.

No: Go to 5.
CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.

Is there poor contact of ECM connector?

Yes: Repair the poor contact of ECM connector.

No: Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>ENGINE CONTROL MODULE (ECM) .