DTC P1235: High Pressure Fuel Pump Circuit: Notes

-
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 .
1. 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 .
2. 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.
3. 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.
4. 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.
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) .