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 .

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.

C onnector & 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) .