DTC P1A18: Dc/Dc Converter 2 Boost Command Signal High: Notes

1. -

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Trouble symptom:

Auto Start Stop does not operate.

Wiring diagram:

ENGINE TYPE FB

Auto Start Stop Refer to WIRING SYSTEM>AUTO START STOP>WIRING DIAGRAM>ENGINE TYPE FB .

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ENGINE TYPE FA

Auto Start Stop Refer to WIRING SYSTEM>AUTO START STOP>WIRING DIAGRAM>ENGINE TYPE FA .

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CAUTION:

Use the check board when measuring the ECM terminal voltage and resistance.
After servicing or replacing faulty parts, perform the last step of the basic diagnostic procedure. Refer to AUTO START STOP (DIAGNOSTICS)>Basic Diagnostic Procedure .

CHECK DATA MONITOR .
1. Turn the ignition switch to ON.
2. Read the data of [DC/DC Converter 2 Boost Signal Reception] using Subaru Select Monitor. Refer to AUTO START STOP (DIAGNOSTICS)>Data Monitor .
Is [Reception] displayed in [DC/DC Converter 2 Boost Signal Reception]?

Yes : Go to 2.

No : 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 poor contact of connector, temporary open or short circuit of harness may be the cause.
CHECK DC/DC CONVERTER 2 BOOST COMMAND SIGNAL .
1. Turn the ignition switch to OFF.
2. Disconnect the DC/DC converter 2 connector.
3. Turn the ignition switch to ON.
4. Measure the voltage between DC/DC converter 2 connector and chassis ground.
  Connector & terminal
  
  (i16) No. 3 (+) - Chassis ground (-):
Is the voltage 5 V or more?

Yes : Go to 3.

No : Repair the poor contact of DC/DC converter 2 connector. Replace the DC/DC converter 2 if defective. Refer to STARTING/CHARGING SYSTEMS (H4DO)>AUTO START STOP DC/DC CONVERTER . Refer to STARTING/CHARGING SYSTEMS (H4DOTC)>AUTO START STOP DC/DC CONVERTER .
CHECK HARNESS BETWEEN ECM AND DC/DC CONVERTER 2 .
1. Turn the ignition switch to OFF.
2. Disconnect the ECM connector.
3. Turn the ignition switch to ON.
4. Measure the voltage between ECM connector and chassis ground.
  Connector & terminal
  
  ENGINE TYPE FB
  
  (B62) No. 7 (+) - Chassis ground (-):
  
  ENGINE TYPE FA
  
  (E51) No. 23 (+) - Chassis ground (-):
Is the voltage 5 V or more?

Yes : Repair the short circuit to power supply in harness between ECM and DC/DC converter 2.

No : Check for poor contact of ECM connector. Replace the ECM if no fault is found. Refer to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>ENGINE CONTROL MODULE (ECM) . Refer to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>ENGINE CONTROL MODULE (ECM) .