DTC P1A17: Dc/Dc Converter 2 Boost Command Signal Low: Notes

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Trouble symptom:

When the Auto Start Stop restarts, the audio or navigation system is reset.

Wiring diagram:

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

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ENGINE TYPE FA
Auto Start Stop Ref. 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. Ref. to AUTO START STOP (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .

CHECK DC/DC CONVERTER 2 INSTALLATION .
Based on the model No. label option code, check that the vehicle is equipped with the DC/DC converter 2. Ref. to IDENTIFICATION>MODEL NUMBER LABEL .

NOTE: DC/DC converter 2 is installed on the HK audio (model with audio amplifier) only.

Is it a vehicle equipped with DC/DC converter 2?

Yes: Go to 2.

No: Check the area around the engine control module (ECM) power supply, connector, and engine ground for looseness. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>DIAGNOSTICS WITH PHENOMENON>CHECK POWER SUPPLY AND GROUND LINE OF ENGINE CONTROL MODULE (ECM) . Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>DIAGNOSTICS WITH PHENOMENON>CHECK POWER SUPPLY AND GROUND LINE OF ENGINE CONTROL MODULE (ECM) .
CHECK SYSTEM OPERATION STATUS IN TCM .
1. Using the Subaru Select Monitor, perform the active test [Sub power supply control (ON/OFF Dr.)]. Ref. to AUTO START STOP (DIAGNOSTICS)>ACTIVE TEST .
2. Read the data of [DC/DC Converter 2 Boost Signal Reception] using Subaru Select Monitor. Ref. to AUTO START STOP (DIAGNOSTICS)>DATA MONITOR .
Does the display of [DC/DC Converter 2 Boost Signal Reception] change from [Not yet received] to [Reception] according to the ON/OFF operation?

Yes: 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.

No: Go to 3.
CHECK HARNESS BETWEEN ECM AND DC/DC CONVERTER 2 .
1. Turn the ignition switch to OFF.
2. Disconnect the ECM connector.
3. Disconnect the DC/DC converter 2 connector.
4. Measure the resistance in harness between ECM connector and DC/DC converter 2 connector.
  Connector & terminal
  
  ENGINE TYPE FB
  
  (B62) No. 7 - (i16) No. 3:
  
  ENGINE TYPE FA
  
  (B61) No. 26 - (i16) No. 3:
Is the resistance less than 1 Ω?

Yes: Go to 4.

No: Repair the open circuit in harness between ECM and DC/DC converter 2.
CHECK HARNESS BETWEEN ECM AND DC/DC CONVERTER 2 .
Measure the resistance between ECM connector and chassis ground.

Connector & terminal

ENGINE TYPE FB

(B62) No. 7 - Chassis ground:

ENGINE TYPE FA

(B61) No. 26 - Chassis ground:

Is the resistance 1 MΩ or more?

Yes: Go to 5.

No: Repair the short circuit to ground in harness between ECM and DC/DC converter 2.
CHECK DC/DC BOOST OUTPUT SIGNAL .
1. Connect the ECM connector.
2. Turn the ignition switch to ON.
3. Using the Subaru Select Monitor, perform the active test [Sub power supply control (ON/OFF Dr.)]. Ref. to AUTO START STOP (DIAGNOSTICS)>ACTIVE TEST .
4. Measure the voltage between ECM connector and chassis ground.
  Connector & terminal
  
  ENGINE TYPE FB
  
  (B62) No. 7 (+) - Chassis ground (-):
  
  ENGINE TYPE FA
  
  (B61) No. 26 (+) - Chassis ground (-):
Is the voltage still less than 5 V after ON/OFF operation?

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

No: Check for the poor contact of DC/DC converter 2 connector. Replace the DC/DC converter 2 if no fault is found. Ref. to STARTING/CHARGING SYSTEMS (H4DO)>AUTO START STOP DC/DC CONVERTER . Ref. to STARTING/CHARGING SYSTEMS (H4DOTC)>AUTO START STOP DC/DC CONVERTER .