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:

Auto Start Stop does not operate.
When the Auto Start Stop restarts, the audio or navigation system is reset.

Wiring diagram:

Auto Start Stop Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>AUTO START STOP .

Courtesy of SUBARU OF AMERICA, INC.

CHECK DC/DC CONVERTER 2 INSTALLATION .
Based on the model number label option code, check if the vehicle is equipped with the DC/DC converter 2. Ref. to IDENTIFICATION>MODEL NUMBER LABEL>OPTION CODE .

NOTE: DC/DC converter 2 is only for vehicles equipped with Harman/Kardon audio.

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

Yes: Go to 2.

No: Check the ECM power supply area. Check if the connectors and engine ground are attached without looseness. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.5)>DIAGNOSTICS WITH PHENOMENON>CHECK POWER SUPPLY AND GROUND LINE OF ENGINE CONTROL MODULE (ECM) . Ref. to ENGINE (DIAGNOSTICS) (H4DO (HEV))>DIAGNOSTICS WITH PHENOMENON>CHECK POWER SUPPLY AND GROUND LINE OF ENGINE CONTROL MODULE (ECM) . Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>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 Received 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
  
  (B134) No. 7 - (B630) 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

(B134) No. 7 - 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
  
  (B134) No. 7 (+) - 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 (EXCEPT FOR HEV))>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 (EXCEPT FOR HEV))>AUTO START STOP DC/DC CONVERTER .