Subaru Legacy BN/BS (2015-2019) Service Manual: Dtc c1571 brake lamp relay off stuck

Subaru Legacy BN/BS (2015-2019) Service Manual / Vehicle dynamics control (vdc) (diagnostics) / Diagnostic procedure with diagnostic trouble code (dtc) / Dtc c1571 brake lamp relay off stuck

DTC DETECTING CONDITION:

A fault is detected if the stop light relay operation request were compared with the feedback signal and detected as follows:

• The feedback signal is OFF.

• The stop light relay operation request is ON.

TROUBLE SYMPTOM:

• EyeSight does not operate. (Models with EyeSight)

• Stop lights do not illuminate sometimes.

WIRING DIAGRAM:

Vehicle dynamics control system Vehicle Dynamics Control System

STEP	CHECK	YES	NO
1.CHECK DTC. Check the DTC using Subaru Select Monitor. Read Diagnostic Trouble Code (DTC)	Are any DTCs related to the stop light switch displayed-	Perform the diagnosis according to DTC. List of Diagnostic Trouble Code (DTC)	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC C1571 BRAKE LAMP RELAY OFF STUCK
2.CHECK STOP LIGHT RELAY. 1) Turn the ignition switch to OFF. 2) Remove the stop light relay. 3) Measure the resistance between stop light relay terminals No. 13 — No. 11 when the battery voltage is applied. Terminals No. 14 — No. 15:	Is the resistance less than 1 --	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC C1571 BRAKE LAMP RELAY OFF STUCK	Replace the stop light relay.
3.CHECK VDCCM&H/U CONNECTOR. Disconnect the connector from the VDCCM&H/U.	Is there poor contact or damage of the VDCCM&H/U connector-	Repair the VDCCM&H/U connector.	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC C1571 BRAKE LAMP RELAY OFF STUCK
4.CHECK STOP LIGHT SWITCH CIRCUIT. Measure the resistance between the stop light relay and the fuse. Connector & terminal (B48) No. 14 — (F/B fuse) No. 37:	Is the resistance less than 1 --	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC C1571 BRAKE LAMP RELAY OFF STUCK	Repair the stop light switch circuit.
5.CHECK STOP LIGHT SWITCH CIRCUIT. 1) Connect all connectors. 2) Turn the ignition switch to ON. 3) Measure the voltage between stop light relay and chassis ground. Connector & terminal (B48) No. 14 (+) — Chassis ground (−):	Is the voltage 10 V or more-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC C1571 BRAKE LAMP RELAY OFF STUCK	Repair the stop light switch circuit.
6.CHECK STOP LIGHT RELAY CIRCUIT. 1) Turn the ignition switch to OFF. 2) Remove the stop light relay. 3) Turn the ignition switch to ON. 4) Measure the voltage between stop light relay and chassis ground. Connector & terminal (B48) No. 13 (+) — Chassis ground (−):	Is the voltage 10 V or more-	Repair the stop light relay circuit.	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC C1571 BRAKE LAMP RELAY OFF STUCK
7.CHECK VDCCM&H/U. 1) Turn the ignition switch to OFF. 2) Connect all connectors and relays. 3) Perform the Clear Memory Mode. Clear Memory Mode 4) Read the DTC. Read Diagnostic Trouble Code (DTC)	Is the same DTC displayed-	Replace the VDCCM&H/U. VDC Control Module and Hydraulic Control Unit (VDCCM&H/U)	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC C1571 BRAKE LAMP RELAY OFF STUCK
8.CHECK DETECTION OF OTHER DTCS FOR VDC. Read Diagnostic Trouble Code (DTC)	Is any other DTC displayed-	Perform the diagnosis according to DTC. List of Diagnostic Trouble Code (DTC)	Currently, it is normal. There may have been a poor contact in the harness and connector or a temporarily noise interference.

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Other materials:

Control unit note
System control of the EyeSight is performed by each module. For procedure, refer to the following sections.• Engine control module (ECM)– H4 model: Engine Control Module (ECM)– H6 model: Engine Control Module (ECM)• Transmission control module (TCM)– H4 model: Transmission Co ...