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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5

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DTC B1C79:13 [ELECTRICAL SUPPLY UNIT (ESU)]

Description	Washer motor circuit malfunction
Detection condition	Electrical supply unit (ESU) detects an open circuit in the washer motor circuit with the ignition switched ON (engine off or on).
Fail-safe	Not applicable
Possible cause	Washer motor connector or terminal malfunction Open circuit in wiring harness between washer motor terminal A and body ground Washer motor malfunction Electrical supply unit (ESU) connector or terminal malfunction Open circuit in wiring harness between washer motor terminal B and electrical supply unit (ESU) terminal 4B Electrical supply unit (ESU) malfunction

Diagnostic Procedure

Step	Inspection		Action
1	INSPECT WASHER MOTOR CONNECTOR CONDITION Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.) Disconnect the washer motor connector. Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection. Is the connector normal?	Yes	Go to the next step.
		No	Repair or replace the connector, then go to Step 6.
2	INSPECT WASHER MOTOR GROUND CIRCUIT FOR OPEN CIRCUIT Verify that the washer motor connector is disconnected. Inspect for continuity between washer motor terminal A (wiring harness-side) and body ground. Is there continuity?	Yes	Go to the next step.
		No	Refer to the wiring diagram and verify whether or not there is a common connector between washer motor terminal A and body ground. If there is a common connector: Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit. Repair or replace the malfunctioning part. If there is no common connector: Repair or replace the wiring harness which has an open circuit. Go to Step 6.
3	INSPECT WASHER MOTOR Inspect the washer motor. (See WASHER MOTOR INSPECTION.) Is the washer motor normal?	Yes	Go to the next step.
		No	Replace the washer motor, then go to Step 6. (See WASHER MOTOR REMOVAL/INSTALLATION.)
4	INSPECT ELECTRICAL SUPPLY UNIT (ESU) CONNECTOR CONDITION Disconnect the electrical supply unit (ESU) connector. Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection. Is the connector normal?	Yes	Go to the next step.
		No	Repair or replace the connector, then go to Step 6.
5	INSPECT WASHER MOTOR CIRCUIT FOR OPEN CIRCUIT Verify that the washer motor and electrical supply unit (ESU) connectors are disconnected. Inspect for continuity between washer motor terminal B (wiring harness-side) and electrical supply unit (ESU) terminal 4B (wiring harness-side). Is there continuity?	Yes	Go to the next step.
		No	Refer to the wiring diagram and verify whether or not there is a common connector between washer motor terminal B and electrical supply unit (ESU) terminal 4B. If there is a common connector: Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit. Repair or replace the malfunctioning part. If there is no common connector: Repair or replace the wiring harness which has an open circuit. Go to the next step.
6	VERIFY THAT REPAIRS HAVE BEEN COMPLETED Always reconnect all disconnected connectors. Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.) Clear the DTC for the electrical supply unit (ESU) using the M-MDS. (See CLEARING DTC [ELECTRICAL SUPPLY UNIT (ESU)].) Operate the washer switch to ON position. Retrieve the electrical supply unit (ESU) DTCs using the M-MDS. (See DTC INSPECTION [ELECTRICAL SUPPLY UNIT (ESU)].) Is the same DTC displayed?	Yes	Repeat the inspection from Step 1. If the malfunction recurs, replace the electrical supply unit (ESU). (See ELECTRICAL SUPPLY UNIT (ESU) REMOVAL/INSTALLATION.) Go to the next step.
		No	Go to the next step.
7	VERIFY IF OTHER DTCs DISPLAYED Are any other DTCs displayed?	Yes	Repair or replace the malfunctioning part according to the applicable DTC troubleshooting. (See DTC TABLE [ELECTRICAL SUPPLY UNIT (ESU)].)
		No	DTC troubleshooting completed.

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