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

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DTC B1207:86 [ELECTRICAL SUPPLY UNIT (ESU)]

Description	Error signal received from SAS control module
Detection condition	The electrical supply unit (ESU) detected the following conditions for 2 s or more with the ignition switched ON (engine off or on). Error signal is received from SAS control module even though the collision detection unlock function presence signal received from the BCM determines that the function is present.
Fail-safe	Not applicable
Possible cause	SAS control module connector or terminal malfunction Electrical supply unit (ESU) connector or terminal malfunction Short to ground in wiring harness between SAS control module terminal 3X and electrical supply unit (ESU) terminal 2H Short to power supply in wiring harness between SAS control module terminal 3X and electrical supply unit (ESU) terminal 2H Open circuit in wiring harness between SAS control module terminal 3X and electrical supply unit (ESU) terminal 2H SAS control module malfunction Electrical supply unit (ESU) malfunction

Diagnostic Procedure

Step	Inspection		Action
1	INSPECT SAS CONTROL MODULE CONNECTOR CONDITION Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.) Disconnect the SAS control module 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 7.
2	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 7.
3	INSPECT WIRING HARNESS BETWEEN SAS CONTROL MODULE AND ELECTRICAL SUPPLY UNIT (ESU) FOR SHORT TO GROUND Verify that the SAS control module and electrical supply unit (ESU) connectors are disconnected. Inspect for continuity between SAS control module terminal 3X (wiring harness-side) and body ground. Is there continuity?	Yes	Refer to the wiring diagram and verify whether or not there is a common connector between SAS control module terminal 3X and electrical supply unit (ESU) terminal 2H. 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 a short to ground. Repair or replace the malfunctioning part. If there is no common connector: Repair or replace the wiring harness which has a short to ground. Go to Step 7.
		No	Go to the next step.
4	INSPECT WIRING HARNESS BETWEEN SAS CONTROL MODULE AND ELECTRICAL SUPPLY UNIT (ESU) FOR SHORT TO POWER SUPPLY Verify that the SAS control module and electrical supply unit (ESU) connectors are disconnected. Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.) Switch the ignition ON (engine off or on). Measure the voltage at the SAS control module terminal 3X (wiring harness-side). Is the voltage 0 V?	Yes	Go to the next step.
		No	Refer to the wiring diagram and verify whether or not there is a common connector between SAS control module terminal 3X and electrical supply unit (ESU) terminal 2H. 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 a short to power supply. Repair or replace the malfunctioning part. If there is no common connector: Repair or replace the wiring harness which has a short to power supply. Go to Step 7.
5	INSPECT WIRING HARNESS BETWEEN SAS CONTROL MODULE AND ELECTRICAL SUPPLY UNIT (ESU) FOR OPEN CIRCUIT Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.) Verify that the SAS control module and electrical supply unit (ESU) connectors are disconnected. Inspect the wiring harness for continuity between SAS control module terminal 3X (wiring harness-side) and electrical supply unit (ESU) terminal 2H (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 SAS control module terminal 3X and electrical supply unit (ESU) terminal 2H. 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 7.
6	VERIFY IF MALFUNCTIONING LOCATION IS SAS CONTROL MODULE DEPENDING ON REPEATABILITY 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)].) Switch the ignition ON (engine off or on) and wait for 2 s or more. Retrieve the electrical supply unit (ESU) DTCs using the M-MDS. (See DTC INSPECTION [ELECTRICAL SUPPLY UNIT (ESU)].) Is the same DTC displayed?	Yes	Replace the SAS control module, then go to the next step. (See SAS CONTROL MODULE REMOVAL/INSTALLATION [STANDARD DEPLOYMENT CONTROL SYSTEM].) (See SAS CONTROL MODULE REMOVAL/INSTALLATION [TWO-STEP DEPLOYMENT CONTROL SYSTEM].)
		No	Go to Step 8.
7	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)].) Switch the ignition ON (engine off or on) and wait for 2 s or more. 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.
8	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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