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

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DTC B108F:16 [BCM]

Description	Door lock switch circuit malfunction
Detection condition	With the door lock switch off, the BCM detects a short to ground in the door lock switch circuit.
Fail-safe	Not applicable
Possible cause	Door lock switch (LH) connector or terminal malfunction Door lock switch (RH) connector or terminal malfunction Door lock switch (LH) malfunction Door lock switch (RH) malfunction BCM connector or terminal malfunction Short to ground in wiring harness between the following terminals: Door lock switch (LH) terminal 2I—BCM terminal 2K Door lock switch (RH) terminal C—BCM terminal 2K BCM malfunction

Diagnostic Procedure

Step	Inspection		Action
1	VERIFY BCM DTCs AGAIN Clear the DTC for the BCM using the M-MDS. (See CLEARING DTC [BCM].) Retrieve the BCM DTCs using the M-MDS. (See DTC INSPECTION [BCM].) Is the same DTC displayed?	Yes	Go to the next step.
		No	Go to Step 9.
2	INSPECT DOOR LOCK SWITCH (LH) CONNECTOR CONDITION Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.) Disconnect the door lock switch (LH) 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 8.
3	INSPECT DOOR LOCK SWITCH (RH) CONNECTOR CONDITION Disconnect the door lock switch (RH) 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 8.
4	INSPECT DOOR LOCK SWITCH (LH) Inspect the door lock switch (LH). (See DOOR LOCK SWITCH INSPECTION.) Is the door lock switch (LH) normal?	Yes	Go to the next step.
		No	Replace the door lock switch (LH), then go to Step 8. (See DOOR LOCK SWITCH REMOVAL/INSTALLATION.)
5	INSPECT DOOR LOCK SWITCH (RH) Inspect the door lock switch (RH). (See DOOR LOCK SWITCH INSPECTION.) Is the door lock switch (RH) normal?	Yes	Go to the next step.
		No	Replace the door lock switch (RH), then go to Step 8. (See DOOR LOCK SWITCH REMOVAL/INSTALLATION.)
6	INSPECT BCM CONNECTOR CONDITION Disconnect the BCM 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 8.
7	INSPECT DOOR LOCK SWITCH CIRCUIT FOR SHORT TO GROUND Verify that the door lock switch (LH), door lock switch (RH) and BCM connectors are disconnected. Inspect for continuity between BCM terminal 2K (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 the following terminals: Door lock switch (LH) terminal 2I—BCM terminal 2K Door lock switch (RH) terminal C—BCM terminal 2K 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 the next step.
		No	Go to the next step.
8	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 BCM using the M-MDS. (See CLEARING DTC [BCM].) Retrieve the BCM DTCs using the M-MDS. (See DTC INSPECTION [BCM].) Is the same DTC displayed?	Yes	Repeat the inspection from Step 1. If the malfunction recurs, replace the BCM. (See BODY CONTROL MODULE (BCM) REMOVAL/INSTALLATION.) Go to the next step.
		No	Go to the next step.
9	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 [BCM].)
		No	DTC troubleshooting completed.

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