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

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DTC B1048:7B [BCM]

Description	Brake fluid level sensor circuit malfunction
Detection condition	BCM detected that the brake fluid level is less than MIN with the ignition switched ON (engine off or on).
Fail-safe	Not applicable
Possible cause	Insufficient brake fluid level Brake fluid level sensor connector or terminal malfunction BCM connector or terminal malfunction Short to ground in wiring harness between brake fluid level sensor terminal A and BCM terminal 3R Brake fluid level sensor malfunction 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 8.
2	INSPECT BRAKE FLUID LEVEL Inspect the brake fluid level. (See BRAKE FLUID INSPECTION.) Is the brake fluid level normal?	Yes	Go to the next step.
		No	Add genuine brake fluid, then go to Step 7.
3	INSPECT BRAKE FLUID LEVEL SENSOR CONNECTOR CONDITION Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.) Disconnect the brake fluid level sensor 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.
4	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 7.
5	INSPECT BRAKE FLUID LEVEL SENSOR SIGNAL CIRCUIT FOR SHORT TO GROUND Verify that the brake fluid level sensor and BCM connectors are disconnected. Inspect for continuity between BCM terminal 3R (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 brake fluid level sensor terminal A and BCM terminal 3R. 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.
6	INSPECT BRAKE FLUID LEVEL SENSOR Inspect the brake fluid level sensor. (See BRAKE FLUID LEVEL SENSOR INSPECTION.) Is the brake fluid level sensor normal?	Yes	Go to the next step.
		No	Replace the brake fluid level sensor, then go to the next step. (See MASTER CYLINDER REMOVAL/INSTALLATION.)
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 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.
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 [BCM].)
		No	DTC troubleshooting completed.

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