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

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DTC B1D35:86 [BCM]

Description	Hazard warning switch error signal received
Detection condition	BCM receives the error signals from the start stop unit for 2 s or more with the ignition switched ON (engine off or on).
Fail-safe	Perform the control with hazard warning switch signal turned off.
Possible cause	Start stop unit malfunction Hazard warning switch malfunction BCM malfunction
System wiring diagram	Not applicable

Diagnostic Procedure

Step	Inspection		Action
1	VERIFY BCM DTCs AGAIN Clear the DTC for the BCM using the M-MDS. (See CLEARING DTC [BCM].) Switch the ignition ON (engine off or on) and wait for 2 s or more. 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 6.
2	DETERMINE MALFUNCTIONING LOCATION BY PERFORMING PID/DATA MONITOR INSPECTION Using the M-MDS, display PID HAZARD_SW for the start stop unit. (See PID/DATA MONITOR INSPECTION [START STOP UNIT].) Does the PID monitoring value switch correctly according to the hazard warning switch operation?	Yes	Go to Step 4. (Circuit between hazard warning switch and start stop unit is normal)
		No	Go to the next step.
3	INSPECT HAZARD WARNING SWITCH Inspect the hazard warning switch. (See HAZARD WARNING SWITCH INSPECTION.) Is the hazard warning switch normal?	Yes	Replace the start stop unit, then go to Step 5. (See START STOP UNIT REMOVAL/INSTALLATION.)
		No	Replace the hazard warning switch, then go to Step 5. (See HAZARD WARNING SWITCH REMOVAL/INSTALLATION.)
4	DETERMINE MALFUNCTIONING LOCATION BY PERFORMING PID/DATA MONITOR INSPECTION Using the M-MDS, display PID HAZARD_SW for the BCM. (See PID/DATA MONITOR INSPECTION [BCM].) Does the PID monitoring value switch correctly according to the hazard warning switch operation?	Yes	Go to the next step. (Circuit between start stop unit and BCM is normal)
		No	Replace the start stop unit, then go to the next step. (See START STOP UNIT REMOVAL/INSTALLATION.)
5	VERIFY THAT REPAIRS HAVE BEEN COMPLETED Clear the DTC for the BCM using the M-MDS. (See CLEARING DTC [BCM].) Switch the ignition ON (engine off or on) and wait for 2 s or more. 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.
6	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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