Diagnostic procedure

WARNING: This page is about a different car, the 2017 Mazda 3. However, it is still accessible from the selected car via links, so may be relevant.

DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	INSPECT POWER SUPPLY (SYSTEM) CIRCUIT Switch the ignition ON (engine off). Measure the voltage at the DSC HU/CM connector terminal Q (vehicle harness side) and body ground. Is the voltage B+?	Yes	Go to the next step.
		No	Refer to the wiring diagram and verify whether or not there is a common connector between IG1 relay and DSC HU/CM terminal Q (vehicle harness side). 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 8.
2	VERIFY OPEN OR SHORT CIRCUIT IN BRAKE SWITCH SIGNAL Switch the ignition ON (engine off). Measure the voltage between the PCM connector terminal 2G (vehicle harness-side) and body ground when the brake pedal is depressed and released. Voltage Brake pedal depressed: B+Brake pedal released: 1 V or less Is the voltage normal?	Yes	Go to the Step 8.
		No	If it is B+ under any condition, then go to the next step. If it is 1 V or less under any condition, then go to Step 4.
3	INSPECT BRAKE SWITCH SIGNAL FOR SHORT TO POWER SUPPLY CIRCUIT Disconnect the brake switch connector. Measure voltage between the brake switch connector terminal D (vehicle harness-side) and body ground. Is the voltage 1 V or less?	Yes	Go to Step 5.
		No	Refer to the wiring diagram and verify whether or not there is a common connector between PCM connector terminal 2G (vehicle harness-side) and brake switch connector terminal D (vehicle harness side). 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 8.
4	INSPECT BRAKE SWITCH SIGNAL FOR OPEN CIRCUIT Disconnect the PCM connectors. Disconnect the brake switch connector. Inspect continuity between the PCM and brake switch as follows. PCM connector terminal 2G (vehicle harness-side) and brake switch connector terminal D (vehicle 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 PCM connector terminal 2G (vehicle harness-side) and brake switch connector terminal D (vehicle harness side). 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 8.
5	INSPECT BRAKE SWITCH Inspect the brake switch. (See BRAKE SWITCH INSPECTION .) Is the brake switch normal?	Yes	Go to the next step.
		No	Replace the brake switch, then go to Step 8. (See BRAKE PEDAL REMOVAL/INSTALLATION .)
6	PERFORM REAR BODY CONTROL MODULE (RBCM) DTC INSPECTION Reconnect all disconnected connectors. Using the M-MDS, perform the DTC inspection for the rear body control module (RBCM). (See DTC INSPECTION [REAR BODY CONTROL MODULE (RBCM)] .) Are any DTCs detected?	Yes	Go to applicable DTC inspection. (See DTC TABLE [REAR BODY CONTROL MODULE (RBCM)] .)
		No	Go to the next step.
7	PERFORM PCM DTC INSPECTION Using the M-MDS, perform the DTC inspection for the PCM. (See ON-BOARD DIAGNOSTIC TEST [PCM (SKYACTIV-G 2.0, SKYACTIV-G 2.5)] .) Are any DTCs detected?	Yes	Go to applicable DTC inspection. (See DTC TABLE [PCM (SKYACTIV-G 2.0, SKYACTIV-G 2.5)] .)
		No	Go to the next step.
8	VERIFY THAT THE SAME DTC IS NOT PRESENT Reconnect all disconnected connectors. Clear the DTCs from the memory. (See ON-BOARD DIAGNOSIS [DYNAMIC STABILITY CONTROL (DSC)] .) Start the engine and drive the vehicle at 20 km/h {12 mph} or more. Are the same DTCs present?	Yes	Repeat the inspection from Step 1.
		No	Go to the next step.
9	VERIFY THAT NO OTHER DTCS ARE PRESENT 2 Are any other DTCs output?	Yes	Go to the applicable DTC inspection. (See ON-BOARD DIAGNOSIS [DYNAMIC STABILITY CONTROL (DSC)] .)
		No	DTC troubleshooting completed.