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	VERIFY ALL SYSTEM DTCs Switch the ignition off. Switch the ignition ON (engine off or on) and wait for 10 s or more. Perform a CMDTC self-test using the MMDS. (See DTC INSPECTION [ELECTRIC PARKING BRAKE] .) Are any DTCs other than DTC U300A:29 displayed?	Yes	Repair or replace the malfunctioning part according to the applicable DTC troubleshooting. (See DTC TABLE [ELECTRIC PARKING BRAKE] .)
1		No	Go to the next step.
2	INSPECT ELECTRIC PARKING BRAKE CONTROL MODULE CONNECTOR CONDITION Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5] .) Disconnect the electric parking brake 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.
2		No	Repair or replace the connector, then go to Step 4.
3	VERIFY ELECTRIC PARKING BRAKE CONTROL MODULE POWER SUPPLY (IG1) VOLTAGE Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5] .) Switch the ignition ON (engine off or on). Measure the voltage at the electric parking brake control module terminal R (wiring harness-side). Is the voltage B+?	Yes	Go to the next step.
3		No	Inspect the C/U IG1 15 A fuse. If the fuse is blown: Refer to the wiring diagram and verify whether or not there is a common connector between IG1 relay terminal C and electric parking brake control module terminal R. 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. Replace the fuse. If the fuse is damaged: Replace the fuse. If the fuse is normal: Refer to the wiring diagram and verify whether or not there is a common connector between IG1 relay terminal C and electric parking brake control module terminal R. 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 the next step.
4	VERIFY THAT REPAIRS HAVE BEEN COMPLETED Always reconnect all disconnected connectors. Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5] .) Clear the DTC for the electric parking brake control module using the M-MDS. (See CLEARING DTC [ELECTRIC PARKING BRAKE] .) Perform the following procedure 3 times or more. Pull up the electric parking brake switch to operate the electric parking brake. Press down the electric parking brake switch to release the electric parking brake. Retrieve the electric parking brake control module DTCs using the M-MDS. (See DTC INSPECTION [ELECTRIC PARKING BRAKE] .) Is the same DTC displayed?	Yes	Repeat the inspection from Step 1. If the malfunction recurs, replace the electric parking brake control module. (See ELECTRIC PARKING BRAKE CONTROL MODULE REMOVAL/INSTALLATION .) Go to the next step.
4		No	Go to the next step.
5	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 [ELECTRIC PARKING BRAKE] .)
5		No	DTC troubleshooting completed.