DTC C0040-23: Brake Switch (No. 1 Signal) Circuit Malfunction (BCM): Outline

WARNING: This page is about a different car, the 2020 Mazda CX-30. However, it is still accessible from the selected car via links, so may be relevant.

DTC C0040:23 (BCM) DETECTION CONDITION AND POSSIBLE CAUSE

System malfunction location	Brake switch (No. 1 signal) circuit malfunction
Detection condition	The body control module (BCM) detects that the brake switch No. 1 signal is in the off condition for a continuous 5 times even though brake switch No. 2 signal changes.
Fail-safe	Determined by brake switch (No. 2 signal) with the brake pedal depressed.
Possible cause	CAUTION: Inspect the brake switch with it installed to the brake pedal, otherwise the brake switch may not operate normally. If the brake switch is removed from the brake pedal, replace the brake switch with a new one. Brake switch (No. 1 signal) connector or terminal malfunction Brake switch (No. 1 signal) malfunction Short to ground or open circuit in brake switch (No. 1 signal) power supply circuit Body control module (BCM) connector or terminal malfunction Short to ground in brake switch (No. 1 signal) signal circuit Open circuit in brake switch (No. 1 signal) signal circuit Body control module (BCM) malfunction
Courtesy of MAZDA MOTORS CORP.