Determination Procedure

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.

CAUTION:

When disconnecting the connector, verify that there is no looseness, damage, deformation, corrosion, or poor connection of the connector terminals.
When inspecting the connector, touch it with a paper clip or similar thin pin without directly inserting a tester probe into the terminal.
Disconnect the negative battery cable before performing any work that requires handling of connectors.

DETERMINING SHORT TO POWER SUPPLY LOCATION (CAN-BUS No. 7, US) - DIAGNOSTIC PROCEDURE

Step	Inspection		Action
1	INSPECT CAN LINE BETWEEN CONNECTOR C-49 AND BODY CONTROL MODULE (BCM) FOR SHORT TO POWER SUPPLY Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Disconnect the connector C-49. Connect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Switch the ignition ON (engine off). Measure the voltage at body control module (BCM) terminals 4R and 4Q. Is the voltage between 1.5-3.5 V?	Yes	Go to Step 3.
1		No	Go to the next step.
2	INSPECT BODY CONTROL MODULE (BCM) FOR SHORT TO POWER SUPPLY Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Disconnect the connector 4 which has body control module (BCM) terminals 4R and 4Q. Connect the connector C-49. Connect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Switch the ignition ON (engine off). Measure the voltage at body control module (BCM) terminals 4R and 4Q (wiring harness side). Is the voltage between 1.5-3.5 V?	Yes	Replace the body control module (BCM) because there is a short to the power supply in the body control module (BCM). (See BODY CONTROL MODULE (BCM) REMOVAL/INSTALLATION (US) .)
2		No	Repair or replace the wiring harness between the body control module (BCM) and connector C-49 because the wiring harness is shorted to the power supply.
3	INSPECT JB No. 2 FOR SHORT TO POWER SUPPLY Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Connect the connector C-49. Disconnect the connector C-48. Connect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Switch the ignition ON (engine off). Measure the voltage at body control module (BCM) terminals 4R and 4Q. Is the voltage between 1.5-3.5 V?	Yes	Go to the next step.
3		No	Replace the JB No. 2 because there is a short to the power supply in the JB No. 2.
4	INSPECT CAN LINE BETWEEN AUDIO AMPLIFIER AND CONNECTOR C-48 FOR SHORT TO POWER SUPPLY Measure the voltage at audio amplifier terminals 2N and 2M. (With Bose ® type audio) Measure the voltage at audio amplifier terminals 1Q and 1S. (Without Bose ® type audio) Is the voltage between 1.5-3.5 V?	Yes	Go to Step 6.
4		No	Go to the next step.
5	INSPECT AUDIO AMPLIFIER FOR SHORT TO POWER SUPPLY Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Disconnect the audio amplifier connector. Connect the connector C-48. Connect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Switch the ignition ON (engine off). Measure the voltage at body control module (BCM) terminals 4R and 4Q. Is the voltage between 1.5-3.5 V?	Yes	Replace the audio amplifier because there is a short to the power supply in the audio amplifier. (See AUDIO AMPLIFIER REMOVAL/INSTALLATION (US) .)
5		No	Repair or replace the wiring harness between the audio amplifier and connector C-48 because the wiring harness is shorted to the power supply.
6	INSPECT CAN LINE BETWEEN CONNECTOR C-48 AND CONNECTOR C-13 FOR SHORT TO POWER SUPPLY Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Connect the connector C-48. Disconnect the connector C-13. Connect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Switch the ignition ON (engine off). Measure the voltage at body control module (BCM) terminals 4R and 4Q. Is the voltage between 1.5-3.5 V?	Yes	Go to the next step.
6		No	Repair or replace the wiring harness between the connector C-48 and connector C-13 because the wiring harness is shorted to the power supply.
7	INSPECT CONNECTIVITY MASTER UNIT (CMU) FOR SHORT TO POWER SUPPLY Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US)) Disconnect the connectivity master unit (CMU) connector. Connect the connector C-13. Connect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US)) Switch the ignition ON (engine off). Measure the voltage at body control module (BCM) terminals 4R and 4Q. Is the voltage between 1.5-3.5 V?	Yes	Replace the connectivity master unit (CMU) because there is a short to the power supply in the connectivity master unit (CMU). (See CONNECTIVITY MASTER UNIT (CMU) REMOVAL/INSTALLATION .)
7		No	Repair or replace the wiring harness between the connectivity master unit (CMU) and connector C-13 because the wiring harness is shorted to the power supply.