Diagnostic 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.

DTC U0186:00 (CONNECTIVITY MASTER UNIT) DIAGNOSTIC PROCEDURE

Step	Inspection	Results	Action
1	INSPECT BODY CONTROL MODULE (BCM) AND CONNECTIVITY MASTER UNIT (CMU) FOR MALFUNCTION Perform the DTC inspection for the body control module (BCM) and the connectivity master unit (CMU). (Refer to the [DTC INSPECTION] in the appropriate service information) Are any communication error-related DTCs other than this DTC displayed?	Yes	Repair the malfunctioning location according to the applicable DTC troubleshooting. (Refer to the [DTC TABLE [BODY CONTROL MODULE (BCM)]] in the appropriate service information) (See DTC TABLE [CONNECTIVITY MASTER UNIT (US)] .)
1		No	Go to the next step.
2	VERIFY SOUND DURING CRANKING NOTE: If a CAN signal can be normally received during cranking, the audio amplifier mutes the sound. Switch the ignition to ACC. Output audio in the cabin using the audio amplifier. (Such as radio, navigation) Crank the engine. Was the audio muted?	Yes	Go to the next step.
2		No	Go to Step 4.
3	INSPECT CONNECTIVITY MASTER UNIT (CMU) FOR MALFUNCTION DEPENDING ON REPEATABILITY Clear the DTC recorded in the memory. (Refer to the [CLEARING DTC] in the appropriate service information) Because the connectivity master unit (CMU) is in sleep mode, perform the following operation. Switch the ignition OFF. Remove all of the remote transmitters from the vehicle, lock all doors, and then wait for 10 min. Perform the DTC inspection for the connectivity master unit (CMU). (Refer to the [DTC INSPECTION] in the appropriate service information) Is the same Pending DTC present?	Yes	Refer to the controller area network (CAN) malfunction diagnosis flow to inspect for a CAN communication error. (Refer to the [CONTROLLER AREA NETWORK (CAN) MALFUNCTION DIAGNOSIS FLOW] in the appropriate service information) If the CAN communication is normal, replace the connectivity master unit (CMU) and perform the repair completion verification. (Refer to the [CONNECTIVITY MASTER UNIT (CMU) REMOVAL/INSTALLATION] in the appropriate service information)
3		No	Go to repair completion verification 2.
4	INSPECT AUDIO AMPLIFIER CONNECTOR FOR MALFUNCTION Inspect the applicable connector and terminal. (Refer to the [CONNECTOR INSPECTION] in the appropriate service information) Are the connector and terminal normal?	Yes	Go to the next step.
4		No	Repair or replace the malfunctioning location and perform the repair completion verification.
5	INSPECT CONNECTIVITY MASTER UNIT (CMU) CONNECTOR FOR MALFUNCTION Inspect the applicable connector and terminal. (Refer to the [CONNECTOR INSPECTION] in the appropriate service information) Are the connector and terminal normal?	Yes	Go to the next step.
5		No	Repair or replace the malfunctioning location and perform the repair completion verification.
6	INSPECT AUDIO AMPLIFIER CAN COMMUNICATION CIRCUIT FOR SHORT TO GROUND Inspect the applicable circuit for a short to ground. (Refer to the [CIRCUIT INSPECTION] in the appropriate service information) Is the circuit normal?	Yes	Go to the next step.
6		No	Repair or replace the malfunctioning location and perform the repair completion verification.
7	INSPECT AUDIO AMPLIFIER CAN COMMUNICATION CIRCUIT FOR SHORT TO POWER SUPPLY Inspect the applicable circuit for a short to power supply. (Refer to the [CIRCUIT INSPECTION] in the appropriate service information) Is the circuit normal?	Yes	Go to the next step.
7		No	Repair or replace the malfunctioning location and perform the repair completion verification.
8	INSPECT AUDIO AMPLIFIER CAN COMMUNICATION CIRCUIT FOR OPEN CIRCUIT Inspect the applicable circuit for an open circuit. (Refer to the [CIRCUIT INSPECTION] in the appropriate service information) Is the circuit normal?	Yes	Go to the next step.
8		No	Repair or replace the malfunctioning location and perform the repair completion verification.
9	INSPECT AUDIO AMPLIFIER CAN COMMUNICATION CIRCUITS FOR SHORT CIRCUIT Inspect the applicable circuits for a short circuit. (Refer to the [CIRCUIT INSPECTION] in the appropriate service information) Is the circuit normal?	Yes	Go to the next step.
9		No	Repair or replace the malfunctioning location and perform the repair completion verification.
Repair completion verification 1	VERIFY THAT VEHICLE IS REPAIRED Install/connect the part removed/disconnected during the troubleshooting procedure. Clear the DTC recorded in the memory. (Refer to the [CLEARING DTC] in the appropriate service information) Perform the DTC inspection for the connectivity master unit (CMU). (Refer to the [DTC INSPECTION] in the appropriate service information) Is the same Pending DTC present?	Yes	Refer to the controller area network (CAN) malfunction diagnosis flow to inspect for a CAN communication error. (Refer to the [CONTROLLER AREA NETWORK (CAN) MALFUNCTION DIAGNOSIS FLOW] in the appropriate service information) If the CAN communication is normal, perform the diagnosis from Step 1. If the malfunction recurs, replace the audio amplifier, then go to the next step. (Refer to the [AUDIO AMPLIFIER REMOVAL/INSTALLATION] in the appropriate service information)
Repair completion verification 1		No	Go to the next step.
Repair completion verification 2	VERIFY IF OTHER DTCs ARE DISPLAYED Perform the DTC inspection. (Refer to the [DTC INSPECTION] in the appropriate service information) Are other DTCs displayed?	Yes	Repair the malfunctioning location according to the applicable DTC troubleshooting.
Repair completion verification 2		No	DTC troubleshooting completed.