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 U0186:08 (CONNECTIVITY MASTER UNIT - US) DIAGNOSTIC PROCEDURE - WITH BOSE®

Step	Inspection	Results	Action
1	VERIFY AUDIO AMPLIFIER OPERATION Output audio in the cabin using the audio amplifier. (Such as radio, navigation) Is audio output from the vehicle speakers?	Yes	Verify that the repairs have been completed.
1		No	Go to the next step.
2	VERIFY SUPPLY VOLTAGE TO AUDIO AMPLIFIER Measure the voltage at audio amplifier terminal 1A (vehicle wiring harness side). Is the voltage B+?	Yes	Inspect the audio amplifier ground circuit for open circuit. (Refer to the [CIRCUIT INSPECTION] in the appropriate service information) Circuit is normal Replace the audio amplifier and perform the repair completion verification. (Refer to the [AUDIO AMPLIFIER REMOVAL/INSTALLATION] in the appropriate service information) Circuit is not normal Repair or replace the malfunctioning location and perform the repair completion verification.
2		No	Go to the next step.
3	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.
3		No	Repair or replace the malfunctioning location and perform the repair completion verification.
4	INSPECT AUDIO AMPLIFIER POWER SUPPLY CIRCUIT FOR SHORT TO GROUND AND OPEN CIRCUIT Inspect the power supply circuit for a short to ground and open circuit. (Refer to the [CIRCUIT INSPECTION] in the appropriate service information) Is the circuit normal?	Yes	Go to the next step.
4		No	Repair or replace the malfunctioning location and perform the repair completion verification.
5	INSPECT AUDIO AMPLIFIER GROUND 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.
5		No	Repair or replace the malfunctioning location and perform the repair completion verification.
6	VERIFY MOST WAKE UP CIRCUIT VOLTAGE Measure the voltage at audio amplifier terminal 2K (vehicle wiring harness side). Is the voltage B+?	Yes	Go to Step 11.
6		No	Go to the next step.
7	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.
7		No	Repair or replace the malfunctioning location and perform the repair completion verification.
8	INSPECT MOST WAKE UP 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.
8		No	Repair or replace the malfunctioning location and perform the repair completion verification.
9	INSPECT MOST WAKE UP 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.
9		No	Repair or replace the malfunctioning location and perform the repair completion verification.
10	INSPECT MOST WAKE UP 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.
10		No	Repair or replace the malfunctioning location and perform the repair completion verification.
11	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.
11		No	Repair or replace the malfunctioning location and perform the repair completion verification.
12	INSPECT MOST 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.
12		No	Repair or replace the malfunctioning location and perform the repair completion verification.
13	INSPECT MOST 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.
13		No	Repair or replace the malfunctioning location and perform the repair completion verification.
14	INSPECT MOST 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.
14		No	Repair or replace the malfunctioning location and perform the repair completion verification.
15	INSPECT FOR CONTINUITY BETWEEN MOST COMMUNICATION CIRCUIT SHIELD WIRE AND GROUND Inspect the applicable circuit for continuity with the body ground. (Refer to the [CIRCUIT INSPECTION] in the appropriate service information) Is there continuity?	Yes	Go to the next step.
15		No	Repair or replace the malfunctioning location and perform the repair completion verification.
16	DETERMINE MALFUNCTIONING LOCATION Replace the audio amplifier. (Refer to the [AUDIO AMPLIFIER REMOVAL/INSTALLATION] in the appropriate service information) Output audio in the cabin using the audio amplifier. (Such as radio, navigation) Is audio output from the vehicle speakers?	Yes	Verify that the repairs have been completed.
16		No	Put back the audio amplifier that was removed, replace the connectivity master unit (CMU), and perform the repair completion verification. (Refer to the [AUDIO AMPLIFIER REMOVAL/INSTALLATION] in the appropriate service information) (Refer to the [CONNECTIVITY MASTER UNIT (CMU) REMOVAL/INSTALLATION] in the appropriate service information)
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 connectivity master unit (CMU), then go to the next step. (Refer to the [CONNECTIVITY MASTER UNIT (CMU) 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.