DTC U0184; U0187; Communication Errors

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.

DETECTION CONDITION & POSSIBLE CAUSE

Description	U0184:00 Communication error with tuner and amp unit (TAU) U0187:00 Communication error with CD player
Detection condition	U0184:00 The connectivity master unit (CMU) cannot receive a CAN signal from the tuner and amp unit (TAU) for 5 s or more. U0187:00 The connectivity master unit (CMU) cannot receive a CAN signal from the CD player for 5 s or more.
Fail-safe function	U0184:00 Not applicable U0187:00 Not applicable
Possible cause	Connectivity master unit (CMU) connector or terminal malfunction Tuner and amp unit (TAU) connector or terminal malfunction CD player connector or terminal malfunction (With CD player) Short to power supply in wiring harness between the following terminals: Connectivity master unit (CMU) terminal 2I-Tuner and amp unit (TAU) terminal 2O Connectivity master unit (CMU) terminal 2I-CD player terminal G (With CD player) Short to ground in wiring harness between the following terminals: Connectivity master unit (CMU) terminal 2J-Tuner and amp unit (TAU) terminal 2Q Connectivity master unit (CMU) terminal 2J-CD player terminal H (With CD player) Short between circuits in the following wiring harness: Connectivity master unit (CMU) terminal 2I-Tuner and amp unit (TAU) terminal 2O Connectivity master unit (CMU) terminal 2J-Tuner and amp unit (TAU) terminal 2Q Connectivity master unit (CMU) terminal 2I-CD player terminal G (With CD player) Connectivity master unit (CMU) terminal 2J-CD player terminal H (With CD player) Tuner and amp unit (TAU) power supply circuit malfunction Connector C-36 connector or terminal malfunction Open circuit in wiring harness between the following terminals: Connectivity master unit (CMU) terminal 2I-Connector C-36 Connectivity master unit (CMU) terminal 2J-Connector C-36 Tuner and amp unit (TAU) terminal 2O-Connector C-36 Tuner and amp unit (TAU) terminal 2Q-Connector C-36 CD player terminal G-Connector C-36 (With CD player) CD player terminal H-Connector C-36 (With CD player) Open circuit in wiring harness between tuner and amp unit (TAU) terminal 2W and ground Open circuit in wiring harness between CD player terminal A and ground (With CD player) CD player power supply circuit malfunction (With CD player) Short to ground in wiring harness between MAIN 200 A fuse and CD player terminal Z MAIN 200 A fuse malfunction ROOM 15 A fuse malfunction Open circuit in wiring harness between battery positive terminal and CD player terminal Z Tuner and amp unit (TAU) malfunction CD player malfunction (With CD player) Connectivity master unit (CMU) malfunction

CAUTION:

When disconnecting the connector, verify that there is no looseness, damage, deformation, corrosion, or poor connection of the connector terminals.

DIAGNOSTIC PROCEDURE

Step	Inspection		Action
1	INSPECT FOR POWER SUPPLY-RELATED MALFUNCTION Switch the ignition ON (engine off). Perform the DTC inspection using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [PCM (SKYACTIV-G 2.0, SKYACTIV-G 2.5)] .) (See DTC INSPECTION [i-ELOOP] .) (See DTC INSPECTION [CONNECTIVITY MASTER UNIT] .) Is the power supply or DC-DC converter-related DTC displayed?	Yes	NOTE: It may be affected by power supply-related or DC-DC converter malfunction. Repair the malfunctioning location according to the applicable DTC troubleshooting.(See DTC TABLE [PCM (SKYACTIV-G 2.0, SKYACTIV-G 2.5)] .)(See DTC TABLE [i-ELOOP] .)(See DTC TABLE [CONNECTIVITY MASTER UNIT] .)
1		No	Go to the next step.
2	INSPECT FOR SHORT TO POWER SUPPLY IN CAN_H SIDE CIRCUIT OF PRIVATE-CAN Measure the voltage between connectivity master unit (CMU) terminal 2I (PRIVATE-CAN CAN_H side) and body ground. Is the voltage B+?	Yes	A short to power supply in CAN_H side circuit of PRIVATE-CAN has occurred. Go to Step 6.
2		No	Go to the next step.
3	INSPECT FOR SHORT TO GROUND IN CAN_L SIDE CIRCUIT OF PRIVATE-CAN Measure the voltage between connectivity master unit (CMU) terminal 2J (PRIVATE-CAN CAN_L side) and body ground. Is the voltage 0 V?	Yes	A short to ground in CAN_L side circuit of PRIVATE-CAN has occurred. Go to Step 7.
3		No	Go to the next step.
4	INSPECT BETWEEN PRIVATE-CAN_L AND PRIVATE-CAN_H SIDE CIRCUITS FOR SHORT BETWEEN CIRCUITS Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5] .) Measure the resistance between connectivity master unit (CMU) 2I and 2J terminals (vehicle wiring harness side). Is the resistance approx. 60 ohms?	Yes	Go to the next step. (PRIVATE-CAN is normal)
4		No	If the resistance is 0 ohm: A short between circuits has occurred in PRIVATE-CAN. Go to Step 8. If the resistance is 120 ohms: An open circuit in the PRIVATE-CAN has occurred. Go to Step 9.
5	DETERMINE MALFUNCTIONING LOCATION Reconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5] .) Clear the DTC for the connectivity master unit (CMU) using the M-MDS. (See CLEARING DTC [CONNECTIVITY MASTER UNIT] .) Switch the ignition ON (engine off or on) and wait for 12 s or more. Perform the DTC inspection for the connectivity master unit (CMU) using the M-MDS. (See DTC INSPECTION [CONNECTIVITY MASTER UNIT] .) Is there any of the following DTCs being displayed? U0184:00 U0187:00	Yes	If U0184:00 is only displayed: Go to Step 10. If U0187:00 is only displayed: Go to Step 11. If all DTCs are displayed: Replace the connectivity master unit (CMU), then go to Step 14. (See CONNECTIVITY MASTER UNIT (CMU) REMOVAL/INSTALLATION .)
5		No	Go to Step 15.
6	INSPECT WIRING HARNESS FOR SHORT TO POWER SUPPLY 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 following connectors: Connectivity master unit (CMU) Tuner and amp unit (TAU) CD player (With CD player) Reconnect 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 following terminals (vehicle wiring harness side). Connectivity master unit (CMU) terminal 2I Tuner and amp unit (TAU) terminal 2O CD player terminal G (With CD player) Is the voltage 0 V?	Yes	Go to Step 13.
6		No	Refer to the wiring diagram and verify if there is a common connector between the following terminals. Connectivity master unit (CMU) terminal 2I-Tuner and amp unit (TAU) terminal 2O Connectivity master unit (CMU) terminal 2I-CD player terminal G (With CD player) If there is a common connector: Inspect the common connector and terminals for corrosion, damage, or disconnection and the common wiring harnesses for short to power supply to determine the malfunctioning location. Repair or replace the malfunctioning location. If there is no common connector: Repair or replace the wiring harness which is shorted to the power supply. Go to Step 14.
7	INSPECT WIRING HARNESS FOR SHORT TO GROUND 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 following connectors: Connectivity master unit (CMU) Tuner and amp unit (TAU) CD player (With CD player) Inspect for continuity between the following terminals (vehicle wiring harness side) and body ground. Connectivity master unit (CMU) terminal 2J Tuner and amp unit (TAU) terminal 2Q CD player terminal H (With CD player) Is there continuity?	Yes	Refer to the wiring diagram and verify if there is a common connector between the following terminals. Connectivity master unit (CMU) terminal 2J-Tuner and amp unit (TAU) terminal 2Q Connectivity master unit (CMU) terminal 2J-CD player terminal H (With CD player) If there is a common connector: Inspect the common connector and terminals for corrosion, damage, or disconnection and the common wiring harnesses for short to ground to determine the malfunctioning location. Repair or replace the malfunctioning location. If there is no common connector: Repair or replace the wiring harness which is shorted to ground. Go to Step 14.
7		No	Go to Step 13.
8	INSPECT WIRING HARNESS FOR SHORT BETWEEN CIRCUITS 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 following connectors: Connectivity master unit (CMU) Tuner and amp unit (TAU) CD player (With CD player) Inspect between the following terminals (vehicle wiring harness side) for continuity. Connectivity master unit (CMU) terminals 2I and 2J Tuner and amp unit (TAU) terminals 2O and 2Q CD player terminals G and H (With CD player) Is there continuity?	Yes	Refer to the wiring diagram and verify if there is a common connector between the following terminals. Connectivity master unit (CMU) terminal 2I-Tuner and amp unit (TAU) terminal 2O Connectivity master unit (CMU) terminal 2J-Tuner and amp unit (TAU) terminal 2Q Connectivity master unit (CMU) terminal 2I-CD player terminal G (With CD player) Connectivity master unit (CMU) terminal 2J-CD player terminal H (With CD player) If there is a common connector: Inspect the common connector and terminals for corrosion, damage, or disconnection and the common wiring harnesses for short between circuits to determine the malfunctioning location. Repair or replace the malfunctioning location. If there is no common connector: Repair or replace the wiring harness which has shorted between circuits. Go to Step 14.
8		No	Go to Step 13.
9	INSPECT WIRING HARNESS FOR OPEN CIRCUIT 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 following connectors: Connectivity master unit (CMU) Tuner and amp unit (TAU) CD player (With CD player) Connector C-36 Inspect the wiring harness for continuity between the following terminals (vehicle wiring harness side). Connectivity master unit (CMU) terminal 2I-Connector C-36 Connectivity master unit (CMU) terminal 2J-Connector C-36 Tuner and amp unit (TAU) terminal 2O- Connector C-36 Tuner and amp unit (TAU) terminal 2Q- Connector C-36 CD player terminal G-Connector C-36 (With CD player) CD player terminal H-Connector C-36 (With CD player) Is there continuity?	Yes	Refer to the wiring diagram and verify if there is a common connector between the following terminals. Connectivity master unit (CMU) terminal 2I-Connector C-36 Connectivity master unit (CMU) terminal 2J-Connector C-36 Tuner and amp unit (TAU) terminal 2O-Connector C-36 Tuner and amp unit (TAU) terminal 2Q-Connector C-36 CD player terminal G-Connector C-36 (With CD player) CD player terminal H-Connector C-36 (With CD player) If there is a common connector: Inspect the common connector and terminals for corrosion, damage, or disconnection and the common wiring harnesses for an open circuit to determine the malfunctioning location. Repair or replace the malfunctioning location. If there is no common connector: Repair or replace the wiring harness which has an open circuit. Go to Step 14.
9		No	Go to Step 13.
10	INSPECT TUNER AND AMP UNIT (TAU) RELATED-WIRING HARNESS FOR OPEN CIRCUIT 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 tuner and amp unit (TAU) connector. Inspect the wiring harness for continuity between tuner and amp unit (TAU) terminal 2W and ground. Is there continuity?	Yes	Go to the next step.
10		No	Repair or replace the wiring harness which has an open circuit, then go to Step 14.
11	INSPECT CD PLAYER RELATED-WIRING HARNESS FOR OPEN CIRCUIT 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 CD player connector. Inspect the wiring harness for continuity between CD player terminal A (vehicle wiring harness side) and ground. Is there continuity?	Yes	Go to the next step.
11		No	Repair or replace the wiring harness which has an open circuit, then go to Step 14.
12	VERIFY CD PLAYER POWER SUPPLY VOLTAGE Verify that the CD player connector is disconnected. Reconnect 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 CD player terminal Z (vehicle wiring harness side). Is the voltage B+?	Yes	Replace the CD player, then go to Step 14. (See CD PLAYER REMOVAL .) (See CD PLAYER INSTALLATION .)
12		No	Inspect the MAIN 200 A fuse and ROOM 15 A fuse. If the fuse is blown: Refer to the wiring diagram and verify if there is a common connector between MAIN 200 A fuse and CD player terminal Z. If there is a common connector: Inspect the common connector and terminals for corrosion, damage, or disconnection and the common wiring harnesses for short to ground to determine the malfunctioning location. Repair or replace the malfunctioning location. If there is no common connector: Repair or replace the wiring harness which is shorted 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 if there is a common connector between battery positive terminal and CD player terminal Z. If there is a common connector: Inspect the common connector and terminals for corrosion, damage, or disconnection and the common wiring harnesses for an open circuit to determine the malfunctioning location. Repair or replace the malfunctioning location. If there is no common connector: Repair or replace the wiring harness which has an open circuit. Go to Step 14.
13	PERFORM DTC INSPECTION AND DETERMINE MALFUNCTIONING LOCATION Always reconnect all disconnected connectors. Reconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5] .) Clear the DTC for the connectivity master unit (CMU) using the M-MDS. (See CLEARING DTC [CONNECTIVITY MASTER UNIT] .) Switch the ignition ON (engine off or on) and wait for 12 s or more. Perform the DTC inspection for the connectivity master unit (CMU) using the M-MDS. (See DTC INSPECTION [CONNECTIVITY MASTER UNIT] .) Is there any of the following DTCs being displayed? U0184:00 U0187:00	Yes	If U0184:00 is only displayed: Replace the tuner and amp unit (TAU), then go to the next step. (See TUNER AND AMP UNIT (TAU) REMOVAL/INSTALLATION .) If U0187:00 is only displayed: Replace the CD player, then go to the next step. (See CD PLAYER REMOVAL .) (See CD PLAYER INSTALLATION .) If all DTCs are displayed: Replace the connectivity master unit (CMU), then go to the next step. (See CONNECTIVITY MASTER UNIT (CMU) REMOVAL/INSTALLATION .)
13		No	Go to the next step.
14	VERIFY THAT REPAIRS HAVE BEEN COMPLETED Always reconnect all disconnected connectors. Reconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5] .) Clear the DTC for the connectivity master unit (CMU) using the M-MDS. (See CLEARING DTC [CONNECTIVITY MASTER UNIT] .) Switch the ignition ON (engine off or on) and wait for 12 s or more. Perform the DTC inspection for the connectivity master unit (CMU) using the M-MDS. (See DTC INSPECTION [CONNECTIVITY MASTER UNIT] .) Is the same DTC displayed?	Yes	Repeat the inspection from Step 1. If the malfunction recurs, replace the connectivity master unit (CMU). (See CONNECTIVITY MASTER UNIT (CMU) REMOVAL/INSTALLATION .) Go to the next step.
14		No	Go to the next step.
15	VERIFY OTHER DTCs Are any other DTCs displayed?	Yes	Repair the malfunctioning location according to the applicable DTC troubleshooting. (See DTC TABLE [CONNECTIVITY MASTER UNIT] .)
15	VERIFY OTHER DTCs Are any other DTCs displayed?	No	DTC troubleshooting completed.