Audio-Navigation System DTC: 2721 (2016 2017 2018)

DTC 2721 : TCU Diag

NOTE:

Check the vehicle battery condition first .
This navigation DTC sets when the TCU icon is red in the System Links.
Check any official Honda service website for more service information about the navigation system.
Before you troubleshoot, make sure to follow the General Troubleshooting Information .
Check the connectors for poor connections or loose terminals.

Problem verification
-1. Clear the hard error codes .

-2. Press the engine start/stop button to select the OFF mode.

-3. Check for hard error codes .

Is DTC 2721 indicated?

YES

The failure is duplicated, go to step 2.

NO

Intermittent failure, the system is OK at this time.
DTC check
-1. Check for hard error codes .

Is DTC 2601 indicated?

YES

Go to DTC 2601 troubleshooting .

NO

Go to step 3.
HFL diagnosis check
-1. Go into the System Diagnostic Mode, and select the HFL in the Unit Check menu, and check GA-NET and USB status .

Are GA-NET OK and USB OK indicated?

YES

Replace the audio-navigation unit .

NO: GA-NET OK and USB NG are indicated

Go to step 4.

NO: GA-NET NG and USB OK are indicated

Go to step 5.

NO: GA-NET NG and USB NG are indicated

Go to step 6.

Open wire check (HFT USB lines)

-1. Press the engine start/stop button to select the OFF mode.

-2. Disconnect the following connectors.

Audio-navigation unit connector J (5P)

Telematics control unit connector B (5P)

-3. Check for continuity between test points 1 and 2.

Test condition	OFF mode
	Audio-navigation unit connector J (5P): disconnected
	Telematics control unit connector B (5P): disconnected

Test circuit	Test point 1:Audio-navigation unit connector J (5P)	Test point 2:Telematics control unit connector B (5P)
USB GND	No. 1	No. 4
USB VBUS	No. 2	No. 1
USB DATA+	No. 3	No. 3
USB DATA-	No. 4	No. 2

Courtesy of HONDA, U.S.A., INC.

Courtesy of HONDA, U.S.A., INC.

Is there continuity?

YES

Replace the telematics control unit .

There is an open in the wire(s) between the audio-navigation unit and the telematics control unit. Replace the affected shielded harness.

Open wire check (GA BUS+ line, GA BUS- line)

-1. Press the engine start/stop button to select the OFF mode.

-2. Disconnect the following connectors.

Telematics control unit connector A (36P)

Audio-navigation unit connector D (12P)

-3. Check for continuity between test points 1 and 2.

Test condition	OFF mode
	Telematics control unit connector A (36P): disconnected
	Audio-navigation unit connector D (12P): disconnected
Test circuit	GA BUS+
Test point 1	Audio-navigation unit connector D (12P) No. 7 (BLU)
Test point 2	Telematics control unit connector A (36P) No. 15 (BLU)

Test circuit	GA BUS-
Test point 1	Audio-navigation unit connector D (12P) No. 1 (PNK)
Test point 2	Telematics control unit connector A (36P) No. 14 (PNK)

Courtesy of HONDA, U.S.A., INC.

Is there continuity?

YES

Replace the telematics control unit .

There is an open in the wire(s) between the audio-navigation unit and the telematics control unit. Replace the affected shielded harness.

Open wire check (+B BACK UP line)

-1. Press the engine start/stop button to select the OFF mode.

-2. Disconnect the following connector.

Telematics control unit connector A (36P)

-3. Measure the voltage between test points 1 and 2.

Test condition	OFF mode
	Telematics control unit connector A (36P): disconnected
Test circuit	+B BACK UP
Test point 1	Telematics control unit connector A (36P) No. 36 (GRN)
Test point 2	Body ground

Courtesy of HONDA, U.S.A., INC.

Is there battery voltage?

YES

The +B BACK UP wire is OK. Go to step 7.

Repair an open in the wire between the No. A29 (10 A) fuse in the under-hood fuse/relay box and the telematics control unit.

Open wire check (ACC line)

-1. Press the engine start/stop button to select the ON mode.

-2. Measure the voltage between test points 1 and 2.

Test condition	ON mode
	Telematics control unit connector A (36P): disconnected
Test circuit	ACC
Test point 1	Telematics control unit connector A (36P) No. 35 (PUR)
Test point 2	Body ground

Courtesy of HONDA, U.S.A., INC.

Is there battery voltage?

YES

Repair an open in the wire between the No. B19 (7.5 A) fuse in the under-dash fuse/relay box and the telematics control unit.

The ACC wire is OK. Go to step 8.

Open wire check (GND line)

-1. Press the engine start/stop button to select the OFF mode.

-2. Reconnect telematics control unit connector A (36P).

-3. Press the engine start/stop button to select the ON mode.

-4. Measure the voltage between test points 1 and 2.

Test condition	ON mode
Test circuit	GND
Test point 1	Telematics control unit connector A (36P) No. 18 (BLK)
Test point 2	Body ground

Courtesy of HONDA, U.S.A., INC.

Is there less than 0.2 V?

YES

Replace the telematics control unit .

Repair an open or high resistance in the wire between the telematics control unit and body ground (G601).