DTC 2721 (2019 2020)

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.

1. Problem verification

   -1. Clear the hard error codes .

   -2. Turn the vehicle to the OFF (LOCK) mode.

   -3. Wait for at least 2 minutes.

   -4. 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.

2. DTC check

   -1. Check for hard error codes .

   Is DTC 2601 indicated?

   YES 

   Go to DTC 2601 troubleshooting .

   NO 

   Go to step 3.

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.

4. Open wire check (HFT USB lines)

   -1. Turn the vehicle to the OFF (LOCK) 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	Vehicle OFF (LOCK) 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 .

   NO 

   There is an open in the wire (s). Replace the affected shielded harness.

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

   -1. Turn the vehicle to the OFF (LOCK) 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	Vehicle OFF (LOCK) 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 (PNK)
   Test point 2	Telematics control unit connector A (36P) No. 15 (PNK)

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

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

   Is there continuity?

   YES 

   Replace the telematics control unit .

   NO 

   There is an open in the wire (s). Replace the affected shielded harness.

6. Open wire check (+B BACK UP AUDIO line)

   -1. Turn the vehicle to the OFF (LOCK) mode.

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

   Test condition	Vehicle OFF (LOCK) mode
   Test circuit	+B BACK UP AUDIO
   Test point 1	Telematics control unit connector A (36P) No. 36 (PUR)
   Test point 2	Body ground

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

   Is there battery voltage?

   YES 

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

   NO 

   Repair an open in the wire.

7. Open wire check (ACC/ACC RLY CL+/AUDIO DIODE- line)

   -1. Turn the vehicle to the ON mode.

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

   Test condition	Vehicle ON mode
   Test circuit	ACC/ACC RLY CL+/AUDIO DIODE-
   Test point 1	Telematics control unit connector A (36P) No. 35 (YEL)
   Test point 2	Body ground

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

   Is there battery voltage?

   YES 

   Repair an open in the wire.

   NO 

   The ACC/ACC RLY CL+/AUDIO DIODE- wire is OK. Go to step 8.

8. Open wire check (IG1 METER line)

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

   Test condition	Vehicle ON mode
   Test circuit	IG1 METER
   Test point 1	Telematics control unit connector A (36P) No. 30 (TAN)
   Test point 2	Body ground

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

   Is there battery voltage?

   YES 

   The IG1 METER wire is OK. Go to step 9.

   NO 

   Repair an open in the wire.

9. Open wire check (GND line)

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

   Test condition	Vehicle 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 .

   NO 

   Repair an open or high resistance in the wire or poor ground (G601).