DTC B15D0: MOST Communication Malfunction: Procedure

1. Engine switch off.
2. Turn the engine switch on (ACC) and check if the audio system activates and if the speakers operate.

   HINT: 

   • Choose a source such as radio so that sound can be output from the speakers.
   • If sound from the speakers is low, turn up the volume.

   Result

   Model	Proceed to
   The audio system activates when the engine switch is turned on (ACC) but the sound stops being output when the amplifier output exceeds a certain level.	A
   Even after the engine switch is turned on (ACC), the audio system does not activate and sound is not output from the speakers.	B

   HINT: 

   • If a short occurs in a speaker circuit, the sound from the corresponding speaker will be low or almost impossible to hear. If the volume is turned up in this situation, to prevent excessive current flow due to the short circuit, the stereo component amplifier assembly stops operating when its output exceeds a certain level. When the operation of the stereo component amplifier assembly stops, the navigation system will not function normally. This is because MOST communication will stop due to the shut down of the amplifier causing an error in the MOST network. The stereo component amplifier assembly will start operating again when the engine switch is turned off and back on (ACC) again. However, the amplifier will stop operating again if its output exceeds a certain level.
   • When the stereo component amplifier assembly stops operating and a malfunction occurs in the navigation system due to a short in a speaker circuit, this DTC will be stored. In this case, check each speaker circuit and repair or replace malfunctioning parts, and then recheck for DTCs.

B → See step   2 

A → See step   17 

1. Display the "MOST Line Check" screen . Refer to DTC CHECK / CLEAR .
   Fig 1: Identifying MOST Line Check Display

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. Check the result on the "MOST Line Check" screen.

      Result

      Result	Proceed to
      "NCON" is displayed for "AMP".	A
      "NCON" is displayed for "AUDIO".	B
      "OK" is displayed for all items.	C

      HINT: 

      • When "NCON" is displayed for more than 1 item, proceed to the step for the device that has the smallest node position number.
      • The "MOST Line Check" screen can be displayed only when DTC B15D0 is stored.
      TEXT IN ILLUSTRATION
      
      

      *1	Node position number for devices that use MOST communication
      *2	Device Name
      *3	Result

C → See step   13 

B → See step   8 

A: Go to next step 

1. Check the MOST communication line connector.
   1. Check the MOST communication line connectors of the radio receiver assembly and stereo component amplifier assembly . Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE .
2. Display the "MOST Line Check" screen and check the result . Refer to DTC CHECK / CLEAR .

   Result

   Result	Proceed to
   "NCON" is displayed for "AMP".	A
   The screen cannot be changed to the "MOST Line Check" screen.	B

   HINT: 

   When the malfunction in the MOST network is repaired, the screen cannot be changed to the "MOST Line Check" screen.

B → END 

A: Go to next step 

1. Disconnect the P43 stereo component amplifier assembly connector.
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   P43-3 (WUI) - Body ground	Engine switch on (ACC)	4.5 V or higher

NG → See step   5 

OK → See step   7 

1. Disconnect the P43 stereo component amplifier assembly connector.
2. Disconnect the J106 radio receiver assembly connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   P43-3 (WUI) - J106-26 (WUO)	Always	Below 1 Ω
   P43-3 (WUI) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   6 

1. Check the MOST communication line connector.
   1. Check the MOST communication line connectors of the radio receiver assembly and display and navigation module display . Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE .
2. Display the "MOST Line Check" screen and check the result . Refer to DTC CHECK / CLEAR .

   Result

   Result	Proceed to
   "NCON" is displayed for "AUDIO".	A
   The screen cannot be changed to the "MOST Line Check" screen.	B

   HINT: 

   When the malfunction in the MOST network is repaired, the screen cannot be changed to the "MOST Line Check" screen.

B → END 

A: Go to next step 

1. Disconnect the J106 radio receiver assembly connector.
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   J106-12 (WUI) - Body ground	Engine switch on (ACC)	4.5 V or higher

NG → See step   10 

OK → See step   11 

1. Disconnect the J106 radio receiver assembly connector.
2. Disconnect the J101 display and navigation module display connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   J106-12 (WUI) - J101-8 (WUO)	Always	Below 1 Ω
   J106-12 (WUI) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   12 

1. Disconnect the J101 display and navigation module display connector.
2. Disconnect the J106 radio receiver assembly connector.
3. Disconnect the P43 stereo component amplifier assembly connector.
4. Measure the resistance between the display and navigation module display and the stereo component amplifier assembly according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   J101-1 (MI+) - P43-6 (MO+)	Always	Below 1 Ω
   J101-5 (MI-) - P43-12 (MO-)	Always	Below 1 Ω
   J101-2 (SLDI) - P43-11 (SLDO)	Always	Below 1 Ω
   J101-1 (MI+) - Body ground	Always	10 kΩ or higher
   J101-5 (MI-) - Body ground	Always	10 kΩ or higher
   J101-2 (SLDI) - Body ground	Always	10 kΩ or higher

5. Measure the resistance between the display and navigation module display and the radio receiver assembly according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   J101-3 (MO+) - J106-9 (MI+)	Always	Below 1 Ω
   J101-7 (MO-) - J106-23 (MI-)	Always	Below 1 Ω
   J101-6 (SLDO) - J106-10 (SLDI)	Always	Below 1 Ω
   J101-3 (MO+) - Body ground	Always	10 kΩ or higher
   J101-7 (MO-) - Body ground	Always	10 kΩ or higher
   J101-6 (SLDO) - Body ground	Always	10 kΩ or higher

6. Measure the resistance between the radio receiver assembly and stereo component amplifier assembly according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   J106-11 (MO+) - P43-4 (MI+)	Always	Below 1 Ω
   J106-25 (MO-) - P43-10 (MI-)	Always	Below 1 Ω
   J106-24 (SLDI) - P43-5 (SLDI)	Always	Below 1 Ω
   J106-11 (MO+) - Body ground	Always	10 kΩ or higher
   J106-25 (MO-) - Body ground	Always	10 kΩ or higher
   J106-24 (SLDI) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Clear the DTCs . Refer to DTC CHECK / CLEAR .
2. Recheck for DTCs and check if the same DTC is output again.

   OK

   No DTCs are output.

NG → See step   15 

OK → See step   16