Nissan Sentra B18 (2020-2025) Service Manual: Diagnosis System (av Control Unit)

Description

Description

The AV control unit on board diagnosis performs the functions listed in the table below:

Mode		Description
Self Diagnosis		Audio system diagnosis. Diagnoses the connections across system components.
Confirmation/Adjustment	Display Diagnosis	The following check functions are available: Color Spectrum Bar Gradation Bar Touch Panel Status Check
	Nissan Sentra Vehicle Signals	Diagnosis of signals can be performed for Nissan Sentra vehicle speed, lights, reverse, ignition, EQ pin, camera type and DC offset.
	Speaker Test	Individual speakers can be checked.
	Error History	Displays error name and error count.
	Camera System	The following functions are available: Adjust Guide Lines Confirm Guide Lines
	AV COMM Diagnosis	AV communication information is displayed.
	Delete Unit Connection Log	Erase the connection history of unit.
	Version Information	Version information of the AV control unit is displayed.
	Initialize Setting	System memory can be erased.

Perform CONSULT diagnosis if the AV control unit on board diagnosis does not start, or the screen does not display anything.

On Board Diagnosis Function

On Board Diagnosis Function

METHOD OF STARTING

AV Control Unit Self Diagnosis

1. Ignition switch ON.

2. Audio system OFF.

3. While pressing the MENU button, turn the VOL dial clockwise or counterclockwise for 40 clicks or more. Shifting from current screen to previous screen is performed by pressing BACK button.

   

4. The trouble diagnosis initial screen is displayed, and “Self Diagnosis” and “Confirmation/Adjustment” can be selected.

   

SELF-DIAGNOSIS MODE

1. Start the self-diagnosis function and select “Self Diagnosis”.

   • Self-diagnosis subdivision screen is displayed, and the self-diagnosis mode starts.

   • The bar graph visible on the center of the self-diagnosis subdivision screen indicates progress of the trouble diagnosis.

2. Diagnosis results are displayed after the self-diagnosis is completed. The unit names and the connection lines are color-coded according to the diagnostic results.

   Diagnosis results	Unit	Connection line
   Normal	Green	Green
   Connection malfunction	Gray	Yellow
   Unit malfunction Note	Red	Green

   Note:

   Control Unit (AV control unit) is displayed in red.

   • Replace AV control unit if “Self-Diagnosis did not run because of a control unit malfunction” is indicated. The symptom is AV control unit internal error. Refer to Removal and Installation.

   • If multiple errors occur at the same time for a single unit, the screen switch colors are determined according to the following order of priority: red > gray.

Detection Range of Self-diagnosis Mode

• The self-diagnosis mode allows the technician to diagnose the connection in the communication line between AV control unit and each unit and the internal operation of the AV control unit.

• Because the start condition of diagnosis function is a switch operation, the on board diagnosis function cannot be started up if any malfunction is detected in the AV control unit switches.

SELF-DIAGNOSIS RESULTS

Only Unit Part Is Displayed In Red

Screen switch	Description	Possible malfunction location / Action to take
Head Unit	Malfunction is detected in AV control unit power supply and ground circuits.	Check AV control unit power supply and ground circuits. Refer to Diagnosis Procedure. When no malfunction is detected in those circuits, replace AV control unit. Refer to Removal and Installation.
Meter	Malfunction is detected in combination meter power supply and ground circuits.	Check combination meter power supply and ground circuits. Refer to Diagnosis Procedure. When no malfunction is detected in those circuits, replace combination meter. Refer to Removal and Installation.

A Connecting Cable Between Units Is Displayed In Yellow

Area with yellow connection lines	Description	Possible malfunction location / Action to take
Head unit ⇔ Meter	Combination meter AV communication connection malfunction detected.	AV communication circuits between AV control unit and combination meter.

CONFIRMATION/ADJUSTMENT MODE

1. Start the diagnosis function and select “Confirmation/Adjustment”. The confirmation/adjustment mode indicates where each item can be checked or adjusted.

2. Select each switch on the “Confirmation/Adjustment Mode” screen to display the relevant trouble diagnosis screen. Touch the “Back” to return to the initial Confirmation/Adjustment Mode screen.

   

Display Diagnosis

Confirmation of the AV control unit screen operation.

Nissan Sentra Vehicle Signals

A comparison check can be made of each actual vehicle signal and the signals recognized by the system.

Speaker Test

Test tones can be generated to each speaker.

Error History

The self diagnosis results are judged depending on whether any error occurs from when Self Diagnosis is selected until the self diagnosis results are displayed.

However, the diagnosis results are judged normal if an error has occurred before the ignition switch is turned ON and then no error has occurred until the self diagnosis start. Check the Error Record to detect any error that may have occurred before the self diagnosis start because of this situation.

The frequency of occurrence is displayed in a count up manner. The actual count up method differs depending on the error item.

Count up method A

• The counter is set to 40 if an error occurs. 1 is subtracted from the counter if the condition is normal at a next ignition ON cycle.

• The counter lower limit is 1. The counter can be reset (no error record display) with the Delete log switch.

Count up method B

• The counter increases by 1 if an error occurs when ignition switch is ON. The counter will not decrease even if the condition is normal at the next ignition ON cycle.

• The counter upper limit is 50. Any counts exceeding 50 are ignored. The counter can be reset (no error record display) with the Delete log switch.

Display type of occurrence frequency	Error history display item
Count up method A	AV communication line, control unit (AV)
Count up method B	Other than the above

Error item

Some error items may be displayed simultaneously according to the cause. If some error items are displayed simultaneously, the detection of the cause can be performed by the combination of display items

Error item	Description	Possible cause
CONTROL UNIT (AV)	AV communication circuit initial diagnosis malfunction is detected.	Replace the AV control unit if the malfunction occurs constantly. Refer to Removal and Installation

Camera System

This mode is used to adjust the guide line display position of the rear view camera.

AV COMM Diagnosis

• The error counter displays “OK” if any malfunction was not detected in the past and displays “0” if a malfunction is detected. It increases by 1 if the condition is normal at the next ignition switch ON cycle. The upper limit of the counter is 39.

• The error counter is erased if “Reset” is pressed.

Items	Status (Current)	Counter (Past)
BUS OFF	OK / ???	OK / 0 ­ 39

Note:

"???" indicates UNKWN.

Delete Unit Connection Log

Deletes any unit connection records and error records from the AV control unit memory.

Version Information

Displays audio system version numbers.

Initialize Settings

Deletes data stored from the AV control unit.

Consult Function

CONSULT Function

CONSULT FUNCTIONS

CONSULT performs the following functions via communication with the AV control unit:

Diagnosis Mode	CGW Status			Description
	Restricted Mode	Diag Test Mode	Open Mode
ECU Identification	Display	Display	Display	The AV control unit part number is displayed.
Self Diagnostic Result	Display	Display	Display	The AV control unit self diagnostic results are displayed.
CGW Information	Display	Display	Display	Display the current CGW mode Enables CGW to switch mode
Data Monitor	Display	Display	Display	The AV control unit input/output data is displayed in real time.
Work Support	Non-display	Non-display	Display	Save or write VIN information.
Configuration	Display	Display	Display	The Nissan Sentra vehicle specification can be read and saved. The vehicle specification can be written when replacing AV control unit.
CAN Diag Support Monitor*	Display	Display	Display	Note: The mode is indicated, but not monitored.
Network-DTC*	Display	Display	Display	Display network DTC which AV control unit memorizes when performing "Diagnosis (All System)".

*: Displays when performing "Diagnosis (All System)".

ECU IDENTIFICATION

The part number of AV control unit is displayed.

SELF DIAGNOSTIC RESULT

Refer to DTC Index.

CGW INFORMATION

Displays the diagnosis mode which a user can perform in Diag Test mode/Open Mode by switching the CGW status from Restricted mode to Diag Test Mode/Open Mode.

For the method of switching CAN Gateway status, refer to CONSULT Function.

DATA MONITOR

Note:

The following table includes information (items) inapplicable to this Nissan Sentra vehicle. For information (items) applicable to this vehicle, refer to CONSULT display items.

Monitor Item [Unit]	Description
Sunload sensor [On/Off]	Indicates sunload sensor signal received from A/C auto amp. on CAN communication line.
Parking brake [On/Off]	Indicates condition of parking brake signal for the AV control unit.
IGN SIG [On/Off]	Indicates condition of ignition signal.
Auto ACC [On/Off]	Indicates condition of auto ACC signal.
ACC [On/Off]	Indicates condition of ACC signal.
Aux IN 1 [Con/No con]	Indicates connection condition of Aux in jack.
Aux IN 2 [Con/No con]	Indicates connection condition of USB.
REV SIG [On/Off]	Indicates condition of reverse signal received from transmission range switch.
ILLUM SIG [On/Off]	Indicates condition of illumination signal for the AV control unit.
Illumination Control[On/Off]	Indicates condition of illumination control signal for the AV control unit.

WORK SUPPORT

Test item	Description
SAVE VIN DATA	Allows the reading of VIN data written in AV control unit to store the specification in CONSULT.
WRITE VIN (SAVED DATA)	Allows the writing of the VIN data stored in CONSULT into the AV control unit.
WRITE VIN (MANUAL INPUT)	Allows the writing of the VIN data into the AV control unit by hand.

CONFIGURATION

Configuration has three functions as follows.

Function		Description
Read/Write Configuration	Before Replace ECU	Allows the reading of Nissan Sentra vehicle specification written in AV control unit to store the specification in CONSULT.
	After Replace ECU	Allows the writing of the Nissan Sentra vehicle information stored in CONSULT into the AV control unit.
Manual Configuration		Allows the writing of the Nissan Sentra vehicle specification into the AV control unit by hand.