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Home >> Acura >> 2025 >> MDX Base >> Repair and Diagnosis >> Steering >> Steering Control Systems >> Body Electrical System - System Description - DTC Troubleshooting Index >> Tests >> Body Electrical Troubleshooting - B-CAN System Diagnosis Test Mode 1 and Test Mode 2 (without the HDS)

Body Electrical Troubleshooting - B-CAN System Diagnosis Test Mode 1 and Test Mode 2 (without the HDS)

Shift to Test Mode 1 

Check the PCM for DTCs and troubleshoot PCM or F-CAN loss of communication errors first, then do this diagnosis if the HDS is not available.

1. Check the No. A20  and the No. B29 

fuses. If a fuse is blown, find and correct the cause, then replace the fuse(s).

2. Turn the front individual map light switch OFF, the interior light switch to the DOOR position, and close all doors.

NOTE:

Do steps 3-7 within 10 seconds.

3. Turn the vehicle to the ON mode.

4. Pull and hold the passing switch in its PASSING position.

GHH659663Courtesy of HONDA, U.S.A., INC.

5. While holding the combination light switch in the PASSING position, turn to the PARKING position, then release, pull, and hold the combination light switch in its PASSING position.

6. Turn the combination light switch to OFF, then turn it to the PARKING position, and turn to the OFF position two more times.

7. Release the combination light switch.

8. Wait 5 seconds, and watch the front individual map lights. When the lights flash quickly once, the system enters in Test Mode 1.

9. If the individual map lights keeps blinking after entering Test Mode 1. Check for B-CAN unit communication error.

Error Display code(blinking pattern)
Communication bus line error (BUS OFF). 1
The body control module cannot receive signals from the gauge control module. 5

10. If there is a malfunction when the display code is checked, the code will be displayed. If there is no malfunction, nothing will be displayed. When the display code is displayed, it is displayed ON/OFF in 0.5 second intervals, repeating the display every 3 seconds. The codes are displayed repeatedly in ascending order starting from the smallest value code.

NOTE: If the test times out, turn the vehicle to the OFF (LOCK) mode, and repeat steps 3
GHH659664Courtesy of HONDA, U.S.A., INC.

The control unit that has stored the code can be identified by the number shown after the letter "PA" on the multi-information display (MID).

Control Unit Control Unit I.D. Number
Relay control module 11
Body control module 18
Driver's door control unit 30
Power tailgate control unit 31
Gauge control module 50
Climate control unit 51
Center display unit 57
Automatic lighting control unit-sensor 72
Master lighting control unit 7F
Telematics control unit 91
Driver's power seat control unit 95
Left side BSI radar unit 9F
Ventilated seat control unit A2
Front seat heater control unit A2
Front passenger's power seat control unit A3
Right side BSI radar unit A7
Second row seat heater control unit AC
Wireless charger AF
NOTE:

You can also check B-CAN communication status by the following methods:

Record all DTCs and sort them by DTC type, then troubleshoot them in this order:

12. Clear the DTCs by pressing and holding the right multi-function steering wheel controller for about 10 seconds.

13. You will hear a beep to confirm the codes have been cleared. Operate the devices that failed, and recheck for codes.

Shift to Test Mode 2 

NOTE:

Do steps 14-17 within 10 seconds.

14. Pull and hold the combination light switch in its PASSING position

GHH659665Courtesy of HONDA, U.S.A., INC.

15. While holding the combination light switch is in PASSING position, turn to the PARKING position, then release, pull, and hold the combination light switch in its PASSING position.

16. Turn the combination light switch to OFF, then turn to the PARKING position, and turn to OFF two more times.

17. Release the combination light switch.

18. Wait 5 seconds, and watch the individual map lights. When the lights flash two times quickly and then turn off, the system is in Test Mode 2.

NOTE:

If you repeat this procedure, the system automatically returns to Test Mode 1.

19. The following tables list the circuits that can be checked in Test Mode 2. Operate the switch that is most closely related to the problem. If the circuit is OK, the individual map lights blink once. If the circuit is faulty, there is no such indication.

Body Control Module 

Item
Driver's door switch Windshield wiper HI/LO switch
Front passenger's door switch Windshield wiper INT/LO switch
Left rear door switch Windshield wiper MIST switch
Right rear door switch Windshield wiper intermittent dwell time controller
Item
Full latch switch (power tailgate closer unit) Windshield washer switch
Tailgate outer handle switch Rear window wiper switch
Hazard warning switch Rear window wiper INT switch
Turn signal switch (LEFT) Rear window washer switch
Turn signal switch (RIGHT) Heated windshield wiper area switch
Headlight switch (ON) Hands free access power tailgate sensor
Headlight switch (OFF) Driver's door outer handle touch sensor (LOCK)
Lighting switch Front passenger's door outer handle touch sensor (LOCK)
Dimmer switch Driver's door outer handle touch sensor (UNLOCK)
Passing switch Front passenger's door outer handle touch sensor (UNLOCK)
Fog light switch Left rear door outer handle touch sensor (LOCK)
Electric parking brake switch Right rear door outer handle touch sensor (LOCK)
TCM (P position/mode) Left rear door outer handle touch sensor (UNLOCK)
Brake pedal position switch Right rear door outer handle touch sensor (UNLOCK)
Left one-touch access switch (seat-back side) Left rear door lock knob switch (UNLOCK)
Left one-touch access switch (seat-cushion side) Right rear door lock knob switch (UNLOCK)
Right one-touch access switch (seat-back side)  
Right one-touch access switch (seat-cushion side)  

Driver's Door Control Unit 

Item
Driver's door lock switch (UNLOCK) Power window master switch(Driver's window UP, DOWN, AUTO)
Driver's door lock switch (LOCK)
Driver's door lock knob switch (UNLOCK) Power window master switch(Front passenger's window UP, DOWN, AUTO)
Driver's door lock knob switch (LOCK)
Driver's door key cylinder switch (UNLOCK) *1 Power window master switch(Left rear window UP, DOWN, AUTO)
Driver's door key cylinder switch (LOCK) *1
Driving position memory switch (SET) Power window master switch(Right rear window UP, DOWN, AUTO)
Driving position memory switch (POSITION 1)
Driving position memory switch (POSITION 2) Power mirror switch (RETRACT)
Driving position memory switch (POSITION 3) Driver's power tailgate switch *2

*1: Be sure to rotate the door key cylinder switch two times to the desired test position (lock and lock). This ensures the door lock knob switch will no longer respond in that appropriate position, during door key cylinder switch test on third rotation.*2:'25

Gauge Control Module 

Item
Audio remote-HFL switch VSA OFF switch
Brake fluid level switch ACC combination switch
Automatic brake hold switch Idle stop OFF switch
Integrated dynamics system switch ( ) Head up display switch (HUD TILT )
Integrated dynamics system switch ( ) Head up display switch (HUD TILT )
Safety support switch Head up display switch (HUD ILLUMI+)
Dashlights brightness control switch Head up display switch (HUD ILLUMI-)
Washer fluid level switch  

Driver's Power Seat Control Unit 

Item
Driver's slide switch (Forward) Driver's tilt switch (UP)
Driver's slide switch (Backward) Driver's tilt switch (DOWN)
Driver's recline switch (Forward) Driver's height switch (UP)
Driver's recline switch (Backward) Driver's height switch (DOWN)

*1: With 12-way power seat*2: With 16-way power seat

Item
Driver's lumbar support adjustment switch ( ) *1 Driver's lumbar support adjustment switch ( ) *1
Driver's lumbar support adjustment switch ( ) *1 Driver's lumbar support adjustment switch ( ) *1
Driver's bolster/lumbar/thigh support adjustment switch ( ) *2 Driver's bolster/lumbar/thigh support adjustment switch ( ) *2
Driver's bolster/lumbar/thigh support adjustment switch ( ) *2 Driver's bolster/lumbar/thigh support adjustment switch ( ) *2
Driver's mode select switch (UP) *2 TCM (P position/mode)
Driver's mode select switch (DOWN) *2  

*1: With 12-way power seat*2: With 16-way power seat

Front Passenger's Power Seat Control Unit 

Item
Front passenger's slide switch (Forward) Front passenger's tilt switch (UP)
Front passenger's slide switch (Backward) Front passenger's tilt switch (DOWN)
Front passenger's recline switch (Forward) Front passenger's height switch (UP)
Front passenger's recline switch (Backward) Front passenger's height switch (DOWN)
Front passenger's lumbar support adjustment switch ( ) *1 Front passenger's lumbar support adjustment switch ( ) *1
Front passenger's lumbar support adjustment switch ( ) *1 Front passenger's lumbar support adjustment switch ( ) *1
Front passenger's bolster/lumbar/thigh support adjustment switch ( ) *2 Front passenger's bolster/lumbar/thigh support adjustment switch ( ) *2
Front passenger's bolster/lumbar/thigh support adjustment switch ( ) *2 Front passenger's bolster/lumbar/thigh support adjustment switch ( ) *2
Front passenger's mode select switch (UP) *2 Front passenger's mode select switch (DOWN) *2

*1: With 12-way power seat*2: With 16-way power seat

Relay Control Module 

Item
Hood latch switch