How to Check MOST Bus Condition

If the MOST bus network is broken, it is not possible to diagnose on the System Diagnostic Mode. To check the MOST bus connection, do the ECL test using the multi-information display (MID) in the gauge control module. This test is performed using the diagnostic function of the MOST_ECL line. If the MOST ECL circuit is shorted, ECL diagnosis will fail and display all double dashes.

NOTE:

Check the vehicle 12 volt battery condition first - Refer to: 12 Volt Battery Test .
If the ECL test results NG, always retry the test 2 or 3 times. Do not judge it as a failure at once.

1. Close all doors and the tailgate.

2. Turn the vehicle to the ON mode.

3. Press the right selector wheel on the ACC combination switch to dismiss all warning or information messages displayed on the multi-information display (MID).

4. Hold down the left selector wheel on the audio remote-HFL switch and then press and hold the BACK button until the MOST bus diagnosis screen is displayed (for about 5 seconds).

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5. This diagnosis checks Pwr (power) and Sig (signal) status about each control unit on the MOST bus network.

Meter (Gauge control module)
Infotainment (Infotainment control unit)
Amplifier (Stereo amplifier)
Remote Tuner (Tuner unit)

NOTE: The multi-information display (MID) may update to latest information after 35 seconds as maximum delay.

Symbols

Symbol		Status
Courtesy of HONDA, U.S.A., INC.	GREEN (OK)	The power or MOST signal status is OK at this time.
Courtesy of HONDA, U.S.A., INC.	RED (NG)	The control unit lost the power or cannot receive MOST signal. If the control unit lost the power, both the PWR and SIG symbol indicates it.
-	(Dash)	The control unit is offline. The control unit is not equipped to the vehicle (not used).

Check for Pwr and Sig indication pattern.

Indication Pattern

Pwr	Sig	Solution
Courtesy of HONDA, U.S.A., INC.	Courtesy of HONDA, U.S.A., INC.	If all control units indicate this pattern, the power and MOST signal status are OK at this time.
Courtesy of HONDA, U.S.A., INC.	Courtesy of HONDA, U.S.A., INC.	Check for MOST TX+/MOST RX+ and MOST TX-/MOST RX- lines between the first RED symbol control unit and the last GREEN symbol control unit. If the wire is OK, substitute these items to a known-good one - Refer to: Audio and Visual System Component Location Index or Audio and Visual System Component Location Index (2022 2023) , and recheck: Last GREEN symbol control unit First RED symbol control unit
Courtesy of HONDA, U.S.A., INC.	Courtesy of HONDA, U.S.A., INC.	Check for ground circuit for the RED symbol control unit. If the wires are OK, the control unit internal power circuit may be faulty. Substitute a known-good control unit - Refer to: Audio and Visual System Component Location Index or Audio and Visual System Component Location Index (2022 2023) , and recheck.
-	-	The control unit is either offline or not equipped. NOTE: If all units indicate double dashes, the MOST_ECL line may be shorted. Check for power and ground circuits for the control unit. If the wires are OK, substitute a known-good control unit - Refer to: Audio and Visual System Component Location Index or Audio and Visual System Component Location Index (2022 2023) and recheck.

NOTE: The indicated components shown may be different on the model or specifications.

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6. To exit the ECL test, press the BACK button on the audio remote-HFL switch, or turn the vehicle to the OFF (LOCK) mode.