Keyless Access System Symptom Troubleshooting - Cannot select ON mode with keyless access and with the keyless remote touching the engine start/stop switch (2025)

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2025 Honda Odyssey, 2024 Honda Odyssey, 2023 Honda Odyssey, 2022 Honda Odyssey, and 2021 Honda Odyssey. However, it is still accessible from the selected car via links, so may be relevant.

Refer to: Keyless Access System Description , Keyless Access System Description - Components , Keyless Access System Description - System Diagram

Cannot select ON mode with keyless access and with the keyless remote touching the engine start/stop switch

Keyless access system check 1:
Do this procedure 10 times:
- Turn the vehicle to the ON mode.
Does the system change to ON mode?

YES

Intermittent failure, the system is OK at this time. Check for loose or poor connection.

NO

Go to step 2.
Keyless access system check 2
-1. Touch the engine start/stop switch with the keyless remote. The buttons on the keyless remote should be facing you.

-2. Turn the vehicle to the ON mode.

Does the system change to ON mode?

YES

Go to Keyless Access System Symptom Troubleshooting - Cannot select ON mode with keyless access, but can select ON mode with the keyless remote touching the engine start/stop switch .

NO

Go to step 3.
Keyless access system check 3
-1. Select KEYLESS ACCESS CONTROL UNIT from the ONE-PUSH START system select menu with the HDS, and enter SELF CHECK.

SELF CHECK

Does the system communicate with the HDS?

YES

Go to step 4.

NO

Go to step 10.
Keyless access system check 4
-1. Reboot the HDS.

-2. Select model on the HDS screen.

-3. When prompted by the HDS, select YES when asked if the vehicle has keyless access system, then press and hold the engine start/stop switch button for at least 2 minutes. This selects the forced ON mode.

Does the system change to forced ON mode?

YES

Go to step 5.

NO

Go to step 16.

PCU DTC check

-1. Check for PCU DTCs with the HDS.

DTC Description	DTC

Are any DTCs indicated?

YES

Troubleshoot the PCU DTCs.

Go to step 6.

Keyless access DTC check

-1. Check for keyless access control unit DTCs with the HDS.

DTC Description	DTC

Are any DTCs indicated?

YES

Troubleshoot the keyless access control unit DTCs.

Go to step 7.

Backup DTC check

-1. Check for backup control unit DTCs with the HDS.

DTC Description	DTC

Are any DTCs indicated?

YES

Troubleshoot the backup control unit DTCs.

Go to step 8.

Keyless access system check 5
-1. Do the keyless access remote check using the all keyless remotes KEYLESS ACCESS REMOTE REMOVAL, INSTALLATION, AND TEST .

Are the all keyless remotes OK?

YES

Go to step 9.

NO

Replace the keyless remote KEYLESS ACCESS REMOTE REMOVAL, INSTALLATION, AND TEST and recheck.
Keyless access system check 6
-1. Turn the vehicle to the OFF (LOCK) mode.

-2. Remove all the keyless remotes from inside the vehicle. Place the keyless remotes more than 1.5 m (4.9 ft) away from the vehicle.

-3. When prompted by the HDS, select YES when asked if the vehicle has keyless access system, then press and hold the engine start/stop switch button for at least 2 minutes. This selects the forced ON mode.

-4. Do the registration of the body control module according to the instructions on the HDS screen.

-5. Select REGISTRATION from the ONE-PUSH START system select menu with the HDS, then select REPLACE PCU/BACKUP CONTROL/KEYLESS ACCESS CONTROL UNIT.

-6. Take the keyless remote into the vehicle, and clear the PCU DTCs with the HDS.

Do this procedure 10 times:
- Turn the vehicle to the ON mode.
Does the system change to ON mode?

YES

Intermittent failure, the system is OK at this time. Check for loose or poor connection.

NO

Replace the body control moduleBODY CONTROL MODULE REMOVAL AND INSTALLATION .
Open wire check (L-line)
-1. Turn the vehicle to the OFF (LOCK) mode.

-2. Disconnect the following connector.

Body control module connector A (66P)

-3. Check for continuity between test points 1 and 2.

Test condition

Vehicle OFF (LOCK) modeBody control module connector A (66P): disconnected

Test point 1

Data link connector (16P) (female terminals) No. 15:

Test point 2

Body control module connector A (66P) No. 53 - Refer to: BODY CONTROL MODULE CONNECTOR FOR INPUTS AND OUTPUTS

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

Is there 1.0 Ohm or less?

YES

Go to step 11.

NO

Repair an open or high resistance in the wire.
Shorted wire check (L-line)
-1. Check for continuity between test points 1 and 2.

Test condition

Vehicle OFF (LOCK) modeBody control module connector A (66P): disconnected

Test point 1

Data link connector (16P) (female terminals) No. 15:

Test point 2

Body ground

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

Is there 1 MOhm or more?

YES

Go to step 12.

NO

Repair a short to ground in the wire.
Engine start/stop switch operation check
-1. Do the engine start/stop switch test ENGINE START/STOP SWITCH REMOVAL, INSTALLATION, AND TEST .

Is the engine start/stop switch OK?

YES

Go to step 13.

NO

Replace the engine start/stop switch ENGINE START/STOP SWITCH REMOVAL, INSTALLATION, AND TEST .
Open wire check (SS1(+), SS2(-) lines)
-1. Disconnect the following connectors.

Engine start/stop switch 10P connectorBody control module connector C (66P)

-2. Check for continuity between test points 1 and 2 respectively.

Test condition

Vehicle OFF (LOCK) modeEngine start/stop switch 10P connector: disconnectedBody control module connector C (66P): disconnected

Test point 1

Engine start/stop switch 10P connector (female terminals) No. 6:

Test point 2

Body control module connector C (66P) No. 65 - Refer to: BODY CONTROL MODULE CONNECTOR FOR INPUTS AND OUTPUTS

Test point 1

Engine start/stop switch 10P connector (female terminals) No. 10:

Test point 2

Body control module connector C (66P) No. 66 - Refer to: BODY CONTROL MODULE CONNECTOR FOR INPUTS AND OUTPUTS

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

Is there 1.0 Ohm or less?

YES

The SS1(+) and SS2(-) wires are OK. Go to step 14.

NO

Repair an open or high resistance in the wire.
Open wire check (+B SMART line)
-1. Measure the voltage between test points 1 and 2.

Test condition

Vehicle OFF (LOCK) modeEngine start/stop switch 10P connector: disconnectedBody control module connector C (66P): disconnected

Test point 1

Engine start/stop switch 10P connector (female terminals) No. 5:

Test point 2

Body ground

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

Is there battery voltage?

YES

The +B SMART wire is OK. Go to step 15.

NO

Repair an open or high resistance in the wire. If wire is OK, check the under-dash fuse/relay box No. C16 (10 A) fuse circuit.
Open wire check (GND line)
-1. Check for continuity between test points 1 and 2.

Test condition

Vehicle OFF (LOCK) modeEngine start/stop switch 10P connector: disconnectedBody control module connector C (66P): disconnected

Test point 1

Engine start/stop switch 10P connector (female terminals) No. 1:

Test point 2

Body ground

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

Is there 1.0 Ohm or less?

YES

The GND wire is OK. Go to step 17.

NO

Repair an open or high resistance in the ground wire or poor ground (G403).

PCU DTC check

-1. Check for PCU DTCs with the HDS.

DTC Description	DTC

Are any DTCs indicated?

YES

Troubleshoot the PCU DTCs.

Go to step 17.

Open wire check (+B BACK UP, +B SMART lines)
-1. Disconnect the following connector.

Body control module connector A (66P)

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

Test condition

Vehicle OFF (LOCK) modeEngine start/stop switch 10P connector: disconnectedBody control module connector A (66P): disconnectedBody control module connector C (66P): disconnected

Test point 1

Body control module connector A (66P) No. 18 - Refer to: BODY CONTROL MODULE CONNECTOR FOR INPUTS AND OUTPUTS

Test point 2

Body ground

Test point 1

Body control module connector A (66P) No. 1 - Refer to: BODY CONTROL MODULE CONNECTOR FOR INPUTS AND OUTPUTS

Test point 2

Body ground

Is there battery voltage?

YES

The +B BACK UP and +B SMART wires are OK. Go to step 18.

NO

Repair an open or high resistance in the wire.
Open wire check (GND line)
-1. Disconnect the following connector.

Body control module connector B (66P)

-2. Check for continuity between test points 1 and 2 individually.

Test condition

Vehicle OFF (LOCK) modeEngine start/stop switch 10P connector: disconnectedBody control module connector A (66P): disconnectedBody control module connector B (66P): disconnectedBody control module connector C (66P): disconnected

Test point 1

Body control module connector A (66P) No. 51 - Refer to: BODY CONTROL MODULE CONNECTOR FOR INPUTS AND OUTPUTS

Test point 2

Body ground

Test point 1

Body control module connector B (66P) No. 1 - Refer to: BODY CONTROL MODULE CONNECTOR FOR INPUTS AND OUTPUTS

Test point 2

Body ground

Test point 1

Body control module connector B (66P) No. 51 - Refer to: BODY CONTROL MODULE CONNECTOR FOR INPUTS AND OUTPUTS

Test point 2

Body ground

Is there 1.0 Ohm or less?

YES

Replace the body control module BODY CONTROL MODULE REMOVAL AND INSTALLATION .

NO

Repair an open or high resistance in the ground wire or poor ground (G401, G402).