What this code means
B1664 may indicate a problem in the rear interior LF antenna circuit used by the keyless access control system.
What the vehicle may do
- The keyless access system may behave intermittently.
- Push-button start authorization may not work as expected.
- The system may store the code even if the condition is not present during testing.
Possible fault areas
- Rear interior LF antenna
- EXT R+ and EXT R- circuit wiring
- Loose or poor connector connections
- Keyless access control unit
Diagnostic path
Code meaning and diagnostic direction
On this Accord, B1664 is handled through the keyless access control unit. In plain language, this code may point to a problem in the rear interior LF antenna circuit used by the keyless access system. The driver may notice keyless access or push-button start behavior that is intermittent or not working as expected. The possible fault areas can include the rear interior LF antenna, the EXT R+ and EXT R- circuit wiring, connector condition, or the keyless access control unit itself. The goal here is not to guess at the antenna or the control unit. We are going to confirm the code first, then check whether the control unit can drive the rear cabin antenna circuit, and finally check the wiring if that output is missing.
Confirm B1664 before testing
Start by clearing the DTCs with the HDS. From the HDS, select the MODE MENU, enter the SELF CHECK, run the SELF CHECK, and then check for DTCs again. If B1664 is indicated, continue to the rear interior LF antenna circuit output check. If B1664 is not indicated, treat it as an intermittent failure for now. The system is okay at this time, so check closely for loose or poor connections before going any deeper.
Check the rear interior LF antenna output
Next, check the keyless access control unit output on the EXT R+ and EXT R- lines. Press the engine start/stop button to select the OFF mode, then disconnect the rear interior LF antenna 2P connector. Press the engine start/stop button again to select the ON mode. On the HDS, select KEYLESS ACCESS CONTROL from the ONE-PUSH START system select menu, enter FUNCTIONAL TESTS, and connect the voltmeter at the rear interior LF antenna connector. Test point 1 is rear interior LF antenna 2P connector No. 1, the LT GRN wire. Test point 2 is rear interior LF antenna 2P connector No. 2, the WHT wire. Then select CABIN REAR ANTENNA with the HDS. If there is voltage, replace the rear interior LF antenna. If there is no voltage, keep going and check the wiring between the antenna connector and the keyless access control unit.
Check for an open or high resistance in the antenna lines
For the open wire check, press the engine start/stop button to select the OFF mode. Disconnect keyless access control unit connector A, the 32P connector. With connector A disconnected and the rear interior LF antenna 2P connector still disconnected, check continuity on the EXT R+ and EXT R- lines. For EXT R+, check between keyless access control unit connector A No. 31, the PNK wire, and rear interior LF antenna 2P connector No. 2, the WHT wire. For EXT R-, check between keyless access control unit connector A No. 15, the PUR wire, and rear interior LF antenna 2P connector No. 1, the LT GRN wire. If there is continuity, replace the keyless access control unit. If there is no continuity, repair the open or high resistance in the wire.
Wrap-up
The logic is straightforward: confirm B1664, command the rear cabin antenna circuit, then prove whether the fault is at the antenna, in the wiring, or back at the keyless access control unit. For more diagnostic training, visit stepdiagnostics.com.
Final check
Confirm the code first, then use the antenna output and continuity checks to separate an antenna issue from wiring or control unit concerns.
For more guided automotive diagnostics, visit STEP Diagnostics.
