What this code means
B1660 may indicate a problem with the front interior LF antenna circuit used by the keyless access and one-push start system.
What the vehicle may do
- The vehicle may have inconsistent keyless access behavior.
- The push-button start system may not recognize the key as expected.
- The system may store the code during a keyless access control unit self check.
Possible fault areas
- Front interior LF antenna
- Antenna connector or wiring condition
- Keyless access control unit output circuit
- Possible open or high resistance in the related circuit
Diagnostic path
Opening context
On this 2010 to 2015 Honda Civic with the 1.8 gas engine, B1660 points us toward the front interior LF antenna circuit in the keyless access and one-push start system. In plain language, the control unit may not be seeing the front cabin antenna circuit the way it expects. The driver may notice keyless access or push-button start behavior that is inconsistent, or the system may simply store the code during a self check. The broad fault areas can include the front interior LF antenna, its connector and wiring, or the keyless access control unit. We are going to keep the diagnosis focused on B1660 and follow the test path in order.
Confirm the code is current
Start by verifying the problem with the HDS. Clear the DTCs. From the ONE-PUSH START system menu, select the KEYLESS ACCESS CONTROL UNIT, enter SELF CHECK, run the self check, and then check the DTCs again. If B1660 comes right back, continue into the circuit test. If B1660 does not come back, treat it as an intermittent fault for now. The system is OK at this time, so concentrate on loose or poor connections before going any deeper.
Check control unit output to the antenna circuit
With B1660 confirmed, check the keyless access control unit output on the EXT_F plus and EXT_F minus lines. Press the engine start/stop button to select OFF mode, then disconnect the front interior LF antenna 2P connector. Next, press the engine start/stop button to select ON mode. On the HDS, go into KEYLESS ACCESS CONTROL under the ONE-PUSH START system, enter FUNCTIONAL TESTS, and set up a voltmeter between the front interior LF antenna 2P connector No. 1, the BRN wire, and connector No. 2, the GRN wire. Then select CABIN FRONT ANTENNA L DC OUTPUT with the HDS. If there is voltage, the diagnostic path calls for replacing the front interior LF antenna. If there is no voltage, move on to checking the wiring for an open.
Check the EXT_F lines for an open
For the open-wire check, put the system back in OFF mode and disconnect keyless access control unit connector A, the 32P connector. The front interior LF antenna 2P connector stays disconnected for this test. Check continuity on both circuits. For EXT_F plus, check between keyless access control unit connector A 32P No. 32, the GRN wire, and front interior LF antenna 2P connector No. 2, also the GRN wire. For EXT_F minus, check between keyless access control unit connector A 32P No. 16, the BRN wire, and front interior LF antenna 2P connector No. 1, also the BRN wire. If both lines have continuity, the EXT_F plus and EXT_F minus wires are OK, and the diagnostic path calls for replacing the keyless access control unit. If there is no continuity, repair the open or high resistance in the wire.
Takeaway
The key on B1660 is not to jump straight to a module. First confirm the code is current, then see whether the antenna is being driven, and only then prove whether the EXT_F plus and EXT_F minus circuits are open or intact. For more diagnostic training, visit stepdiagnostics.com.
Final check
B1660 is best approached by confirming the code first, then separating an antenna issue from a wiring issue or control unit output issue.
For more guided automotive diagnostics, visit STEP Diagnostics.
