What this code means
B1662 may mean the body control module is detecting an open condition in the middle interior LF antenna circuit used by the keyless access system.
What the vehicle may do
- The vehicle may have keyless access or push-button start detection concerns.
- Interior key detection may be inconsistent or not work as expected.
Possible fault areas
- Possible wiring or connector concern in the middle interior LF antenna circuit.
- Possible body control module side circuit concern.
- Possible middle interior LF antenna concern.
Diagnostic path
Opening context
On this Civic, B1662 points to the middle interior LF antenna circuit being seen as open by the body control module. In plain terms, the car may not be seeing that interior key antenna circuit the way it should, so keyless access or push-button start behavior can be affected. The likely fault areas are the antenna circuit wiring or connectors, the body control module side of the circuit, or the middle interior LF antenna itself. Before diving into the pinpoint checks, start with the basic system checks and follow a structured diagnostic approach. If other codes are present, understand what they mean first, then come back to B1662 with a clean direction.
Scan tool starting point
Begin with the HDS self check. Go into One-Push Start, then Keyless Access Control Unit, and run Self Check. That gives you the current system picture before you start unplugging connectors or chasing the open circuit.
External circuit open-wire checks
For the EXT_R plus and EXT_R minus open-wire inspection, turn IG Mode OFF. Disconnect the middle interior LF antenna 2P connector, then disconnect body control module connector C, the 66P connector. With those disconnected, check the EXT_R plus side of the circuit at the specified probe points. A normal result is less than 1 Ω. Then check the EXT_R minus side the same way. A normal result there is also less than 1 Ω. If either side is abnormal, treat this as a circuit problem and stay with the wiring and connection path before moving on.
Module-side check
Only move into the module-side check once the external circuit has tested normal. There is a way to run the module check earlier in the process, but if that check fails, do not jump straight to a conclusion. Continue the individual checks so you know exactly which part of the path failed. For the module-side setup, disconnect the middle interior LF antenna 2P connector. Then run the internal circuit inspection with IG Mode ON. The normal condition is voltage. Also pay attention to the permanent power supply note tied to vehicle mode ON or OFF, LOCK. If this inspection is abnormal, the problem is with the body control module side of the system.
Remaining antenna decision
If the external circuit checks normal and the module-side inspection checks normal, then the remaining fault area is the middle interior LF antenna. At that point, the diagnosis has narrowed B1662 away from the wiring path and the module-side check, leaving the antenna as the cause identified by the test path.
Verification and takeaway
After the fault is corrected, keep verification separate from the testing steps: clear the code, operate the system, and confirm B1662 does not return. The key point is to prove the open circuit path first, then move to the module-side check, and only leave the antenna as the answer after the other checks are normal. For more diagnostic training, visit stepdiagnostics.com.
Final check
Follow the circuit checks in order, confirm the module-side result, and only blame the antenna after the other inspection items are normal.
For more guided automotive diagnostics, visit STEP Diagnostics.
