What this code means
B1662 may indicate that the body control module is detecting an open condition on the middle interior LF antenna line used by the keyless access and one-push start system.
What the vehicle may do
- The vehicle may have keyless access or start authorization symptoms related to interior antenna detection.
- The concern can be intermittent if the open condition or connector contact issue is intermittent.
Possible fault areas
- Possible antenna circuit wiring or connector issues.
- Possible body control module side circuit issue.
- Possible middle interior LF antenna issue.
Diagnostic path
Opening
On this 2016 to 2024 Honda Civic with the 1.5 turbo, B1662 is tied to the middle interior LF antenna circuit for the keyless access and one-push start system. In plain terms, the body control module may be seeing the middle interior antenna line as open. The driver may notice keyless access or start authorization concerns, and the possible fault areas are the antenna circuit wiring, connector condition, the body control module side of the circuit, or the middle interior LF antenna itself. Start with the basic system checks and keep the diagnosis structured, because this code is about proving where the open circuit is, not guessing at parts.
Start with the scan tool check
Begin by doing the HDS Self Check. That gives you the starting point before you get into pinpoint circuit testing. If other faults are present, understand what they mean first, but keep this path focused on B1662 and the middle interior antenna circuit.
Check the antenna circuit for an open
Next, test the EXT_R plus and EXT_R minus lines for an open. Prepare for that by disconnecting the middle interior LF antenna 2-pin connector, then disconnecting body control module connector C, the 66-pin connector. With IG Mode OFF, check the circuit according to the connector points shown for the test. A normal result on the EXT_R plus open-wire inspection is less than 1 Ω. A normal result on the EXT_R minus open-wire inspection is also less than 1 Ω. If either side is not normal, the problem is in the circuit, so stay with the wiring and connection side of the diagnosis.
Use the combined test note correctly
This test path can be done before the other individual inspections because it includes the inspection items that follow. But if the combined check fails, do not jump ahead. Break the diagnosis back down and test each item individually so you can identify which part of the path failed.
Check the body control module side
Only move into the body control module inspection after the external circuit has been confirmed normal. For that inspection, disconnect the middle interior LF antenna 2-pin connector. Then perform the body control module internal circuit check according to the listed connector points. The listed condition is IG Mode ON, and the normal condition is voltage. The note on this check points out the permanent power supply, so do not treat this like a simple switched-power circuit without confirming the proper connector points first. If this inspection is abnormal, the problem is with the body control module.
Decide what is left
If the open-wire inspection is normal, and the body control module inspection is normal, then the remaining fault callout is the middle interior LF antenna. At that point, the diagnostic path has narrowed the concern away from the circuit and the module-side check, leaving the antenna as the cause identified by this procedure.
Verification and takeaway
Keep verification separate from the pinpoint testing. After the fault found by this path is corrected, verify the repair and confirm B1662 stays gone. The key point on B1662 is simple: prove the middle interior LF antenna circuit first, then check the body control module side, and only call the antenna after the other inspections are normal. For more diagnostic training, visit stepdiagnostics.com.
Final check
This code is often diagnosed by separating the antenna circuit, the module-side check, and the antenna itself instead of guessing at a component.
For more guided automotive diagnostics, visit STEP Diagnostics.
