What this code means
B1658 may indicate that the keyless access control unit is detecting a possible open condition in the rear bumper LF antenna circuit.
What the vehicle may do
- Keyless access operation near the rear of the vehicle may be inconsistent.
- The system may have trouble recognizing keyless access activity in the rear bumper area.
Possible fault areas
- Rear bumper LF antenna circuit
- EXT_TR+ and EXT_TR- wiring
- Connector fit or terminal condition
- Keyless access control unit
Diagnostic path
What B1658 is telling you
On this Civic, B1658 points to a possible open-circuit fault in the rear bumper LF antenna circuit for the keyless access control unit. In plain terms, the system may not be seeing the rear bumper antenna circuit the way it expects to. The driver may notice keyless access behavior around the rear of the vehicle that is inconsistent or does not respond normally. The broad fault areas can include the rear bumper LF antenna, the EXT_TR+ and EXT_TR- wiring, connector fit or terminal condition, and, after the circuit proves good, the keyless access control unit itself.
Start by confirming the code
Start with the basic system checks. Clear the DTCs with the HDS. Then select the keyless access control unit from the one-push start system menu, enter self check, run the self check, and check for DTCs again. If B1658 comes right back, continue to the rear bumper antenna circuit test. If B1658 is not indicated, treat it as an intermittent condition for now. The system is OK at this time, so concentrate on loose or poor connections before going deeper.
Check the control unit output at the rear bumper antenna connector
Next, check whether the keyless access control unit is sending output on the EXT_TR+ and EXT_TR- lines. Press the engine start/stop button to select the OFF mode, then disconnect the rear bumper LF antenna 2P connector. Press the engine start/stop button again to select the ON mode. In the HDS, select keyless access control, enter functional tests, and connect the voltmeter between rear bumper LF antenna 2P connector No. 1, the LT BLU wire, and No. 2, the GRY wire. Then run the trunk, tailgate, rear bumper antenna L DC output test. If there is voltage, the path points to the rear bumper LF antenna, and the directed repair is to replace the rear bumper LF antenna. If there is no voltage, keep going and test the wiring between the control unit and the antenna connector.
Check the EXT_TR wiring for an open
For the open-wire check, put the vehicle back in OFF mode. Leave the rear bumper LF antenna 2P connector disconnected, and disconnect keyless access control unit connector A, 32P. Now check continuity on both circuits. For EXT_TR+, check between keyless access control unit connector A, 32P, No. 24, the LT BLU wire, and rear bumper LF antenna 2P connector No. 1, the LT BLU wire. For EXT_TR-, check between keyless access control unit connector A, 32P, No. 8, the GRY wire, and rear bumper LF antenna 2P connector No. 2, the GRY wire. If both circuits have continuity, the EXT_TR+ and EXT_TR- wires are OK, and the directed repair is to replace the keyless access control unit. If there is no continuity, repair the open or high resistance in the affected wire.
Takeaway
The clean way through B1658 is to prove the fault in order: confirm the code, check for control-unit output at the rear bumper antenna connector, then prove the two antenna wires before condemning a component. Do not jump past the circuit checks. For more diagnostic training, visit stepdiagnostics.com.
Final check
This code is often handled best by proving whether the issue is in the antenna, the two-wire circuit, or the control unit before making a repair decision.
For more guided automotive diagnostics, visit STEP Diagnostics.
