Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2021 Honda Civic EX-LFACTORY OEM SERVICE PROCEDURE
Keyless Access Control Unit (Body Control Module)
| DTC | Description | DTC type |
|---|---|---|
| B1601 | Keyless access control unit (body control module) internal (CPU) error | Internal error |
| DTC | Description | DTC type |
|---|---|---|
| B1602 | Keyless access control unit (body control module) internal (EEPROM) error | Internal error |
| B1632 | MTR CONT signal error | Signal error |
| B1640 | RF unit not connected | Signal error |
| B1645 | Driver's door LF antenna circuit short | Signal error |
| B1646 | Driver's door LF antenna circuit open | Signal error |
| B1647 | Passenger's door LF antenna circuit Short | Signal error |
| B1648 | Passenger's door LF antenna circuit open | Signal error |
| B1657 | Rear bumper LF antenna circuit short | Signal error |
| B1658 | Rear bumper LF antenna circuit open | Signal error |
| B1659 | Front interior LF antenna circuit short | Signal error |
| B1660 | Front interior LF antenna circuit open | Signal error |
| B1663 | Rear interior LF antenna circuit short | Signal error |
| B1664 | Rear interior LF antenna circuit open | Signal error |
| B1667 | 2/4-door: Rear shelf LF antenna circuit short | Signal error |
| 5-door: Rear shelf LF antenna (middle interior LF antenna) circuit short | ||
| B1668 | 2/4-door: Rear shelf LF antenna circuit open | Signal error |
| 5-door: Rear shelf LF antenna (middle interior LF antenna) circuit open | ||
| U1280 | B-CAN communication bus line error (BUS-OFF) | Loss of communication |
| U1281 | Keyless access control unit (body control module) lost communication with MICU (body control module) | Loss of communication |
| U128D | Keyless access control unit (body control module) lost communication with gauge control module | Loss of communication |
Factory Service Tools
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.