B0121low severityBody
Theft Deterrent Horn Circuit
on 2017 Chevrolet Impala 3.6L V6 LFX · AWD
What this code means
Malfunction in the theft deterrent horn/siren circuit. The alarm horn or siren does not sound during alarm activation.
Symptoms
- No horn sound during alarm
- Alarm triggers silently
- Horn works normally otherwise
- Security light still flashes during alarm
Common causes
- Faulty alarm siren
- Wiring damage to dedicated siren
- BCM siren output failure
- Siren connector disconnected
Diagnostic steps
- Test alarm siren with direct power
- Check wiring from BCM to siren
- Test BCM siren output
- Inspect siren connector
- Verify siren ground
Repair notes
Replace alarm siren or repair wiring. Check for dedicated siren separate from horn.
Other Body codes on this vehicle
B0001
Driver Frontal Stage 1 Deployment Control
B0001
Driver Frontal Stage 1 Deployment Control
B0002
Driver Frontal Stage 2 Deployment Control
B0002
Driver Frontal Stage 2 Deployment Control
B0003
Passenger Frontal Stage 1 Deployment Control
B0003
Passenger Frontal Stage 1 Deployment Control
B0004
Passenger Frontal Stage 2 Deployment Control
B0004
Passenger Frontal Stage 2 Deployment Control
B0005
Driver Knee Airbag Deployment Circuit
B0005
Driver Knee Airbag Deployment Circuit