Code Definition

B1218 — Horn Relay Coil Circuit Short to Vbatt

System: Body  |  Type: Manufacturer-Specific  |  Make: Generic

About B1218

B1218 is a manufacturer-specific body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1218 is stored, the module has detected a short-circuit (voltage pulled to ground or to supply) in the monitored circuit.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

B1218 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The Body Control Module (BCM) energises the horn relay coil through an internal low side driver whenever a horn request is received from the steering wheel horn switch, the alarm system panic function, or the remote keyless entry panic button. DTC B1218 is set when the BCM detects that the horn relay coil control wire is bridged to battery voltage, preventing the driver from pulling the coil low side to ground and energising the relay. Because the BCM monitors current through its low side driver and expects to see ground level voltage during an on command, a direct short to battery creates an ...

Join TaT to view the complete code information and diagnostic details.

Quick Facts