What Does B1217 Mean?
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected an electrical fault in the horn relay coil circuit. The BCM monitors the control side of the horn relay and has identified either an open circuit, short to ground, short to power, or excessive resistance preventing proper relay operation. This prevents the horn from functioning when the horn button is pressed.
Common Causes
35%
Failed horn relay with open or shorted coil winding
30%
Damaged wiring or corroded connections between BCM and horn relay
20%
Faulty BCM output driver circuit for horn relay control
10%
Blown fuse or poor power/ground supply to horn relay
5%
Water intrusion or corrosion in relay socket/mounting location
Diagnostic Steps
1
Step 1: Locate the horn relay (typically in underhood or interior fuse/relay box) and visually inspect for physical damage, corrosion, or burnt terminals. Remove relay and inspect socket for corrosion or pushed-back terminals.
2
Step 2: Using a multimeter, measure resistance across the relay coil terminals (typically 70-120 ohms for most automotive relays). If open circuit or significantly out of range, replace relay.
3
Step 3: Check for voltage at the relay socket power supply pin (typically battery voltage) and verify good ground continuity (less than 1 ohm resistance to chassis ground) at the ground pin.
4
Step 4: With relay removed and ignition on, press horn button while measuring voltage at the BCM control wire terminal in relay socket. Should see voltage switching (0V to 12V or vice versa). No switching indicates BCM fault or open control circuit.
5
Step 5: Inspect wiring harness from BCM to relay socket for chafing, pinching, or damage. Pay special attention to areas where harness passes through bulkheads or near sharp edges. Check all connector pins for corrosion and proper terminal tension.
6
Step 6: After repairs, clear codes and activate horn multiple times to verify proper operation. Monitor live data for horn relay command status to confirm BCM is properly controlling the circuit.
Estimated Repair Cost
$75 - $350
Parts + labor, varies by vehicle and location
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected an electrical fault in the horn relay coil circuit. The BCM monitors the control side of the horn relay and has identified either an open circuit, short to ground, short to power, or excessive resistance preventin...
The most common cause of B1217 (Horn Relay Coil Circuit Failure) is: Failed horn relay with open or shorted coil winding
Typical repair costs for B1217 range from $75 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive, but the horn will not function, eliminating an important safety warning device. Repair should be completed promptly as the horn is legally required equipment in most jurisdictions and needed for emergency signaling.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1217 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical System
Difficulty
Type
Manufacturer
Recommended Tools
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