Engine-CodesGeneric – B251F

B251F Code - High Mounted Stop Lamp Circuit Short to Ground

Quick Answer

The B251F code signifies that the Integrated Control Unit (ICU) has detected a short-to-ground condition in the high mounted stop lamp circuit, which is typically referred to as the center or third brake light. Common causes include Faulty High Mounted Stop Lamp AssemblyHigh Mounted Stop Lamp harness is open or shortedHigh Mounted Stop Lamp circuit has a poor electrical connectionWater intrusion causing corrosion in the wiring or connectorsInternal failure of the Integrated Control Unit (ICU). Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
B251F indicates High Mounted Stop Lamp Circuit Short to Ground.
Common causes
Common causes include Faulty High Mounted Stop Lamp AssemblyHigh Mounted Stop Lamp harness is open or shortedHigh Mounted Stop Lamp circuit has a poor electrical connectionWater intrusion causing corrosion in the wiring or connectorsInternal failure of the Integrated Control Unit (ICU).
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Table of contents Created and updated by William Orellana on Jun 01, 2026
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Code B251F Description

The B251F code signifies that the Integrated Control Unit (ICU) has detected a short-to-ground condition in the high mounted stop lamp circuit, which is typically referred to as the center or third brake light. This component plays a crucial role in vehicle safety by providing an additional visual alert to drivers behind the vehicle when the brakes are applied. When the ICU monitors the brake light circuits, it expects a certain range of current flow. If it detects an excessive current flow or a direct connection to ground, it triggers the B251F code. This can occur due to various reasons, such as a damaged brake light assembly, pinched or frayed wiring, water intrusion that leads to corrosion, or even an internal fault within the lamp itself.

OBDII Code B251F - High Mounted Stop Lamp Circuit Short to Ground
B251F Code - High Mounted Stop Lamp Circuit Short to Ground

Common Causes of B251F

  1. Faulty High Mounted Stop Lamp Assembly
  2. High Mounted Stop Lamp harness is open or shorted
  3. High Mounted Stop Lamp circuit has a poor electrical connection
  4. Water intrusion causing corrosion in the wiring or connectors
  5. Internal failure of the Integrated Control Unit (ICU)

Symptoms of B251F

  1. Engine Light ON (or Service Engine Soon Warning Light)
  2. High mounted stop lamp not illuminating when brakes are applied
  3. Intermittent operation of the center brake light
  4. Increased electrical load on the vehicle's battery
  5. Possible related warning messages on the dashboard

How to Fix B251F

  1. Perform a visual inspection of the high mounted stop lamp assembly for any signs of damage or corrosion.
  2. Check the wiring harness for any pinched, frayed, or broken wires that may be causing a short to ground.
  3. Test the high mounted stop lamp circuit with a multimeter to identify any abnormal voltage readings.
  4. Repair or replace any damaged components, including the lamp assembly or wiring as necessary.
  5. Clear the diagnostic trouble codes and conduct a functional test of the high mounted stop lamp to ensure proper operation.

Cost to Fix B251F

The cost to diagnose and repair a B251F code can vary significantly based on the specific issues found and the labor rates in your area. Typically, parts such as a new high mounted stop lamp assembly can range from $50 to $150, while labor costs can range from $80 to $150 per hour, depending on whether you go to a dealership or an independent shop. Overall, you might expect a total repair cost between $100 and $400, depending on the extent of the repairs needed and the specific make and model of your vehicle.

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Code B251F Information for Specific Makes

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

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