C0023 — Stop Lamp Control (Subfault) #

Note: The code definition may vary depending on the vehicle manufacturer (OEM). Below are some known label variations:

• Stop Lamp Control Circuit (Subfault) — Ford
• Brake Light Control Circuit Malfunction — General Motors
• Stop Light Relay Control Error — Toyota
• Brake Lamp Switch Control Circuit — Nissan
• Stop Signal Control Abnormal — Hyundai/Kia

Summary of Code C0023 #

The C0023 code relates to the stop lamp control circuit, indicating an issue detected by the vehicle’s brake system controller—often the ABS (Anti-lock Braking System) module. This code typically points to a problem with the electrical pathway that manages the brake (stop) lights, such as a faulty switch, relay, wiring, or control module. When this code is set, the stop lamps might not function correctly, which is a safety concern. The code may appear as a “subfault,” meaning the system has detected a specific, detailed error within the broader control circuit. Prompt diagnosis and repair are recommended to maintain safe braking and regulatory compliance.

Common Symptoms for Code C0023 #

When C0023 is active, the most noticeable symptom is often abnormal behavior of the brake (stop) lights. Depending on the nature of the subfault, you may experience one or more of the following issues:

• Brake lights not illuminating when the pedal is pressed
• Brake lights stuck on, even when the pedal is released
• ABS warning light or other brake system indicators on the dashboard
• Cruise control disengages or won’t set
• Traction control or stability control warning lights (in some models)

Probable Causes for Code C0023 (in Order of Likelihood) #

Several factors can trigger the C0023 code, but some are more common than others. Here’s a ranked list based on frequency:

1. Faulty brake (stop) lamp switch — The switch that detects brake pedal movement may be worn, misaligned, or failed.
2. Damaged or corroded wiring/connectors — Breaks, shorts, or corrosion in the wiring between the brake lamp switch, ABS module, or rear lights are common.
3. Defective stop lamp relay — Some vehicles use a relay to manage brake light current, which may fail or stick.
4. Burnt-out bulbs or LED assemblies — Multiple failed bulbs or faulty LED circuits can confuse the control module.
5. Faulty ABS or BCM (Body Control Module) — In rare cases, the module responsible for monitoring and controlling the circuit may be at fault.

Step-by-Step Diagnostic for Code C0023 #

Diagnosing C0023 requires a systematic approach. Here’s a step-by-step guide for technicians and advanced DIYers:

• Verify the code with a diagnostic scan tool; confirm whether it’s current or history.
• Visually inspect brake lights for function when the pedal is pressed and released.
• Check all brake lamp bulbs (or LED assemblies) for operation and correct type/fitment.
• Test the brake lamp switch at the pedal for proper operation and continuity with a multimeter.
• Inspect wiring and connectors along the stop lamp circuit for damage, corrosion, or looseness.
• If equipped, check the stop lamp relay for proper function.
• Clear the code and see if it returns after repairs or bulb replacement.
• If the issue persists, test the ABS or BCM outputs (may require OEM-specific scan tool and wiring diagrams).

Possible Repairs for Code C0023 #

Once the root cause is identified, repairs should target the specific failure. Here are common fixes associated with C0023:

• Replace a faulty brake lamp switch and adjust it per OEM specifications
• Repair or replace corroded, broken, or shorted wiring/connectors in the stop lamp circuit
• Replace a defective stop lamp relay (if present)
• Install new bulbs or LED lamp assemblies as required
• Update or replace the ABS/BCM module if found to be defective (rare, verify with proper testing)

Can You Drive with Code C0023? #

It is not recommended to drive with code C0023 active. In most cases, brake lights are not functioning correctly, which is a major safety hazard and typically illegal. Other vehicle systems—like ABS, traction control, and cruise control—may also be disabled or impaired. Immediate attention is necessary to ensure your vehicle is safe and road-legal.

Vehicles Most Commonly Affected by Code C0023 #

While C0023 can appear on a variety of modern vehicles, it is most often reported on models from:

• Ford (especially Fusion, Focus, F-150, Escape)
• General Motors (Chevrolet Malibu, Silverado, GMC Sierra)
• Toyota (Camry, Corolla, Tacoma)
• Nissan (Altima, Sentra, Rogue)
• Hyundai/Kia (Sonata, Elantra, Sorento)

However, this code may occur in any vehicle using networked brake light control via a central module.

Common Mistakes & Best Practices for Code C0023 #

A few pitfalls can prolong diagnosis or cause repeat failures with C0023. Here’s how to avoid them:

• Assuming the problem is only a blown bulb—always check the entire circuit.
• Overlooking the brake lamp switch adjustment—incorrect alignment can cause intermittent faults.
• Neglecting to inspect connectors for corrosion, especially in humid climates.
• Not verifying repairs by clearing codes and retesting lamp function.
• Skipping OEM wiring diagrams or pinouts—essential for complex, module-controlled systems.

Quick FAQ for Code C0023 #

Q: Will a blown brake light bulb always trigger C0023?
A: Not always. Some vehicles set this code only if multiple bulbs fail or if the control circuit loses feedback entirely.

Q: Can a DIYer fix C0023, or is dealer service required?
A: Many causes—like bulb or switch replacement—are DIY-friendly. However, if module testing or programming is needed, dealer-level tools and expertise may be required.