C1264 — Lamp Warning Relay Circuit Short To Battery #

Note: The wording of this DTC may differ depending on the vehicle’s manufacturer. See below for known label variations by OEM.

• “Lamp Warning Relay Circuit Short to B+” (Toyota, Lexus)
• “Lamp Outage Relay Input Circuit High” (Mazda)
• “Warning Lamp Relay Control Circuit High” (Kia, Hyundai)

Summary of Code C1264 #

The C1264 DTC indicates that the lamp warning relay circuit—the electrical pathway responsible for activating a dashboard warning or exterior lamp—has detected a short to battery voltage. In this context, a relay is an electrically operated switch, and a “short to battery” means the circuit is receiving constant voltage from the battery, even when it should not. This can lead to incorrect operation of warning lamps, potentially masking other faults or creating false alerts. The code is most often associated with ABS, traction control, or bulb-out warning systems, depending on the vehicle. Prompt diagnosis is needed to ensure that safety warning indicators function correctly.

Common Symptoms for Code C1264 #

Drivers and technicians may notice various symptoms if the C1264 code is present. While some may be subtle, others can be quite noticeable, especially if the warning system is critical to safe operation. Typical symptoms include:

• Warning lamp illuminated on the dashboard (such as ABS, traction, or lamp-out warning)
• Warning lamp stays on constantly, even when the underlying condition is resolved
• Warning lamp does not illuminate when expected during the key-on/self-test phase
• Intermittent chimes or alerts related to the affected warning system
• In some cases, malfunction of related systems (e.g., ABS or traction control disabled)

Probable Causes for Code C1264 (Most Common First) #

The C1264 code is most often caused by electrical faults, but the root cause can vary. Diagnosing the most likely reason first is the fastest way to an accurate repair. Here are the typical causes, listed in order of likelihood:

1. Shorted wiring between the warning relay and the battery or fuse block
2. Failed relay (internal short causing constant voltage output)
3. Corroded or contaminated relay socket (causing unintended current path)
4. Incorrectly installed aftermarket components (such as alarm or lighting kits tapping into the warning lamp circuit)
5. Faulty control module (such as the ABS or Body Control Module sending improper voltage)

Step-by-Step Diagnosis for Code C1264 #

Diagnosing C1264 requires a methodical approach to avoid unnecessary part replacement and to ensure proper repair. Follow these steps for a professional result:

• Check for additional DTCs with a scan tool and address any related codes first.
• Inspect the affected warning lamp circuit visually for obvious shorts, damage, or aftermarket wiring.
• Test the lamp warning relay by removing it and checking for continuity across the coil and switch pins according to the OEM wiring diagram.
• Probe the relay socket for battery voltage and ground where appropriate, ensuring no pins show voltage when the system is off.
• Check wiring continuity between the relay, battery, and control module using a multimeter. Look for shorts to power or ground.
• Substitute a known good relay (if available) to rule out internal relay failure.
• If all else checks out, suspect a faulty control module and follow OEM-specific test procedures for module output diagnostics.

Possible Repairs for Code C1264 #

Once the root cause is identified, apply the appropriate fix. The following repairs correspond to the most common causes:

• Repair or replace damaged wiring and connectors in the lamp warning relay circuit.
• Replace a faulty warning relay with an OEM-approved part.
• Clean or repair a corroded relay socket and ensure a tight fit for all pins.
• Remove or correct aftermarket wiring affecting the warning lamp circuit. Use proper splicing and insulation techniques.
• If confirmed, replace or reprogram the affected control module per the OEM’s diagnostic flowchart.

Is It Safe to Drive with Code C1264? #

Driving with an active C1264 code is not recommended. While your vehicle may remain operable, you risk losing accurate warning indicators for critical systems such as ABS, traction control, or exterior lighting. This could lead to safety hazards if another fault occurs and you are not alerted. It is best to address the issue promptly to ensure all safety systems are correctly monitored.

Vehicles Most Commonly Affected by Code C1264 #

This code is most frequently seen in vehicles equipped with advanced warning lamp monitoring systems, especially those from Japanese and Korean manufacturers. The following models have reported C1264 occurrences:

• Toyota Camry, Corolla, Highlander
• Lexus ES, RX, IS
• Mazda 3, 6, CX-5
• Hyundai Sonata, Elantra, Santa Fe
• Kia Optima, Sorento, Forte

Common Mistakes & Best Practices for Code C1264 #

Too often, technicians and DIYers misdiagnose or overlook the true cause of C1264, leading to repeat failures. Avoid these errors and follow these best practices:

• Do not replace the relay or module before thoroughly checking wiring and connectors for shorts or corrosion.
• Always use the OEM wiring diagram for your specific vehicle to identify proper pin locations and voltages.
• Do not ignore aftermarket modifications; improper installations are a common source of this code.
• After repairs, clear the DTC and retest the warning lamp operation with a scan tool.
• Document all findings and repairs for future reference and warranty purposes.

Express FAQ for Code C1264 #

Still have questions? Here are quick answers to what vehicle owners and technicians most often ask:

• Q: Will C1264 cause my car to fail inspection?
  A: In many states, yes. If a warning lamp is malfunctioning due to this code, your vehicle could fail a safety or emissions inspection.
• Q: Can I just replace the relay to fix C1264?
  A: Not always. While a bad relay is common, wiring issues or control module faults are also frequent. Always diagnose before replacing parts.