B1373 — Illuminated Entry Relay Short To Battery #

Note: The code label may vary depending on the vehicle manufacturer.

• Illuminated Entry Relay Circuit Short to Battery (Ford, Lincoln, Mercury)
• Entry Light Relay Circuit High (Mazda)
• Interior Lamp Relay Shorted to Battery (General Motors)

Summary of code B1373 #

The B1373 diagnostic trouble code (DTC) indicates a problem with the illuminated entry relay circuit, specifically a short to battery voltage. The illuminated entry relay is an electronic switch that controls the vehicle’s interior lights when entering or exiting the vehicle. A “short to battery” means that a wire or relay terminal is receiving full battery voltage when it shouldn’t, likely due to damaged wiring or a faulty relay. This issue is typically detected by the body control module (BCM), which monitors the state of related circuits. If not addressed, this fault can lead to unwanted battery drain or malfunctioning interior lights. Early diagnosis is essential to avoid more complex electrical issues or inconvenience.

Common symptoms for code B1373 #

A short to battery in the illuminated entry relay circuit can produce a variety of symptoms, from mild inconvenience to noticeable electrical issues. Typically, drivers may observe abnormal behavior from their vehicle’s interior lighting system. The most frequent symptoms include:

• Interior dome lights remain on when they should turn off
• Interior lights do not respond to door opening/closing
• Battery drain or dead battery after the vehicle sits unused
• Illuminated entry feature not functioning properly
• BCM or security system warning lights illuminated

Probable causes for code B1373 #

The most common causes for a B1373 code involve issues with the relay, wiring, or related connectors. These are listed below in order of likelihood:

1. Shorted illuminated entry relay (internal fault)
2. Damaged or frayed wiring harness in the illuminated entry circuit
3. Corroded or loose connection at relay or associated connectors
4. BCM malfunction (less common)
5. Aftermarket accessory tap-in causing unwanted voltage to the circuit

Step-by-step diagnosis for code B1373 #

Diagnosing a B1373 code requires a methodical approach to rule out each possible cause. Here’s a recommended step-by-step process:

• Use a scan tool to confirm B1373 and check for related codes.
• Inspect the illuminated entry relay and its socket for signs of overheating or corrosion.
• Check the relay function by swapping with a known good relay if possible.
• Visually inspect wiring from the BCM to the relay for damage, pinching, or exposed wires.
• Test the circuit for continuity and voltage with a digital multimeter (DMM).
• Check all ground points for cleanliness and tightness.
• If all physical checks pass, use wiring diagrams to trace the circuit and ensure no aftermarket devices are interfering.
• If the issue persists, consider BCM diagnostics or reprogramming (consult OEM service info).

Possible repairs for code B1373 #

Repair solutions for a B1373 code are directly linked to the root cause found during diagnosis. Here are the most common fixes:

• Replace the illuminated entry relay if it tests faulty.
• Repair or replace damaged or shorted wiring in the circuit.
• Clean and secure all connectors involved in the illuminated entry circuit.
• Remove or reroute aftermarket accessories causing interference.
• In rare cases, repair or replace the BCM after confirming all other components are functional.

Is it safe to drive with code B1373? #

Limited: While code B1373 does not directly affect vehicle safety or drivability, it can lead to parasitic battery drain. If the interior lights remain on, you risk finding your battery dead after parking for extended periods. Avoid leaving the vehicle unused or parked with the code active. Address the issue promptly to prevent inconvenience or potential immobilization.

Vehicles most commonly affected by code B1373 #

This DTC is seen most often on vehicles where the illuminated entry feature is controlled via a dedicated relay and monitored by the BCM. It is especially prevalent on certain Ford, Lincoln, Mercury, and Mazda models from the late 1990s to mid-2010s, as well as some General Motors vehicles.

• Ford F-150, Explorer, Taurus (various years)
• Lincoln Town Car, Navigator
• Mercury Grand Marquis, Sable
• Mazda 6, Tribute
• Chevrolet Silverado, Suburban (GM trucks/SUVs with illuminated entry)

Common mistakes & best practices for code B1373 #

When troubleshooting a B1373 code, it’s easy to overlook simple causes or jump to conclusions. Here are some frequent errors and tips to avoid them:

• Replacing the relay without inspecting wiring or connectors
• Ignoring aftermarket alarm or remote start installations that may affect the circuit
• Overlooking signs of water intrusion or corrosion in relay sockets
• Failing to clear codes and retest after each repair step
• Not consulting OEM wiring diagrams for accurate circuit tracing

Quick FAQ about code B1373 #

Still have questions? Here are answers to some of the most common concerns about the B1373 code:

• Q: Can a B1373 code drain my battery overnight?
  A: Yes, if the interior lights stay on due to a stuck relay or shorted wire, your battery can discharge completely.
• Q: Do I need special tools to fix B1373?
  A: Basic tools like a digital multimeter and a scan tool are usually sufficient. For complex cases, access to OEM wiring diagrams is recommended.
• Q: Will replacing the relay always fix B1373?
  A: Not always. If wiring is damaged or connectors are corroded, the problem can persist even after replacing the relay.