B1373 — Illuminated Entry Relay Short To Battery

The diagnostic trouble code (DTC) B1373 indicates a problem related to the illuminated entry relay being shorted to the vehicle’s battery. In simple terms, this means there is an electrical issue affecting the relay responsible for controlling interior lighting, potentially leading to system malfunctions or electrical faults. It’s important to note that labels and coding may vary between manufacturers, but the underlying problem remains similar across different vehicle makes.

Manufacturer variations for trouble code B1373

Different vehicle manufacturers might assign different labels or codes for similar issues related to the illuminated entry relay system. While the core function remains consistent, the exact DTC may vary depending on the OEM (Original Equipment Manufacturer). Here are some known variations:

• Ford: B1373 or B1373A
• GM (Chevrolet, Opel, Vauxhall): Often B1373 or a related code in the body control module (BCM) diagnostics
• Volkswagen/Audi: Might reference specific relay faults under different code labels, but B1373 is recognized in some models
• Hyundai/Kia: Similar codes may be used, sometimes in the P-series range, but B1373 may be applicable in certain contexts

What does trouble code B1373 mean?

The B1373 code primarily pertains to a fault in the illuminated entry relay circuit. The ECU (Electronic Control Unit), which manages various electronic systems within the vehicle, has detected that the relay responsible for powering the interior lights or entry system is either shorted or malfunctioning due to a direct short circuit to the battery voltage.

During diagnostics, the ECU monitors the relay’s electrical state. When it detects a short to the battery, it triggers the code to alert the driver and technician that a wiring or relay fault exists. This problem is often seen when the relay’s wiring insulation is compromised, or the relay itself has failed internally.

This fault can manifest during normal vehicle operation, especially when interior lighting, door entry systems, or related circuits are in use. The cause for the fault may be environmental (moisture, corrosion), mechanical (relay contact failure), or electrical (incorrect wiring or component damage).

Severity and risks of trouble code B1373

The severity of the B1373 code is generally considered moderate. While it does not typically prevent the vehicle from being driven, it indicates an electrical fault that could impact the vehicle’s interior lighting, power systems, or safety features linked to the entry system. If left unaddressed, this fault can lead to additional electrical issues, such as blown fuses, degraded wiring, or damage to the relay and surrounding components.

**Potential risks include:**

• Flickering or non-functioning interior lights
• Unintended activation or deactivation of electrical circuits
• Possible drain on the battery due to short circuit
• Electrical damage if the short is severe or ongoing

**Can the vehicle be driven?** Limited — Generally, yes. The vehicle can often be driven safely, but addressing the fault promptly is recommended to prevent further electrical damage or inconvenience.

Symptoms of trouble code B1373

When B1373 is active, you might notice several signs related to electrical system irregularities, particularly involving lighting. These are some common symptoms:

• Interior lights not functioning properly, such as flickering, staying on, or not turning on at all
• Relays clicking or making noise when switching lights or doors
• Dashboard warning or error message related to the electrical system or interior lighting
• Electrical components behaving unpredictably, such as door lock actuators or entry system malfunctions
• Persistent fuse blows in circuits related to interior lighting or entry systems

Most likely causes of trouble code B1373

Understanding the root causes of the B1373 fault aids in efficient diagnosis and repair. While specific circumstances vary, these are the most common causes, ranked in order of likelihood:

1. Shorted or damaged relay: The relay itself may have internal faults, causing a direct short circuit to the battery voltage. This is the most common cause and often straightforward to detect.
2. Wiring insulation damage or corrosion: Wires connecting the relay or associated circuits may be compromised, exposing conductors and creating a short circuit.
3. Faulty or improperly installed wiring: Incorrect wiring, loose connections, or improper grounding can lead to short circuits.
4. Malfunctioning body control module (BCM) or related controllers: If the control modules have internal faults, they may incorrectly monitor or activate the relay circuitry.
5. Environmental factors: Exposure to moisture, dirt, or physical damage can cause shorts or corrosion within relay sockets or wiring harnesses.

How to diagnose trouble code B1373

Diagnosing B1373 requires a systematic and safe approach. The following steps are generic and applicable across most vehicles, with the goal to identify whether a relay or wiring fault exists:

1. Visual inspection: Check the relay, wiring harnesses, and connectors for obvious signs of damage, corrosion, or wear. Look for melted insulation, loose connections, or signs of water ingress.
2. Check the relay: Remove the relay and inspect it for physical damage or test it using a relay tester or multimeter. Replace if necessary.
3. Inspect wiring continuity: Use a multimeter to test for continuity in the wiring leading to and from the relay circuit, checking for breaks or shorts.
4. Monitor live data: Connect a suitable scanner or diagnostic tool to monitor the relay’s electrical signals—look for abnormal voltages or patterns that indicate a short circuit.
5. Perform a controlled circuit test: Power supply circuits and relay outputs should be tested in a controlled environment to verify proper operation and identify short circuits or wiring faults.
6. Check the control module: If physical inspections are inconclusive, evaluate the body control module or related controllers for faults or communication issues.

Possible repairs for trouble code B1373

Once the cause has been identified, repairs should be carried out accordingly. Some repairs are simple and suitable for a DIY approach, while others require professional intervention.

• Replacing the relay: If the relay is faulty or internally shorted, replacing it is a basic repair, typically straightforward and quick.
• Repair or replace damaged wiring: Damaged or corroded wiring must be repaired with appropriate insulation or replaced entirely. This repair can be complex but is essential for safety and functionality.
• Correcting wiring installation errors: Ensuring wiring is correctly routed, insulated, and grounded reduces short circuit risks. Professional wiring repair or re-routing may be necessary.
• Replacing or reprogramming control modules: If the fault lies in the control unit, specialist diagnostics and repairs are recommended, often involving reprogramming or replacement.
• Addressing environmental factors: Cleaning and protecting wiring harnesses from moisture and dirt can prevent future faults, a perhaps less technical but beneficial step.

Vehicles commonly associated with trouble code B1373 in Europe

While B1373 is not exclusive to a particular make or model, certain vehicle brands are more frequently reported with this fault. These include models from major manufacturers, especially those with complex electrical systems.

In Europe, common brands include:

• Ford: Focus, Fiesta, Mondeo
• Volkswagen Group: Golf, Polo, Passat, Audi A3
• Opel/Vauxhall: Astra, Corsa
• Hyundai/Kia: i30, Ceed, Sportage

Frequent mistakes with trouble code B1373

During diagnosis and repair, certain mistakes are common among technicians or DIY enthusiasts. Recognising these can improve diagnostics and prevent unnecessary repairs.

• Ignoring visual signs of damage: Failing to inspect wiring and relay physically can lead to misdiagnosis.
• Replacing parts without proper testing: Replacing relays or wiring without confirming they are faulty wastes time and resources.
• Overlooking environmental factors: Moisture or corrosion can cause faults but are sometimes overlooked.
• Misinterpreting codes or labels: Assuming the code is the only cause—other electrical issues may mimic B1373 symptoms.
• Skipping live data checks: Relying solely on code reading without real-time testing might miss intermittent faults.

FAQ — trouble code B1373

Can this code disappear on its own? Not usually. Electrical faults like a short circuit typically persist unless repaired. Sometimes, temporary issues or wiring contacts may seem to resolve but can reoccur.

Can I keep driving? Usually, yes. The vehicle often remains operational, but electrical faults can worsen or cause additional problems, so prompt diagnosis is advisable.

Why does the code return after clearing? This indicates an unresolved root cause, such as damaged wiring or a faulty relay, which re-triggers the fault once the system is reset.