B1371 — Illuminated Entry Relay Circuit Failure

What does OBD2 code B1371 mean?

OBD2 code B1371 flags a problem with the body electrical system (illuminated entry relay circuit failure). The car is usually drivable while you plan the repair. Common culprits: faulty switch, motor or actuator of the affected system, blown fuse or failed relay, body control module (BCM) fault.

How do I diagnose B1371 myself?

Start with a scan: confirm B1371, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the illuminated entry relay circuit, and verify the suspect component against live data before buying parts.

What are the symptoms of B1371?

Drivers most often notice: the affected function (locks, windows, lighting, wipers) works intermittently or not at all, warning light on the dashboard, no impact on engine operation in most cases.

Is it safe to drive with B1371?

Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

How much does it cost to fix B1371?

Replace the switch or actuator — $120–$450; BCM repair or replacement — $300–$900; Repair wiring or connectors — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

When your vehicle's control module logs code B1371, it's flagging a problem in the body electrical system — specifically, the illuminated entry relay circuit. This isn't an engine or drivetrain issue. The illuminated entry feature controls interior lighting that activates when you unlock or open a door, and it often ties into the power lock system. When the relay responsible for this function stops responding correctly, the module detects the abnormality and stores B1371.

The control module continuously monitors voltage and ground signals at the illuminated entry relay. It expects certain readings when it commands the relay on or off. When those readings fall outside the expected range — an open circuit, a short to battery, or a short to ground — the module logs B1371 and captures a freeze frame snapshot. That snapshot records RPM, engine load, coolant temperature, and vehicle speed at the exact moment the fault occurred. Technicians use this data to recreate the failure conditions during testing.

Most of the time, B1371 has no impact on how your car drives. The engine, transmission, and core safety systems don't depend on the illuminated entry circuit. You may not even notice the problem until you try to unlock your vehicle and the interior lights fail to come on, the door locks don't respond, or a dashboard warning appears. In most cases, you can continue driving normally while you arrange a repair.

Common Symptoms of B1371

• The interior lighting does not activate when the doors are unlocked or opened
• Power door locks fail to operate or respond only intermittently
• The dashboard displays a body system warning light
• Other body functions such as windows, wipers, or exterior lighting behave inconsistently
• No effect on engine performance, throttle response, or braking under normal conditions

What Causes B1371

• Blown fuse or failed relay in the illuminated entry circuit
• Damaged wiring in door jambs or areas exposed to moisture and road salt
• Corroded, loose, or contaminated electrical connectors
• Faulty body control module (BCM) unable to process relay commands correctly
• Defective switch, door lock motor, or actuator in the affected system
• Chafed wiring at flex points where wires pass through hinges or body seams

How to Diagnose B1371

1. Connect an OBD2 scanner, confirm B1371 is stored, and record the freeze frame data — it shows engine conditions when the module detected the fault and helps you reproduce the failure during testing.
2. Check for related diagnostic trouble codes. Body system codes often appear together, and the secondary code usually points to the actual failing component rather than the relay circuit itself.
3. Look up manufacturer technical service bulletins for your make, model, and year. Search by VIN on the automaker's website or nhtsa.gov — many B0xxx codes have documented factory fixes or software updates.
4. Perform a visual inspection of the wiring harness and connectors tied to the body electrical system. Check for damaged insulation, moisture intrusion, corrosion on terminals, and pins that are pushed back or bent.
5. Operate the affected function while monitoring live data. Watch switch and motor PIDs on your scanner to confirm the module sends the correct command and the component responds.
6. Pay close attention to wiring at flex points — door jambs, liftgate hinges, and anywhere wires bend repeatedly. Inspect these areas closely. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and verify B1371 does not return.

Repair Options and Costs

Address the least expensive and most common causes before replacing major control modules:

• Repair damaged wiring or corroded connectors: $80–$250
• Replace faulty switch, door lock motor, or actuator: $120–$450
• Repair or replace the body control module: $300–$900

How Much Does It Cost to Fix B1371?

The total depends entirely on what actually failed. Typical parts and labor costs at an independent repair shop in the United States range from $80 to $900. A loose connector or damaged wire is inexpensive to fix. BCM replacement is the high end of the range and is rarely the first thing to check. Spending time on a thorough diagnosis before buying parts almost always saves money — the most expensive scenario is rarely the correct one.

Can You Drive with B1371?

B1371 is classified as short-term safe to drive. Body electrical faults do not typically affect engine operation, braking, or steering. However, certain failures can create safety concerns. If the illuminated entry fault also affects exterior lighting, you may be driving without properly functioning headlights or taillights. Wiper motor issues become hazardous in heavy rain or snow. A central locking fault that prevents the doors from locking could leave the vehicle unsecured. Address the underlying cause promptly and use extra caution if any secondary systems are affected.

Related OBD2 Codes

• B1300: Power Door Lock Circuit Failure
• B1301: Power Door Lock Circuit Open
• B1302: Accessory Delay Relay Coil Circuit Failure
• B1303: Accessory Delay Relay Coil Circuit Open
• B1304: Accessory Delay Relay Coil Circuit Short To Battery
• B1305: Accessory Delay Relay Coil Circuit Short To Ground