Illuminated Entry Relay Circuit Malfunction
Diagnostic trouble code B1371 indicates a fault in the illuminated entry relay circuit, which is typically monitored by the Generic Electronic Module (GEM) or Body Control Module (BCM) in Ford and Lincoln vehicles. This relay controls the interior lights that turn on temporarily when the doors are unlocked. The code sets when the module detects an abnormal electrical condition in the relay control circuit, such as an open circuit, short to ground, or short to battery voltage, preventing the courtesy lights from operating correctly during the entry sequence.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty illuminated entry relay with damaged internal contacts
- Open or short circuit in the relay control wiring
- Corroded, loose, or high-resistance connectors or terminals
- Internal failure of the GEM or BCM that controls and monitors the relay circuit
- Blown fuse or voltage drop in the relay power supply line
3. Symptoms You Will Notice
- Interior lights do not turn on when doors are unlocked
- Interior lights stay on continuously or behave erratically
4. Step-by-Step Diagnosis
Check for blown fuses related to the illuminated entry relay and interior lighting.
Inspect the illuminated entry relay for signs of damage or corrosion; test relay operation.
Visually examine wiring and connectors in the relay control circuit for opens, shorts, or corrosion.
Measure voltage and ground at the relay coil and switch terminals per the service manual.
If wiring and relay are good, suspect a faulty GEM/BCM and perform module self-test or replacement.
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, the vehicle is safe to drive. This fault only affects interior courtesy lighting and does not impact engine, transmission, or safety systems.
How much does it cost to fix?▼
Repair costs typically range from $50 to $200 for a relay or fuse replacement, up to $500–$800 if the GEM/BCM module needs replacement.