B1373

Illuminated Entry Relay Short To Battery

Body Chassis/Safety Entry lighting relay circuit 🟢 Low — Fix at next service ✅ Safe to Drive
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What This Actually Means

In plain language — no jargon

The illuminated entry relay is shorted directly to the vehicle's positive battery voltage, causing it to stay energized constantly. Think of it like a light switch stuck in the ON position due to a broken wire touching the power line.

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Symptoms You May Notice

3 known symptoms for this code
Interior lights remain on continuously or flicker erratically
Battery drains faster than normal when vehicle is parked
Illuminated entry feature does not function properly or is inoperative
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The body control module monitors the illuminated entry relay circuit voltage to ensure it cycles on and off correctly when triggered by door switches or ambient light sensors. The ECU detects an abnormal constant high voltage state that should only occur briefly during entry events, indicating the relay control circuit is shorted to battery voltage.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Relay control voltage 0V-5V cycling with entry events Constant 12V+ presence when relay should be de-energized
Circuit draw during rest 0mA when inactive Sustained current draw indicating stuck relay
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Illuminated entry relay
Locate the relay in the fuse/relay box, remove it, and install a new OEM relay.
2
Wiring harness to relay
Inspect the relay connector and wiring for damaged insulation or pinched wires shorting to battery; repair or replace as needed.
3
Body control module
If relay and wiring are good, the BCM control circuit may be damaged and require professional reprogramming or replacement.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1373 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code B1373

What happens after you fix the fault

Once the fault is repaired, B1373 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.