OBD Code B1873: Turn Signal / Hazard Power Feed Circuit Short To Ground

Q: What does OBD code B1873 mean?

Turn Signal / Hazard Power Feed Circuit Short To Ground. The turn signal or hazard light power supply wire is touching ground (metal frame), creating an unwanted electrical short circuit. It's like a water hose with a hole in it—power is leaking out instead of reaching the lights.

Q: What are the symptoms of fault code B1873?

Turn signals or hazard lights not functioning, Dashboard warning light or code display active, Potential blown fuse in the turn signal circuit

Q: How do I fix OBD fault code B1873?

Locate and replace the blown turn signal/hazard fuse in the main fuse box.. Visually inspect turn signal wiring for cuts, abrasions, or damaged insulation that expose bare wire to metal.. Test or replace the turn signal relay/switch if wiring appears intact and fuse keeps blowing.

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What This Actually Means

In plain language — no jargon

The turn signal or hazard light power supply wire is touching ground (metal frame), creating an unwanted electrical short circuit. It's like a water hose with a hole in it—power is leaking out instead of reaching the lights.

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Symptoms You May Notice

3 known symptoms for this code

Turn signals or hazard lights not functioning

Dashboard warning light or code display active

Potential blown fuse in the turn signal circuit

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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The BCM monitors the voltage and current on the turn signal/hazard power feed circuit. When a short to ground occurs, the voltage drops to near 0V and current spikes above normal limits, triggering the fault code.

Voltage & Parameter Thresholds

Parameter	Normal Range	Fault Condition
Power Feed Voltage	12-14V when circuit active	<2V sustained (short to ground detected)
Circuit Current	Normal load current (200-500mA typical)	Excessive current draw or open circuit

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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

Fuse replacement

Locate and replace the blown turn signal/hazard fuse in the main fuse box.

2

Wiring harness inspection

Visually inspect turn signal wiring for cuts, abrasions, or damaged insulation that expose bare wire to metal.

3

Relay or switch replacement

Test or replace the turn signal relay/switch if wiring appears intact and fuse keeps blowing.

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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1873 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 B1873

What happens after you fix the fault

Once the fault is repaired, B1873 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.