OBD Code B1573: Door Ajar LR Circuit Short To Battery

Q: What does OBD code B1573 mean?

Door Ajar LR Circuit Short To Battery. The left rear door's ajar sensor is sending a constant 'high' signal to the ECU, like a switch stuck in the pressed position. This prevents the system from accurately detecting whether the door is actually open or closed.

Q: What are the symptoms of fault code B1573?

Door ajar warning light stays on continuously, Interior lights remain on even with door closed, Power windows or locks may not function properly

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What This Actually Means

In plain language — no jargon

The left rear door's ajar sensor is sending a constant 'high' signal to the ECU, like a switch stuck in the pressed position. This prevents the system from accurately detecting whether the door is actually open or closed.

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Symptoms You May Notice

3 known symptoms for this code

Door ajar warning light stays on continuously

Interior lights remain on even with door closed

Power windows or locks may not function properly

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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors the door ajar switch circuit voltage. It expects a low voltage (~0V) when the door is closed and high voltage (~12V) when open. A short to battery keeps the voltage pinned high regardless of actual door position, triggering the fault.

Voltage & Parameter Thresholds

Parameter	Normal Range	Fault Condition
Door switch voltage	0V (closed) to 12V (open) transition	Constant 12V (shorted to battery)
Circuit resistance	Open circuit when closed (~infinite ohms)	Low resistance path to 12V source

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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

Door ajar switch connector

Inspect the LR door switch connector for corrosion, moisture, or loose pins and clean or reseat as needed.

2

Door ajar switch wiring harness

Check the wiring harness near the left rear door for pinched, damaged, or exposed wires contacting the door frame.

3

Door ajar switch assembly

Replace the faulty left rear door ajar switch if connector and wiring are intact.

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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1573 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 B1573

What happens after you fix the fault

Once the fault is repaired, B1573 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.