B1566

Door Ajar Circuit Short To Ground

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

In plain language — no jargon

The door ajar sensor circuit is shorted to ground, meaning the electrical signal wire is touching metal and draining away. Think of it like a water hose with a hole in it—the signal can't reach the ECU properly.

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Symptoms You May Notice

3 known symptoms for this code
Door ajar warning light stays on constantly
Interior dome light remains on when doors are closed
Door lock system malfunctions or won't engage
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors the door ajar sensor circuit voltage, expecting high signal when doors are closed and low signal when open. A short to ground causes the voltage to drop to zero unexpectedly, triggering the fault code.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Door Ajar Signal Voltage 5V (doors closed) / 0V (door open) 0V constantly (short to ground)
Circuit Resistance High impedance when closed Near 0 ohms (short condition)
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Door ajar switch/sensor
Replace the faulty door sensor that is internally shorted; this is the most common cause.
2
Wiring harness and connectors
Inspect the sensor wiring for cuts, damaged insulation, or corrosion and repair or replace damaged sections.
3
Door latch assembly
If the sensor is integrated into the latch, replace the entire door latch mechanism.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1566 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 B1566

What happens after you fix the fault

Once the fault is repaired, B1566 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.