B1574

Door Ajar LR Circuit Short To Ground

Body Chassis/Safety Door Position Sensing 🟢 Low — Fix at next service ✅ Safe to Drive
💬

What This Actually Means

In plain language — no jargon

The left rear door's electrical circuit is shorted to ground, preventing the door sensor from sending proper signals to the vehicle's control module. Think of it like a short circuit in a light switch—the current takes a shortcut to ground instead of flowing through the sensor properly.

⚡

Symptoms You May Notice

3 known symptoms for this code
Door ajar warning light stays on constantly
Interior dome light remains on even when doors are closed
Door lock system malfunctions or behaves erratically
🔬

How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors the door ajar switch circuit voltage on the left rear door. The circuit should float high (5V) when the door is closed and pull to ground when open. A short to ground forces the voltage to 0V continuously, signaling a fault condition regardless of actual door position.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Door Ajar Circuit Voltage 5V (closed) / 0V (open) 0V continuously or voltage cannot rise above 0.5V
Circuit Resistance to Ground >10 kΩ when closed <100 Ω indicating direct short
🔧

Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Door ajar switch connector
Inspect and reseat the left rear door switch connector at the door latch for corrosion or loose pins.
2
Door ajar switch wiring harness
Check the wiring harness between the door and body for damage, pinches, or exposed conductors causing a short.
3
Door ajar switch assembly
Replace the left rear door switch if connector and wiring are intact but continuity tests confirm an internal short.
⚠️

When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1574 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.
🔄

How to Clear Code B1574

What happens after you fix the fault

Once the fault is repaired, B1574 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.