B1549

Power Window Master Circuit Short To Battery

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

In plain language — no jargon

The power window master switch circuit is shorted directly to battery voltage, causing the control module to detect excessive electrical current. It's like a light switch that's stuck in the 'on' position, continuously draining power and preventing normal operation.

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Symptoms You May Notice

3 known symptoms for this code
Power windows inoperative or stuck in one position
Electrical burning smell or visible damage near door panel
Battery drains rapidly or warning lights on dashboard
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The BCM monitors the power window master switch circuit voltage and current draw. When the circuit shorts to battery (12V+), the module detects voltage above normal threshold and unusually high current flow, triggering the fault code.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Circuit Voltage 0-5V (switch dependent) >10V sustained short to battery
Current Draw <500mA at rest >2A continuous draw
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Wiring harness inspection
Check for pinched, melted, or damaged wires near the door latch and window motor area.
2
Power window master switch
Replace the switch assembly if internal contacts are shorted or corroded.
3
Door panel connectors
Inspect and clean battery voltage supply connectors for corrosion or loose pins.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1549 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 B1549

What happens after you fix the fault

Once the fault is repaired, B1549 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.