B1901

Air Bag Crash Sensor #1 Feed/Return Circuit Short To Ground

Body Chassis/Safety Airbag/SRS 🟢 Low — Fix at next service ✅ Safe to Drive
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What This Actually Means

In plain language — no jargon

The airbag crash sensor's wiring is shorted to ground, preventing the system from detecting a collision properly. Think of it like a light switch that's stuck in the "off" position due to a broken wire touching the metal frame.

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Symptoms You May Notice

3 known symptoms for this code
Airbag warning light illuminated on dashboard
Airbags may not deploy in a collision
SRS system inactive or disabled
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The SRS module monitors the voltage and resistance of the crash sensor feed/return circuit. It expects a specific resistance range when the sensor is inactive. A short to ground drops the voltage to near 0V and resistance to nearly 0 ohms, triggering the fault.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Circuit Resistance 300-600 ohms < 50 ohms (shorted to ground)
Circuit Voltage 4.5-5.5V < 0.5V
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Wiring harness/connector inspection
Visually inspect the crash sensor wiring harness for damaged insulation, pinched wires, or loose connectors near the sensor location.
2
Crash sensor connector
Disconnect and reconnect the crash sensor connector firmly; clean any corrosion with electrical contact cleaner.
3
Crash sensor assembly
Replace the crash sensor if wiring is confirmed damaged or connector cleaning does not resolve the fault.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1901 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 B1901

What happens after you fix the fault

Once the fault is repaired, B1901 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.