Airbag Light | BMW E46

🚗 2000 BMW 328 (E46)

• Came in with an airbag light on
• DTC in Multiple Restraint System (MRS)
  • 20 left side airbag sensor line fault

🩺 Diagnosis

There are only 3 possible causes for this code

• Left Side Impact Sensor
• Wiring
• MRS (airbag) Module

Left Side Airbag Sensor is located under carpet under driver front seat.

Wiring Check

• Check for power at pin 3 and ground at pin 1 of the left side impact sensor (S71).
  • If there is no ground at pin 1, check X46 ground under the center console.
    • 
  • If there is no power at pin 3, test for continuity from left side impact sensor pin 3 to pin 20 at SRS module (A12).

In my case, wiring was good, but the sensor was corroded from the water intrusion.

Replaced the sensor and all is well.