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B1909 OBD-II Trouble Code: Air Bag Crash Sensor #2 Ground Circuit Short to Ground

diagnostic check engine light

B1909 code definition

The B1909 trouble code detects a #2 airbag crash sensor circuit malfunction.

What the B1909 code means

The B1909 code is a generic OBD-II trouble code that notes an error with the #2 airbag crash sensor circuit. Crash sensors are used to determine when the vehicle is experiencing extreme impact, so that the airbags can deploy. Different vehicles rely on different numbers of crash sensors, and different placement as well, so the location of the #2 sensor can vary depending on the make and model of the car. If the airbag control module, body control module, or powertrain control module (PCM) notice an abnormal voltage reading from the #2 airbag crash sensor circuit, then the B1909 code could be stored.

What causes the B1909 code?

There are two common issues that can cause the B1909 trouble code to be stored. The first is damaged electrical components, such as the wires, connectors, and fuses in the airbag crash sensor system, or even the circuit itself. The second common cause is a faulty #2 airbag crash sensor. The B1909 code may also be caused by a malfunctioning airbag control module, body control module, or PCM, but this is highly uncommon.

What are the symptoms of the B1909 code?

When the B1909 code is detected, the check engine soon warning light will likely illuminate on the gauge cluster, as will the airbag warning light. Most importantly, the airbag system is unlikely to work, which means that there will be no airbag protection should the vehicle be involved in an accident.

How does a mechanic diagnose the B1909 code?

The B1909 code will be diagnosed with an OBD-II trouble code scanner. A trained technician will use the scanner to view the freeze frame data and gather information about the code, while also checking for the presence of other trouble codes. If numerous codes are stored, then they will need to be inspected in the order that the scanner displays them in. The trouble codes will then be reset, the vehicle restarted, and the B1909 code again checked for. If the code is not detected after this reset, then it was probably triggered incorrectly, or is the result of an intermittent issue.

If the B1909 code remains detected, then the mechanic will visually inspect the electrical components in the airbag crash sensor system. Any blown fuses, open or corroded connectors, or shorted wires will need to be replaced. The circuit will then need to be tested, followed by an inspection of the #2 airbag crash sensor.

After any parts are replaced, the trouble codes should again be reset, the vehicle restarted, and the B1909 code checked for. By doing this, the technician will be alerted as soon as the issue is resolved.

Common mistakes when diagnosing the B1909 code

The most frequently made mistake when diagnosing this code comes from not properly abiding by the OBD-II diagnosis protocol. It is very important that mechanics comply with the protocol step by step, to help eliminate the risk of improper diagnoses and repairs.

Fully operational #2 airbag crash sensors are commonly replaced when damaged electrical components are not noticed.

How serious is the B1909 code?

A vehicle with the B1909 code will not experience any drivability issues. The airbag system will likely be inoperable though, which means that the driver and passengers may not be protected by the airbags should an accident occur. Airbags are vital safety features that often safe lives, so the vehicle should not be driven until an inspection has been performed.

What repairs can fix the B1909 code?

Repairs for the B1909 trouble code include:

  • Replacement of the #2 airbag crash sensor circuit
  • Replacement of the #2 airbag crash sensor
  • Replacement of fuses, wires, or connectors
  • In very rare cases, replacement of the PCM, airbag control module, or body control module

Additional comments for consideration regarding the B1909 code

The B1909 code is a manufacturer specific trouble code. Manufacturer specific codes have varying definitions depending on the automaker, so the B1909 code may detect a completely different issue in other cars. Any technician that is diagnosing this code should take into account the vehicle that they are working on before beginning their inspection.

Need help with a B1909 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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