B1903 code definition
The B1903 trouble code detects a circuit issue in the #1 airbag crash sensor.
What the B1903 code means
The B1903 code is a basic OBD-II trouble code that notes a #1 airbag crash sensor circuit malfunction. The crash sensors are responsible for detecting when a vehicle is in a collision, which triggers the airbags to be deployed. Different vehicles have different numbers of crash sensors, and different arrangements, so the placement of the #1 sensor varies depending on the car. If an abnormal voltage reading from the #1 airbag crash sensor circuit is detected by the airbag control module, powertrain control module (PCM), or body control module, then the B1903 trouble code may be detected.
What causes the B1903 code?
The B1903 code is commonly caused by two culprits. The first is damaged electrical components, such as wires, fuses, connectors, and the crash sensor circuit itself. The second common cause is a malfunctioning #1 airbag crash sensor. While very rare, the B1903 code can also be triggered as the result of a defective body control module, airbag control module, or PCM.
What are the symptoms of the B1903 code?
The B1903 trouble code will likely result in an illuminated check engine soon warning light on the instrument panel, and very often an illuminated airbag warning light. It is also likely that the airbag system will not function properly, and the airbags will not deploy in the event that an accident occurs.
How does a mechanic diagnose the B1903 code?
The B1903 code will be diagnosed using a generic OBD-II trouble code scanner. A reputable mechanic can use the scanner to view the freeze frame data and gather information about the code. The technician will also use the scanner to see if any additional trouble codes are present. If there are multiple trouble codes detected, then they should be diagnosed in the order in which they appear. The mechanic will then reset the codes, restart the vehicle, and see if the B1903 code remains detected. If the code disappears, then a faulty detection, or an intermittent error should be suspected.
If the code is still detected after the reset, then all of the electrical components in the airbag and crash sensor system should be visually inspected, and any damaged fuses, wires, or connectors will need to be replaced. The mechanic will then test the crash sensor circuit, and then the #1 airbag crash sensor.
Any time the mechanic replaces a component, the trouble codes will need to again be reset, the vehicle restarted, and the B1903 code looked for. By doing this, the technician will be alerted when the problem has been resolved.
Common mistakes when diagnosing the B1903 code
The most commonly made mistake when diagnosing this code is the failure to properly follow the OBD-II diagnosis protocol step by step. Mechanics should always adhere to the diagnosis protocol, to make sure that inspections and repairs are accurate and efficient. It is fairly common for fully operational airbag crash sensors to be unnecessarily replaced, because the electrical components in the system were not inspected first.
How serious is the B1903 code?
A vehicle with the B1903 trouble code detected will not experience any drivability problems, but the airbags will probably fail to deploy if the car is in a crash. Airbags are a critical safety feature that limit driver and passenger damage, and often save lives. Because of this, the car should not be driven until it has been inspected and repaired.
What repairs can fix the B1903 code?
Repairs for the B1903 code include:
- Replacement of fuses, wires, and connectors
- Replacement of the #1 airbag crash sensor circuit
- Replacement of the crash sensor
- In rare cases, replacement of the PCM, body control module, or airbag control module
Additional comments for consideration regarding the B1903 code
The B1903 code is a manufacturer specific trouble code. This means that the code has different definitions depending on the automaker, and thus does not always signal a problem with the #1 airbag crash sensor circuit. It is important that technicians always take into account the car they are working on when diagnosing the B1903 trouble code.
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