B1939 – Air Bag Passenger Pressure Switch Circuit Short To Ground

The ODBII code B1939 indicates a malfunction in the airbag system, specifically that the passenger pressure switch circuit is shorted to ground, which may prevent the airbag from deploying properly in the event of a collision.

The severity of ODBII code B1939 is moderate to high.

Common Causes For: B1938 Air Bag Passenger Circuit Short To Ground

• Faulty passenger airbag pressure switch
• Damaged wiring or connectors in the circuit
• Short circuit in the wiring harness
• Corroded or poor electrical connections
• Faulty airbag control module
• Incorrectly installed or malfunctioning seat sensors
• Water intrusion or moisture in the electrical components

Common misdiagnosis for B1939 Air Bag Passenger Pressure Switch Circuit Short To Ground

• Faulty airbag control module
• Defective passenger airbag
• Wiring issues or shorts in the harness
• Faulty seat occupancy sensor
• Malfunctioning airbag connector
• Incorrectly installed or damaged seat
• Issues with the vehicle’s body control module
• Low battery voltage or electrical system problems
• Faulty diagnostic tool readings
• Software or calibration issues in the airbag system

Common Troubleshooting Steps

When dealing with an OBD-II code B1939, which indicates a problem with the airbag passenger pressure switch circuit shorted to ground, it’s important to follow a systematic approach to troubleshoot the issue. Here are common troubleshooting steps:

• Scan Tool Verification: Use an OBD-II scanner to confirm the presence of the B1939 code and check for any other related codes that may provide additional context.
• Visual Inspection: Inspect the wiring and connectors associated with the passenger pressure switch. Look for signs of damage, corrosion, or loose connections.
• Check the airbag module and related components for any physical damage.
• Check the Passenger Pressure Switch: Locate the passenger pressure switch (usually found in the seat or seat cushion).
• Test the switch for continuity using a multimeter. It should show continuity when the seat is occupied and no continuity when it is unoccupied.
• Inspect the Circuit: Use a wiring diagram to trace the circuit from the passenger pressure switch to the airbag control module.
• Check for any shorts to ground in the wiring. This can be done by measuring resistance between the circuit and ground.
• Test the Airbag Control Module: If the wiring and switch are intact, the issue may lie within the airbag control module itself. Check for any fault codes in the module and perform any necessary tests as per the manufacturer’s specifications.
• Check for Ground Issues: Ensure that the ground connections for the airbag system are secure and free of corrosion. A poor ground can cause false readings and trigger codes.
• Clear Codes and Test Drive: After performing repairs or adjustments, clear the codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the B1939 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues.
• Professional Diagnosis: If the issue persists after following the above steps, consider seeking help from a professional technician who specializes in automotive electrical systems and airbag diagnostics.Safety Note: – Always take precautions when working with airbag systems. Disconnect the battery and wait for a period (usually around 10-15 minutes) before working on airbag components to avoid accidental deployment. By following these steps, you should be able to identify and resolve the issue related to the B1939 code.