B1939 OBD-II Trouble Code: Air Bag Passenger Pressure Switch Circuit Short to Ground

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Cost of diagnosing the B1939 code

B1939 is a diagnostic trouble code (DTC) for "Air Bag Passenger Pressure Switch Circuit Short to Ground". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
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B1939 code definition

The B1939 code is manufacturer-specific body code related to air bags. In this case, it means that the engine control module (ECM) has detected a fault with the passenger-side air bag pressure switch.

What the B1939 code means

A code B1939 will be stored when the ECM has detected a short to ground from the passenger-side air bag pressure switch.

What causes the B1939 code?

Several problems may cause a B1939 code including:

  • Damaged or corroded electrical wiring and related components
  • Damaged or defective passenger-side air bag pressure switch
  • Passenger-side air bag module malfunction
  • SAS control module malfunction

What are the symptoms of the B1939 code?

Symptoms of a B1939 code may include:

  • Check engine light may illuminate
  • Air bag light may incorrectly illuminate
  • Air bag light may flash
  • Passenger-side air bags may not inflate
  • There may be no symptoms other than a stored B1939 code

How does a mechanic diagnose the B1939 code?

A mechanic may use several methods to diagnose a B1939 trouble code, including:

  • Utilize an OBD-II scanner to check for a stored B1939 trouble code
  • Visually inspect wiring and related electrical components for signs of damage, wear, or corrosion
  • Inspect the passenger-side air bag module connector
  • Inspect the passenger-side air bag pressure switch
  • Inspect the wiring harness between the SAS control module and clock spring for short to the power supply
  • Inspect passenger-side air bag module
  • Perform SAS control module DTC inspection

Common mistakes when diagnosing the B1939 code

Due to the danger involved with repairing most items related to a vehicle’s air bag system, it is recommended to seek assistance from a professional for repair. If performing repairs yourself, be sure to follow all possible safety precautions and procedures.

How serious is the B1939 code?

Because a vehicle’s safe driving operation can be impacted due to faults that store a B1939 code, this code is considered a potentially serious code. When this code appears, it is recommended to immediately take your vehicle to your local service center or mechanic for repair and diagnosis.

What repairs can fix the B1939 code?

Several repairs can fix a B1939 trouble code and include:

It cannot be stressed enough that improperly handling a vehicle’s air bag system components can accidentally deploy the air bag modules and pre-tensioner seat belts, which can seriously injure you and others in the vicinity. Read all service warnings and cautions before handling air bag system components. Anything related to air bag repairs can be both difficult and dangerous, and is often best left to professionals for diagnosis and repair. If making any repairs at home, take care with the air bags when removed from the vehicle.

Need help with a B1939 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.

trouble codes
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B1939

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Anthony

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6 years of experience
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Anthony was great! We are very happy that we chose to go with this company instead of the overpriced and slow service we get from the Jeep dealership. He was on time and did the job just as expected. He identified a couple of other things that need to be done before the problems get worse. We appreciate having a technician give us direct feedback regarding our vehicle, rather than a service advisor (salesperson) that we've had to deal with in the past at the dealership. We'll be booking the addtional services very soon and will definitely request Anthony again now that he is familiar with our vehicle!

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37 years of experience
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37 years of experience
Subaru Forester - Check Engine Light is on - Santa Fe Springs, California
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6 years of experience
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Anthony
6 years of experience
BMW 740Li - Check Engine Light is on - Roseville, California
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