B1921 OBD-II Trouble Code: Air Bag Diagnostic Monitor Ground Circuit Open

Our certified mechanics come to you · Get a fair and transparent estimate upfront

Red-stars EXCELLENT RATING ON

Cost of diagnosing the B1921 code

B1921 is a diagnostic trouble code (DTC) for "Air Bag Diagnostic Monitor Ground Circuit Open". 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
SCHEDULE B1921 DIAGNOSTIC Get a fair and transparent estimate upfront

B1921 code definition

A B1921 trouble code indicates that the circuit relating to the airbag system's diagnostic monitor has been reported as incomplete, or "open."

What the B1921 code means

Because a successfully deployed airbag can mean the difference between life and death in crash situations, the airbag system comes with its own diagnostic module to keep track of potential airbag-related issues. In the case of a B1921 trouble code, the circuit associated with diagnosing issues has been identified by the vehicle's Engine Control Unit (ECU) as being broken and incomplete.

What causes the B1921 code?

The airbag's diagnostic module may be malfunctioning or otherwise faulty. Wiring, electrical connectors and other related electrical circuitry may also be to blame for this concern. In some rare instances, the ECU itself may be reporting the problem falsely. However, you should only consider causes beyond the airbag system once all other likelier causes have been exhausted.

What are the symptoms of the B1921 code?

If the airbag system's diagnostic module isn't working properly, a B1921 code will likely result in being unable to identify and diagnose other airbag-related codes until the diagnostic module's issue has been properly addressed. As such, you should safely assume in a B1921 instance that the airbag system is unreliable. In addition, for the purpose of diagnosing the issue, the vehicle's onboard computer will log a B1921 code and the dashboard trouble light will be illuminated. These symptoms can be ignored once the specific issue has been identified.

How does a mechanic diagnose the B1921 code?

A mechanic may first diagnose a B1921 issue by reading the code via a OBD-II code scanner. Check any fuses (such as the thermal fuse) related to the airbag's diagnostic monitor and repair them if they've been blown or otherwise cited as faulty. Any wiring related to the diagnostic monitor ground circuit should be tested for signs of fault, including damage, disconnection and/or corrosion.

Common mistakes when diagnosing the B1921 code

Trouble codes beginning with the letter B (Body-related trouble codes) may describe different issues depending on the particular make and model of vehicle in question. Make sure the code is describing the specific issue before moving forward with repairs. Your OBD-II code reader may specify the description for you after scanning. Refer to the vehicle's user manual or contact the manufacturer if you're uncertain.

How serious is the B1921 code?

The potential severity of a B1921 trouble code will depend based on the likelihood of other airbag-related problems currently in the vehicle. Without the diagnostic module working properly, you may not be able to know the extent of other issues relating to the airbag. Because of this, in the case of a B1921 code you should consider the airbag system unreliable.

What repairs can fix the B1921 code?

The airbag's diagnostic module should be taken out, then repaired or replaced as needed. Any disconnected, corroded, broken or damaged wiring should be repaired or replaced accordingly. Following any repairs made to address the B1921 code, the vehicle should be restarted and tested. If the ECU has been cited as faulty, it should be reprogrammed or replaced accordingly. Giving the code time to recur will allow you to verify whether or not the code has been solved.

Additional comments for consideration regarding the B1921 code

Make sure the ignition has been turned off for at least five minutes before moving on to repair anything associated with the airbag system. Accidentally triggering the airbag during repair can result in severe injury or death.

Need help with a B1921 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.

B1921
trouble codes
OBD-II

No more waiting rooms! Our mechanics will come to you to diagnose and fix the B1921 code.

SCHEDULE B1921 DIAGNOSTIC
Get a $20 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating

(6,114)

Rating Summary
5,655
221
51
35
152
5,655
221
51
35
152

Kevin

24 years of experience
388 reviews
Kevin
24 years of experience
Chevrolet Tracker - Check Engine Light is on - Stone Mountain, Georgia
Kevin was pretty cool! He explained things to me in a way I could understand and was able to offer me some good options to fix my car problems! Very professional and knew his stuff! Excellent experience

JOHNNY

33 years of experience
63 reviews
JOHNNY
33 years of experience
Toyota Camry - Check Engine Light is on - Carmichael, California
Johnny was early, friendly, and thorough! He explained things to me about my car that I had no idea about before! I booked him for a diagnostic appointment and I’m definitely requesting him for a follow-up!

Benji

22 years of experience
184 reviews
Benji
22 years of experience
Jaguar XK - Check Engine Light is on - Phoenix, Arizona
Will absolutely recommend Benjie to all my friends, thorough and knowledgeable. Will have him back fit all future car repairs!

Marco

29 years of experience
124 reviews
Marco
29 years of experience
Kia Soul - Check Engine Light is on - Riverside, California
Marco was great. Cam on time, and explained everything he did. Also gave good recommendation for fixing as the problem has a Kia recall.


More related articles

P0989 OBD-II Trouble Code: Transmission Fluid Pressure Sensor/Switch E Circuit Low
P0989 means there is an issue with the E circuit in the transmission fluid pressure sensor, likely due to a bad sensor, solenoid, or fluid level.
P0515 OBD-II Trouble Code: Battery Temperature Sensor Circuit
P0515 trouble code means there is an issue with the battery temperature sensor circuit often caused by battery corrosion or engine overheating.
B1951 OBD-II Trouble Code: Seat Rear Up/Down Potentiometer Feedback Circuit Open
B1951 means there is an incomplete or open circuit in the rear seat's potentiometer, possibly due to defective electrical components.

Related questions

How long and what is the process to replace a fuel pressure sensor?

A professional mechanic would require roughly 5 hours. (If just the regulator is replaced that takes about 1 hour). Some parts, as noted below, cannot be re-used, you need a precision inch pound torque wrench, FSM instructions (and TSB updates...

Check Engine Light is on, trouble code P0011&12. I changed the oil and filter. I need to turn off the engine light to see if that problem is solved.

Hello. If the oil level was low or if the wrong oil war previously used then that can cause these codes to come up. Most of the time though, on this engine, it is caused by a failure in the...

My car is a Nissan Navara. My Check Engine Light is on and my acceleration is not well.

Hi there. It seems that the engine you have is a diesel engine. The code P2002 is coming up for the particulate filter and it has an efficiency issue. The only thing to do with this is replace the particulate...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com