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B1984 OBD-II Trouble Code: Seat Switch Lumbar Inflate Circuit Failure

diagnostic check engine light

B1984 code definition

A B1984 trouble code indicates that the vehicle's Engine Control Unit (ECU) has detected an unspecified failure regarding the seat switch's lumbar inflate circuit.

What the B1984 code means

The lumbar circuits are so-named for relating to the lower region of the back. Certain luxury models of car will come equipped with these adjustable cushions which, when controlled, can help you sculpt the seat to suit your back. If a B1984 trouble code has been reported, the lumbar inflate circuit has suffered an unspecified failure. This will likely restrict the ability to inflate the cushion.

What causes the B1984 code?

Faulty components and electrical circuitry are most often to blame for an unspecified circuit failure. Some cases of the B1984 trouble code may be reported falsely by a malfunctioning ECU. Although this is a much rarer scenario than a failed circuit, it may be considered if all other plausible explanations have been exhausted.

What are the symptoms of the B1984 code?

A B1984 will restrict the lumbar control's ability to inflate (or harden) the lumbar cushion. In addition, the B1984 trouble code will come along with a stored trouble code and illuminated check engine lamp on the dashboard. These symptoms are diagnostic in nature, and are used to identify the issue in the first place.

How does a mechanic diagnose the B1984 code?

A mechanic may first diagnose the B1984 trouble code by reading the ECU with an OBD-II code scanner. The lumbar circuit may be found underneath the seat in question. From there, the lumbar circuit should be thoroughly inspected, checking for any apparent stops or damages relating to the electrical wiring or connectors. If all of the lumbar circuitry checks out, inspect the ECU for potential signs of malfunction.

Common mistakes when diagnosing the B1984 code

A B1984 is a body-related trouble codes. B-class codes can pose a risk of misinterpretation for home repairs, as one code can stand for different issues depending on the make and model of vehicle. Your OBD-II code reader may specify the issue for you. If you're not sure of the description, refer to the user manual or contact the manufacturer. Going through with repairs to an unrelated problem can be a major nuisance and risk wasted investment. All the while, the real problem will remain unaddressed.

How serious is the B1984 code?

Because of the pure luxury factor of a lumbar cushion, a B1984 trouble code shouldn't be seen as a serious problem, and can be repaired purely at the owner's discretion. Although no lumbar-related codes should be seen as serious concerns, the B1984 is slightly less serious than its B1985 ("cannot deflate lumbar") counterpart. This is because a highly inflated lumbar may prove more uncomfortable to a driver than a deflated cushion.

What repairs can fix the B1984 code?

If you have noted any wiring as being faulty, damaged, disconnected or otherwise problematic, it should be replaced, repaired, or rewired accordingly. In the event ECU has been proven faulty, it will need to be reprogrammed or replaced. Upon completing your repairs for the B1984 code, restart the vehicle to see if the code recurs. If the code returns upon restarting, you should return to the diagnostic phase of repair and see if you missed anything the first time around.

Additional comments for consideration regarding the B1984 code

You can purchase an independent lumbar cushion if you'd like to retain the lumbar support without making the repairs.

Need help with a B1984 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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