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B1977 OBD-II Trouble Code: Passenger’s Front Seat Up Switch Circuit Short to Battery

diagnostic check engine light

B1977 code definition

The B1977 trouble code notes a passenger front seat up switch circuit malfunction.

What the B1977 code means

The B1977 code is a generic OBD-II trouble code that detects a passenger front seat up switch circuit error. The front seat up switch is usually located on the outboard side of the front passenger seat, and is used to adjust the height of the front of the seat. When the switch is deployed, the front of the seat will move upwards, to alter the angle to the passenger’s liking. If the body control module or powertrain control module (PCM) ever notices a circuit issue from the passenger front seat up switch, then the B1977 code may be stored.

What causes the B1977 code?

There are two problems that commonly cause the B1977 trouble code to be detected. The first common cause is damaged wires, connectors, or fuses, either in the passenger front seat up switch, or in the power seat system itself. The second common cause is a defective passenger front seat up switch. This code can also be caused by a failed body control module, though this is a very rare occurrence.

What are the symptoms of the B1977 code?

When a vehicle has a stored B1977 trouble code, the height of the passenger seat front will likely not be able to be adjusted upwards (it will probably not be adjustable downwards either). It is also common for the check engine soon warning light to illuminate on the vehicle’s instrument panel.

How does a mechanic diagnose the B1977 code?

The B1977 code will be diagnosed with the help of a standard OBD-II trouble code scanner. A trained mechanic will use the scanner to look at the freeze frame data and gather information about the code, while also looking to see if any additional trouble codes are present. If the technician notices numerous trouble codes, then they will need to be diagnosed in the order that they appear in. The trouble codes should then be reset, the vehicle restarted, and the B1977 code checked for. If the code is no longer present following the reset, then it was most likely erroneously stored, or the result of an intermittent error.

If the code remains detected, then a visual inspection of all of the electrical components in the system should be performed. Any and all blown fuses, open connectors, or shorted wires will need to be replaced. If all of the electrical components are functional and in good shape, then the passenger front seat up switch is probably broken.

Any time the mechanic repairs or replaces a part, the trouble codes will again be reset, the vehicle again restarted, and the B1977 code checked for. This will allow the technician to know as soon as the issue is resolved.

Common mistakes when diagnosing the B1977 code

The most commonly made error when diagnosing the B1977 code comes from not following the OBD-II trouble code diagnosis protocol. Mechanics should follow the protocol step by step at all times, to help ensure thorough and accurate inspections.

Passenger front seat up switches are often inaccurately replaced because the electrical components were not first inspected.

How serious is the B1977 code?

A vehicle with a stored B1977 trouble code will be completely drivable, and will have no drivability concerns. The front part of the passenger seat cushion will most likely not be able to be vertically adjusted, which can be impractical or uncomfortable for the passenger. As with all trouble codes, an inspection should be scheduled when the B1977 code is detected.

What repairs can fix the B1977 code?

Repairs for the B1977 trouble code are:

Additional comments for consideration regarding the B1977 code

The B1977 trouble code is a manufacturer specific code. Manufacturer specific codes are codes that have varying definitions depending on the automaker. The B1977 code detects a passenger front seat up switch circuit error in some cars, but an entirely different body problem in other cars. Technicians should always be conscious of what vehicle they are working on when diagnosing this code.

Need help with a B1977 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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