B1978 OBD-II Trouble Code: Passenger’s Front Seat Down Switch Circuit Short to Battery

Our certified mechanics come to you · 12-month, 12,000-mile warranty

SCHEDULE B1978 DIAGNOSTIC Get a fair and transparent estimate upfront
Red-stars EXCELLENT RATING ON

Cost of diagnosing the B1978 code

B1978 is a diagnostic trouble code (DTC) for "Passenger’s Front Seat Down Switch Circuit Short to Battery". 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 B1978 DIAGNOSTIC Get a fair and transparent estimate upfront

B1978 code definition

The B1978 trouble code detects a circuit error from the passenger front seat down switch.

What the B1978 code means

The B1978 code is a standard OBD-II trouble code that signals a passenger front seat down switch circuit problem. The passenger front seat down switch is used to control the height of the passenger seat cushion front. When this switch is pressed, the front of the seat cushion is lowered, which adjusts the angle to help the passenger find comfort. This switch is usually placed on the outboard side of the front passenger seat. If a passenger front seat down switch circuit error is noted by the body control module or powertrain control module (PCM), then the B1978 trouble code may be detected.

What causes the B1978 code?

The B1978 trouble code is usually caused by one of two things. The first is damaged electrical components in either the passenger front seat down switch, or the power seat system. The second is a malfunctioning passenger front seat down switch. The B1978 code can also be triggered by a defective body control module, though this is very rare and should not be assumed unless all other potential causes have been ruled out.

What are the symptoms of the B1978 code?

The B1978 trouble code will likely keep the front of the passenger seat cushion from being adjusted downwards, and likely upwards as well. It is also fairly common for this code to be accompanied by an illuminated check engine soon warning light on the gauge cluster.

How does a mechanic diagnose the B1978 code?

The B1978 code will be diagnosed using a standard OBD-II trouble code scanner. A reputable technician will use the scanner to assess the code by looking at the freeze frame data. The scanner will also be used to see if there are any additional trouble codes detected. If there are, they should be assessed in the order that they are displayed in. The trouble codes should then be reset, the vehicle restarted, and the B1978 code searched for. If the code is no longer detected, then it was likely detected inaccurately, or is the result of an intermittent issue.

If the code is still present, then the mechanic will visually inspect all of the electrical parts in the passenger front seat down switch and power seat systems. Any shorted wires, blown fuses, or open or corroded connectors will need to be replaced. If the electrical system is in good working condition, then it the passenger front seat down switch has likely failed.

After any replacements or repairs are made, the trouble codes will again be reset, the vehicle restarted, and the B1978 code checked for. This allows the mechanic to know when the problem has been fixed.

Common mistakes when diagnosing the B1978 code

The most frequently made error when diagnosing the B1978 code comes from a failure to follow the OBD-II diagnosis protocol. It is very important that technicians always adhere to the diagnosis protocol, as it greatly increases the chances of accurate repairs.

It is fairly common for electrical failures to be overlooked, which often results in unnecessary passenger front seat down switch replacements.

How serious is the B1978 code?

A vehicle with a B1978 trouble code will not have any drivability problems. However, the front of the passenger seat cushion will likely not be able to adjust, which can cause comfort and practicality issues for the passenger. As is the case with all trouble codes, when the B1978 code is detected, an inspection should be scheduled.

What repairs can fix the B1978 code?

Possible repairs for the B1978 trouble code are:

Additional comments for consideration regarding the B1978 code

The B1978 trouble code is a manufacturer specific code, which means that the definition of the code changes from automaker to automaker. While this code commonly signals a passenger front seat down circuit error, it can detect a very different body problem in many other cars. It’s important for mechanics to be aware of what make and model they are inspecting before diagnosing the B1978 code.

Need help with a B1978 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
OBD-II
B1978

Fast and easy Check Engine Light is on Inspection service at your home or office.

SCHEDULE B1978 DIAGNOSTIC
Get a fair and transparent estimate upfront

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

4,743

Rating Summary
4,361
185
47
28
122
4,361
185
47
28
122

Oreste

12 years of experience
108 reviews
Oreste
12 years of experience
Nissan Altima - Check Engine Light is on - Hialeah, Florida
Showed up quick, and went straight to inspecting a brake light on the dash issue. He found the issue, fixed it, and showed me exactly what was wrong. Thank you!

Daniel

9 years of experience
58 reviews
Daniel
9 years of experience
Honda Fit - Check Engine Light is on - Chicago, Illinois
Told me everything I needed to know and switch out after the inspection. So, I scheduled another service the next day for all the fixes, or fluid maintenance.

Patrick

31 years of experience
1032 reviews
Patrick
31 years of experience
Hyundai Santa Fe - Check Engine Light is on - Austin, Texas
Even after working on my car, he took the time to explain what he did, the parts, and any next steps. Very knowledgeable!

Joe

12 years of experience
22 reviews
Joe
12 years of experience
Toyota 4Runner - Check Engine Light is on - Sacramento, California
Joe was very thorough in his inspections, and his knowledge & experience was clear in his explanations of what was wrong with my car. I really appreciated his recommendations, and the fact that he worked so efficiently that it cut down on time... I would definitely book with him again.

More related articles

P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222 code means The manufacturer specifies a range of...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost pressure sensor B input circuit range or performance...
How to Buy Fuel Treatments
Adding Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine, and increase gas mileage. When trying to decide on which additive...

Related questions

Check Engine Light is on and Autozone read: Trouble Code P0138 O2 Sensor Bank 1 Sensor 2 High Voltage

Hello. If it has a code for an oxygen sensor then that may be the issue. The thing about the oxygen sensors though is that they can give a false reading if there is something else going on with the...

2 major issues

The code P0453 is for the purge control valve; it's most likely bad and needs to be replaced. The ticking noise is possibly the oil pressure dropping too low at idle and the camshaft followers are getting noisy. Have the...

Car is reading trouble code PO136 01/01

Hi. There could be a couple of things going on here. There are multiple oxygen sensors on your car and sometimes what we think bank 1 is may not be and the wrong oxygen sensor is replaced giving us the...

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.

1-800-701-6230 · hi@yourmechanic.com