B2105 code definition
The B2105 trouble code detects a throttle position input range error.
What the B2105 code means
The B2105 code is a generic OBD-II trouble code that detects a throttle position input range problem, as it pertains to the four-wheel drive (4WD) system. The throttle position sensor is responsible for detecting the position of the throttle pedal, and relaying that information to the powertrain control module (PCM), which uses the data to control the proper fuel and air mixture. In vehicles with 4WD, the PCM relays this throttle information to the 4WD control module, which uses the information to help control the 4WD clutch. If the 4WD control module is unable to receive this reading from the PCM, then the B2105 trouble code may be stored.
What causes the B2105 code?
The most likely cause of the B2105 trouble code is a damaged circuit in the 4WD system. Loose harnesses, short circuits, and blown fuses can all trigger this code. It is also fairly common for the code to be stored due to loose connectors in the 4WD control module. In rare cases, the code may also be the result of a failed 4WD control module or PCM.
In addition to these causes, the B2105 trouble code can be caused by throttle position sensor failures, such as a malfunctioning or misadjusted throttle pedal position sensor, damaged electrical components in the throttle position sensor system, or a defective throttle body. If this is the case, this code will be accompanied by throttle position powertrain trouble codes, and those codes will likely need to be diagnosed first.
What are the symptoms of the B2105 code?
When the B2105 trouble code is detected, the 4WD system will likely not function properly, as the 4WD clutch will not have the information it needs to operate correctly. The vehicle may experience more slip than is usually associated with a 4WD vehicle, and may have a difficult or impossible time shifting into or out of 4WD. The code will likely be accompanied by an illuminated check engine soon Warning Light and a 4WD Warning Light on the gauge cluster.
If the vehicle also has present throttle position powertrain trouble codes, then there likely will be throttle problems that may include constant stalling, poor acceleration, black exhaust when the vehicle is turned on, or an inability to start.
How does a mechanic diagnose the B2105 code?
The B2105 code will be diagnosed using a standard OBD-II trouble code scanner. A reputable mechanic will use the scanner to view the freeze frame data and assess the code, while also checking to see if there are any other codes present. If numerous trouble codes are detected, then the mechanic will need to address them in the order that the scanner displays them in. The trouble codes should then be reset, the vehicle restarted, and the B2105 code checked for. If the code is no longer detected, then it was likely erroneously detected, or is the fault of an intermittent issue.
If the code remains detected, and is preceded by throttle position sensor powertrain trouble codes, then the issue will likely be resolved by following the diagnosis protocol for those codes. If the code is not accompanied by such codes, then the mechanic will inspect all of the electrical components in the 4WD system, test the circuits, and replace any parts that are not working properly. The 4WD control module should then be disconnected so that the connectors can be checked and tested.
After any components are repaired or replaced, the mechanic will reset the trouble codes, restart the vehicle, and check again for the B2105 code. By doing this, the technician will know as soon as the issue is resolved.
Common mistakes when diagnosing the B2105 code
The most commonly made error when diagnosing this code comes from a failure to properly abide by the OBD-II diagnosis protocol. Mechanics should always observe the protocol, to help ensure accurate and efficient diagnoses.
Often functional 4WD control modules are replaced because the circuits were not properly checked.
How serious is the B2105 code?
The B2105 trouble code will likely present noticeable drivability problems. The vehicle may not be able to shift into or out of 4WD, and, more dangerously, will likely experience more slippage than normal due to an ineffective 4WD clutch. When the B2105 code is detected, an inspection and repair should be scheduled for as soon as possible.
What repairs can fix the B2105 code?
Repairs for the B2105 trouble code are:
- Replacement of circuits in the 4WD system
- Repair of the 4WD control module connectors
- Replacement of the throttle position sensor
- Replacement of the throttle body
- Replacement of electrical components in the throttle position sensor
- In rare cases, replacement of the 4WD control module or the PCM
Additional comments for consideration regarding the B2105 code
The B2105 code only applies to vehicles with 4WD systems, and is a manufacturer specific trouble code, which means that the definition varies depending on the automaker. The B2105 code represents a throttle position input range issue in many cars, but signals a different error in many other vehicles. The technician should always be aware of what vehicle is being worked on when inspecting this code.
Need help with a B2105 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.
This article originally appeared on YourMechanic.com as B2105 OBD-II Trouble Code: Throttle Position Input Out of Range Low and was authored by Brady Klopfer.