Technical Description of OBD-II Trouble Code
Signal for Decreasing Cruise Control Distance
What does that signify?
This is a generic diagnostic trouble code (DTC) for powertrain issues and is commonly found in OBD-II vehicles with cruise control. This can include vehicles from various manufacturers such as Peugeot, Ford, Nissan, Chevrolet, Hyundai, VW, Audi, Citroen, and others. While the code is generic, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
Cruise control systems in vehicles offer various functions. In addition to setting a specific speed that can be automatically maintained using sensors, switches, modules, and other components, the speed can also be electronically modified (e.g. “set -” and “resume +”) and temporarily adjusted for passing vehicles or unexpected stopping/slowing.
Since most of the functions mentioned in the description of code P056B and related codes (P0565, P0566, P0567, P0568, P0570, etc.) are contained within a single switch/component, it should be relatively easy to locate the mechanical inputs (e.g. buttons, switches, talks) involved. Some common names for this component(s) include Multi-function switch, Steering wheel controls, Cruise control switch, Cruise control module, and Accessory switch.
In the case of this code, the Engine Control Module (ECM) has detected a malfunction in the signal circuit. In simple terms, there was an issue within the circuit related to the mentioned function.
When the ECM detects a signal malfunction in one or more of the cruise control functions, it illuminates the Check Engine Light (CEL) with code P056B and/or related codes. The use of the affected function will most likely be disabled or behave abnormally.
Code P056B is set when the ECM detects a malfunction in the DECREASE DISTANCE signal of the adaptive cruise control (ACC) system.
NOTE: ACC systems are complex in design and require special tools and diagnostic procedures to properly address any faults.
An example of cruise control buttons on a steering wheel:
What is the severity of this DTC?
The severity of this DTC is considered moderately low. Even if the entire cruise control system loses functionality, it is still possible to safely drive the vehicle. However, neglecting any electrical issue for an extended period of time may lead to further damage.
What are some of the symptoms of the code?
Symptoms of a P056B trouble code may include:
What are some of the common causes of the code?
Some possible causes of the P056B code include:
What are some P056B troubleshooting steps?
Basic Step #1
Start by visually inspecting the cruise control switch/module. Check for missing buttons, buttons stuck due to cola or other substances, loose buttons that do not make proper electrical connections, and any contamination that could potentially damage the buttons. Also, make a note of all malfunctions or abnormalities in the cruise control functions.
Basic Step #2
Check if the cruise control light in the instrument cluster comes on when the cruise control is manually activated. If not, verify if there is a fuse for the circuit and replace any blown fuses with new ones approved by the manufacturer. Refer to the vehicle’s service manual for fuse information.
Basic Step #3
To access the harness to the cruise control switch/module, you will likely need to remove certain dash parts such as the steering column shroud and airbag module in the steering wheel. To identify the specific wire involved in the fault, you will need a proper wiring harness for your vehicle. These harnesses can vary significantly, so always consult the appropriate service information before performing invasive actions.
Basic Step #4
Ensure that your Anti-lock Braking System (ABS) is in good working order and that there are no ABS lights illuminated on the dashboard. The ABS system uses various sensors, including speed sensors, which, if malfunctioning, could cause the vehicle’s computers to incorrectly perceive the speed.
