What does it mean?
SPECIAL NOTES: Since code P0581 involves the cruise control system, non-professional mechanics are strongly urged to read the section in the manual for the application being worked on that describes the cruise control system very carefully, before attempting a diagnosis/repair of this code.
Failure to gain at least a basic understanding of the cruise control system on the affected application will almost certainly result in misdiagnoses, damage to the application’s electrical system, the deployment of the airbag(s) in the steering wheel, and the unnecessary replacement of parts and components.
Non-professional mechanics should also note that due to significant design differences between the cruise controls systems fitted to different applications, this guide cannot provide detailed diagnostic and repair information that will be valid for all applications under all conditions. However, the generic information provided here should enable most non-professional mechanics to diagnose and repair the most common causes of code P0581 on most applications.
Also, be aware that diagnosing some causes of this code may require the use of professional grade diagnostic equipment, or the use of special tools/equipment that may only be available to dealers. In these cases, non-professional mechanics are strongly urged to refer the vehicle to a dealer or other competent repair shop for professional diagnosis and repair.
Always bear in mind that cruise control is a safety critical system and half-baked or sloppy diagnostic/repair procedures can render the system dangerous. Cruise control systems essentially assume control of a vehicle’s speed, and many fatal crashes have occurred as the direct result of sloppy repairs to cruise control systems that prevented a driver from deactivating the system.
Therefore, non-professional mechanics that are not comfortable with working on a safety-critical system are strongly urged to refer the vehicle for professional diagnosis and repair. END OF SPECIAL NOTES. OBD II fault code P0581 is a generic code that is most commonly defined as “Cruise control system, multi -function switch input “A” circuit high”, and is set when the PCM (Powertrain Control Module) detects an abnormally high input voltage from the cruise control multifunction switch.
Take note that in the context of this definition, “input voltage” refers to high input voltages between the PCM and the cruise control multifunction switch, which voltages derive from several sensors and subsystems when the cruise control system is activated, such as the- Vehicle speed sensor Transmission range (gear position) sensor Throttle position sensor Cruise control activation switch Clutch pedal mounted cruise control deactivation switch on applications with manual transmissions Brake pedal -, or master cylinder mounted cruise control deactivation switch on applications with automatic transmissions.
Note that on some applications, the cruise control deactivation switch is incorporated into the brake light switch. Brake light switch. Note that on some applications, the cruise control deactivation switch is hard-wired into the brake light switch/circuit, even though the two switches are not always integrated. Typically, steering wheel mounted cruise control multifunction switches include controls for all the functions required to control the cruise control system.
These controls include buttons/switches to- Activate the cruise control system Set and maintain the vehicles’ speed between the minimum allowable, and the maximum rated speed Increase the vehicles’ speed Decrease the vehicles’ speed Deactivate the cruise control system Cancel the cruise control system From the above it should be obvious that the effective/correct operation of the cruise control system on any application requires that the correct signal and return voltages in ALL of the dozens of circuits that pass through the multifunction switch fall within the manufacturers’ specified values when they re