P0585 Cruise Control Multi-Function Input A/B Correlation
OBD-II Trouble Code Technical Description
Cruise Control Multi-Function Input A/B Correlation
What does that mean?
This generic powertrain diagnostic trouble code (DTC) typically applies to many OBD-II vehicles. That may include but is not limited to vehicles from Dodge, Jeep, Chrysler Ram, Ford, Chevy, Chevrolet, etc.
When a code P0585 is stored, it means that the powertrain control module has detected a discrepancy between correlating voltage inputs of the cruise control multi-function switch.
Input A/B (or A and B) references a specific but separate set of input circuits. Consult a reliable source of vehicle information to determine exactly which circuits are indicated with this code.
The cruise control (or speed control) system is controlled by the PCM, using inputs from the multi-function switch. The multi-function switch is so called because it controls functions in multiple systems. For instance, it may provide input signals for the cruise control system, the turn signals, and the windshield wiper system. Typically, it only acts as a lever for the turn signals but may also house the actual turn signal switch.
The driver provides manual inputs using the multi-function switch. These input signals are forwarded to the PCM, which applies the appropriate voltage signal to a cruise control servo motor. These inputs include a command to maintain current vehicle speed, resume a previously maintained vehicle speed, accelerate to increase vehicle speed, or disengage acceleration in order to coast and decrease vehicle speed. Of course, depressing the brake pedal should disengage the cruise control system. Cruise control systems do not generally become active until vehicle speed exceeds 35 mph.
The PCM adjusts cruise control servo motor voltage to achieve the appropriate throttle position for maintaining the desired vehicle speed.
If the PCM detects an input voltage signal that is not within programmed specifications, or if the vehicle speed cannot be maintained using the cruise control system, a code P0585 will be stored and a malfunction indicator lamp (MIL) may be illuminated. Multiple drive cycles with a failure may be required for MIL illumination.
Cruise control stalk:
What is the severity of this DTC?
Since the P0585 pertains only to the cruise control system, it should not be categorized as severe.
What are some of the symptoms of the code?
Symptoms of a P0585 trouble code may include:
Inoperative cruise control system Erratic speedometer/odometer operation Flashing or unresponsive cruise control indicator lamp Other stored codesWhat are some of the common causes of the code?
Causes for this code may include:
Defective multi-function switch Bad cruise control servo motor Open or shorted circuits in the cruise control system Faulty cruise control module, PCM, or programming errorWhat are some P0585 troubleshooting steps?
If the vehicle in question is equipped with a drive-by-wire throttle control system, and related codes are stored, diagnose and repair those before attempting to diagnose the P0585.
If throttle position sensor (TPS) codes are stored, they must also be diagnosed and repaired before diagnosing this code.
A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle information will be required to diagnose a code P0585.
After a visual inspection of cruise control system wiring and connectors, connect the scanner to the vehicle diagnostic port and retrieve all stored codes and freeze frame data. Record this information as it may prove useful as your diagnosis unfolds. Clear the codes and test drive the vehicle normally until the PCM either enters readiness mode or the P0585 is reset. If the former occurs, you have an intermittent condition and it
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