Description of the P0579 fault code.
OBD2 Error Codes

P0579 Cruise control system malfunction - multifunction switch “A” input - circuit range/performance 

26.05.2022 /

P0579 – OBD-II Trouble Code Technical Description

Trouble code P0579 indicates that the vehicle's computer has detected a problem with the cruise control multifunction switch input circuit.

What does the fault code mean P0579?

Trouble code P0579 indicates a problem with the vehicle's cruise control multifunction switch input circuit. This switch is the key element for controlling the cruise control system, allowing the driver to set, maintain and change the vehicle's speed. If the vehicle's computer detects a problem in this circuit, it will generate a P0579 code and activate the Check Engine Light. This alerts the driver that there is a problem with the cruise control system that may require repair or replacement of the multifunction switch.

Fault code P0579.

Possible reasons

Possible reasons for DTC P0579 may include the following:

  • Faulty multifunction switch: The switch itself may be damaged or have internal problems, causing its input circuit to not operate properly.
  • Damaged or broken wiring: The wiring connecting the multifunction switch to the vehicle control module (PCM) may be damaged, open or shorted, causing P0579.
  • Problems with contacts: Corrosion, oxidation or poor contact in the connectors or contact plates of a multi-function switch may cause its input circuit to malfunction.
  • Faulty vehicle control module (PCM): In rare cases, the problem may be due to a malfunction in the PCM itself, causing the signals from the multi-function switch to be incorrectly sensed.
  • Problems with other components of the cruise control system: Faults in other components, such as brake switches or sensors, can also cause P0579 if they affect the operation of the multifunction switch.

To accurately determine the cause of the malfunction and eliminate it, it is recommended to contact a professional auto mechanic or service center.

What are the symptoms of a fault code? P0579?

Symptoms for trouble code P0579 may vary depending on the specific vehicle and the features of the cruise control system, some of the possible symptoms are:

  • Inoperative cruise control system: One of the most obvious symptoms is the inability to turn on or use the cruise control system. This may mean that the cruise control buttons are not responding or the system is not maintaining the set speed.
  • Faulty brake lights: If the multi-function switch also controls the brake lights, their operation may be impaired. For example, the brake lights may not come on at all or stay on constantly, even when the brake pedal is released.
  • Dashboard error: If a problem with the cruise control system is detected, the vehicle's computer may activate the Check Engine light on the dashboard.
  • Problems with other switch functions: The multi-function switch can also control other functions in the car, such as turn signals, headlights or windshield wipers. Symptoms may include turn signals, headlights, or windshield wipers that don't work or don't work properly.
  • Other fault codes appear: In addition to P0579, the vehicle's diagnostic system may also generate other trouble codes related to problems with the cruise control system or electrical circuit.

How to diagnose a fault code P0579?

Diagnosing the P0579 trouble code involves a series of steps to identify and resolve the problem:

  1. Reading the error code: You must first use a diagnostic scan tool to read the P0579 trouble code and any other codes that may have been generated.
  2. Checking the multifunction switch: The multi-function switch responsible for controlling the cruise control system must be checked for proper operation. This may include testing each function of the switch, such as setting the speed, turning the system on and off, and other functions it can perform.
  3. Checking wiring and connections: The wiring connecting the multifunction switch to the engine control module (PCM) should be inspected for opens, corrosion, or other problems. Connectors and contacts must be inspected for damage.
  4. Checking the brake switches: Brake switches can also be linked to the cruise control system. Their functionality must be checked, as incorrect operation of the brake switches can lead to the P0579 code.
  5. Checking the Engine Control Module (PCM): In rare cases, the problem may be due to a problem with the PCM itself. After all the previous steps, if the cause of the malfunction has not been identified, the PCM should be diagnosed to check its functionality.
  6. Repair or replacement of components: After thorough diagnosis and identification of the cause of the problem, it may be necessary to repair or replace damaged components such as the multi-function switch, wiring or brake switches.
  7. Clearing the error code: After all repairs have been completed, the DTC must be cleared from the PCM memory using a diagnostic scan tool.

To carry out diagnostics, it is recommended to contact a qualified auto mechanic or service center.

Diagnostic errors

When diagnosing trouble code P0579, various errors may occur:

  • Incorrect interpretation of error code: An unqualified technician or diagnostician may misinterpret the meaning of the P0579 code or miss other related problems, which may result in incorrect diagnosis and repair.
  • Skip Physical Component Check: Sometimes technicians may rely solely on reading error codes without physically checking components such as the multi-function switch, wiring, and brake switches. This may result in missing the actual cause of the problem.
  • Incorrect component replacement: Instead of carrying out a full diagnosis, components may be replaced unnecessarily, which may result in additional costs and not solve the underlying problem.
  • Skip other related issues: Trouble code P0579 may be related to other components of the cruise control system or the vehicle's electrical system. Incorrect diagnosis may result in these problems being missed.
  • Improper repair work: If the problem is not properly diagnosed and corrected, it can lead to additional malfunctions and even accidents on the road.
  • Reactivation of the error: Incorrect repair or incorrect installation of new components may cause the error to reactivate after repair.

To prevent these errors, it is important to contact an experienced and qualified auto mechanic or service center for diagnosis and repair.

How serious is the fault code? P0579?

Trouble code P0579, indicating a problem with the cruise control multifunction switch input circuit, although not a critical alarm, requires careful attention and repair. Here are a few reasons why this code should be taken seriously:

  • Inoperative cruise control system: One of the main symptoms of the P0579 code is the cruise control system not working. This can significantly impair the car's handling on the road, especially on long trips.
  • Potential Security Issues: A malfunctioning cruise control system can cause driver fatigue and difficulty controlling vehicle speed, especially on long straight stretches of road. This may increase the risk of an accident.
  • Deterioration in fuel economy: The cruise control system helps maintain a constant speed, which contributes to economical fuel consumption. Failure to operate may result in higher fuel consumption due to speed instability.
  • Potential problems with brake lights: If the multi-function switch also controls the brake lights, a non-functioning cruise control system may cause problems with their operation, increasing the risk of an accident on the road.

Although the P0579 code is not an emergency, it should be looked into carefully and promptly

What repair will help eliminate the code? P0579?

Troubleshooting trouble code P0579 may include the following steps:

  1. Replacing the Multifunction Switch: If the multifunction switch is found to be the source of the problem, it should be replaced with a new, working unit. This may require removing the steering column and accessing the shifter.
  2. Checking and repairing wiring: The wiring connecting the multifunction switch to the engine control module (PCM) should be checked for breaks, damage or corrosion. If necessary, the wiring is repaired or replaced.
  3. Checking and replacing brake switches: Brake switches, which may also be linked to the cruise control system, must be checked for proper operation. If problems are found, they must be replaced.
  4. Diagnosis and replacement of the engine control module (PCM): In rare cases, the problem may be due to a problem with the PCM itself. Once this problem is diagnosed and confirmed, the PCM may need to be replaced.
  5. Checking other cruise control system components: It is possible that the problem is not only with the multifunction switch, but also with other components of the cruise control system, such as the brake switches. These components must also be checked and replaced if necessary.

Repair work may vary depending on the specific cause of the problem. For proper diagnosis and repair, it is recommended that you contact a qualified auto mechanic or service center.

What is P0579 Engine Code [Quick Guide]

P0579 – Brand-specific information

Trouble code P0579 usually indicates problems with the cruise control multifunction switch. The decoding for this code may vary slightly depending on the vehicle manufacturer, the decoding for several specific brands:

It is recommended to consult the manufacturer's official documentation or vehicle service specialists to obtain accurate information about decoding the error code for a specific vehicle brand.

One comment

  • anonym

    07.06.2022 at 19:02

    Hello I ask x please an info on code p 0579 on my 2.7 Grand cherocchi Diesel 2003 with light problem RM does not work, I am a retired mechatronic! Could this code be connected P0579 does it have this fault?

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