Error Code P0566 is defined as Cruise Control Off Signal Malfunction. This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II system, especially those vehicles made since 1996 up to present. It commonly applies but not limited to Audi, Chevrolet, Citroen, Ford, Hyundai, Peugeot, Volkswagen, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

Cruise Control comes with multiple functions; the driver can set a specific speed for the vehicle and maintain it using numerous sensors, modules, switches, and various components, as well as modify the speed electronically (using “set –“ and “set +”), and even temporarily modify speed while storing previous speed (often used in passing vehicles, unexpected slowing or stopping), etc.

Since this code is contained within one switch/component, it is important to locate the mechanical inputs (buttons, switches, talks, etc.) involved. With that said, some common names for the said component are: Multi-function switch, Cruise control switch, Cruise control module, Steering wheel controls, Accessory switch, etc.

When the Error Code P0566 is stored, that means the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) has detected a malfunction within the signal circuit, specifically within the Off signal of the “On/Off” circuit.

Other related error codes include:

  • Error Code P0565
  • Error Code P0567
  • Error Code P0568
  • Error Code P0569
  • Error Code P0570

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other common symptoms include:

  • Defective cruise control
  • Cruise control light in the dash is constant or not coming
  • Cruise control cannot be set to desired speed or speed is erratic
  • Non-operative cruise control system (i.e. Accel, Coast, Resume, Set, +, -)

Possible Causes

  • Damaged or defective cruise control switch or buttons
  • No effective electrical connection in the connector(s)
  • Chafed, damaged, open, shorted wires within the cruise control harness
  • Contaminated cruise control switch assembly (coffee, soda, juice)
  • Defective cruise control module
  • A problem in the BCM (Body Control Module)
  • Overheating parts causing malfunction
  • Problems in the PCM (rare)

How to Check

First, check the cruise control switch/module, make sure the buttons and controls function properly. In many cases, buttons are missing, stuck in one position, or loose which is why it’s not making proper electrical connections. Dirt and particles that cause contamination can also lead to problems. Record all cruise control functions and their malfunctions or abnormalities.

If the cruise control light comes on in the instrument cluster when the cruise is manually activated, then it’s in good shape. If it does NOT, then verify if there’s a fuse. This information can be found in your vehicle’s service manual. Any blown fused must be replaced by a new and manufacturer-approved fuse.

Access the harness to the cruise control switch/module. In most cases, you would have to remove dash parts (steering column, steering wheel, airbag, etc.). To find the specific wire involved in the fault, you will need a proper wiring harness for your vehicle. This can vary significantly given many reasons. Again, refer to your service manual before executing this step.

Make sure your ABS (anti-lock brake system) is in good shape, and there are no ABS light on your dash. ABS uses multiple sensors including speed sensors, which if it’s malfunctioning, could fool the computer into thinking the vehicle is going faster or slower than the actual speed.

How to Fix

  • Replacement of defective cruise control switch or buttons
  • Repair or replacement of faulty wiring issues, corroded connectors, open or shorted wires
  • Repair of damaged cruise control system connectors
  • Cleaning of cruise control switch assembly
  • Replacement of damaged fuse, and repairing the underlying issue that caused a blown fuse

Severity for this code is considered low, as you can still use the vehicle even when the cruise control system loses its function. If left unaddressed, however, this code can lead to further electrical damage to the vehicle’s electrical system.

The most common misdiagnosis for this code is not checking for blown fuses. Thus, it must be thoroughly checked before replacing any parts.