What Does P0594 Mean?
The cruise control servo control circuit has an open circuit or general malfunction. The servo (or actuator) is the device that physically controls the throttle position to maintain the set cruise speed. On electronic throttle vehicles, this code relates to the electronic throttle body control signal from the cruise module. The driver will be unable to engage or maintain cruise control.
Common Causes
30%
Failed cruise control servo/actuator motor (open coil or seized mechanism)
25%
Open or broken wire in the servo control circuit
20%
Corroded or disconnected servo connector
15%
Blown fuse in the cruise control servo power supply circuit
10%
PCM or cruise control module driver failure
Diagnostic Steps
1
Check the cruise control servo fuse — locate it in the fuse panel using the owner's manual diagram and verify continuity with a test light or DVOM.
2
Locate the cruise control servo (typically mounted on the firewall or fender well on cable-throttle vehicles) and check for 12V power and ground at the connector with the cruise system commanded on.
3
Measure the servo motor winding resistance — typical values are 30-60 ohms depending on the application; OL indicates an open motor winding.
4
Inspect the servo cable (if equipped) for binding, fraying, or disconnection from the throttle linkage — a seized cable can overload and burn out the servo motor.
5
On electronic throttle body vehicles, check the communication between the cruise module and the electronic throttle control — verify proper CAN or analog signal at the throttle body connector.
Estimated Repair Cost
$150 - $600
Parts + labor, varies by vehicle and location
The cruise control servo control circuit has an open circuit or general malfunction. The servo (or actuator) is the device that physically controls the throttle position to maintain the set cruise speed. On electronic throttle vehicles, this code relates to the electronic throttle body control signa...
The most common cause of P0594 (Cruise Control Servo Control Circuit / Open) is: Failed cruise control servo/actuator motor (open coil or seized mechanism)
Typical repair costs for P0594 range from $150 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. Cruise control will not engage or maintain speed. There is no risk of unintended acceleration because an open circuit means the servo cannot apply throttle. Normal throttle operation through the accelerator pedal is unaffected.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0594 to identify the root cause.
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Quick Info
Category
Powertrain
System
Cruise Control / Speed Control
Difficulty
Type
Generic (SAE)
Recommended Tools
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