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DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P0595

P0595Cruise Control Servo Control Circuit Low

P0595 means the engine computer has detected a low-voltage condition on the cruise control servo control circuit, which is the wire the powertrain control module uses to command the servo to open or close the throttle for cruise operation. The computer monitors the circuit and sets this code when the signal voltage falls below the expected range, indicating an open circuit, a short to ground, or a failed servo.

SystemPowertrain
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • Cruise control does not engage or drops out unexpectedly while driving
  • Cruise control indicator light may flash or stay off when you try to set speed
  • Often no symptoms besides the warning light, with the vehicle driving normally otherwise
  • The engine may feel sluggish or hesitate if the servo also affects throttle response
  • A stored code may be the only clue if the servo is electrically failed but mechanically intact

Common causes, most likely first

  1. Broken, corroded, or disconnected wire in the cruise control servo control circuit
  2. Failed cruise control servo motor or actuator
  3. Poor electrical connection at the servo harness connector
  4. Short to ground in the control wire between the PCM and servo
  5. Faulty powertrain control module (PCM) driver circuit, though this is less common
  6. Water intrusion or corrosion in the servo connector or wiring harness

How to diagnose and fix it

  1. Inspect the cruise control servo connector and wiring for visible damage, corrosion, or looseness
  2. Check the servo control circuit for continuity and short to ground using a digital multimeter
  3. Test the servo motor itself by applying power and ground directly to confirm it moves
  4. Verify the PCM is commanding the servo by back-probing the control wire with a scan tool or oscilloscope
  5. Repair or replace any damaged wiring or connectors found during testing
  6. Replace the cruise control servo if it fails electrical or functional testing
  7. Clear the code and test-drive the vehicle to confirm the repair and ensure the code does not return

What the servo control circuit really does

  • A low-voltage code often comes from a simple open circuit or bad ground rather than a failed servo, so always check wiring before replacing parts.
  • The servo control circuit is separate from the cruise control switch circuit, so a code for the servo does not mean the switches are faulty.
  • Some vehicles use the throttle actuator itself for cruise control, so a P0595 may point to a problem in the electronic throttle system rather than a standalone servo.
  • Corrosion inside the servo connector is a common hidden cause that can mimic a failed servo and is easily missed during a quick visual inspection.
  • A scan tool that can read live cruise control data is far more useful than a basic code reader for diagnosing this fault.

Can I keep driving with P0595?

The vehicle remains safe to drive because the cruise control system is disabled and normal throttle operation is unaffected, but avoid using cruise control until the fault is repaired. If the engine also runs poorly, have it checked promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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