P0596 Cruise Control Servo Control Circuit High

P0596 indicates a high condition in the cruise control servo control circuit. The controller sees servo control voltage or feedback above the expected range.

Code details

Generic OBD-II · P0

System: Speed / Idle
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the controller until the servo control circuit is checked for short-to-voltage and ground faults.

Symptoms of P0596

Unstable, high, or low idle, or stalling.
Erratic speedometer, cruise-control, or shift behaviour.
Check-engine light with a hesitation or surge.

Common causes of P0596

A dirty throttle body, idle-control valve, or throttle-position sensor.
A failing vehicle-speed or wheel-speed sensor, or its wiring.
Vacuum leaks or a related sensor forcing the idle/speed strategy.

Useful checks before replacing parts

Review servo command, control voltage, current draw, driver status, cruise enable conditions, vehicle speed, and freeze-frame data.
Inspect for short-to-voltage faults, open grounds, connector corrosion, actuator internal faults, linkage binding, and harness damage near heat.
Command the servo and confirm circuit voltage, current, and actuator movement change as expected.

Related OBD-II codes

These nearby speed / idle entries can help compare wording and pin down the fault area.