P0596 code meaning
Cruise Control Servo Control Circuit High
What P0596 means
Older engines without electronic throttle use a vacuum cruise servo on the throttle cable: a vacuum valve (closed when unpowered) opens the throttle with intake vacuum, a vent valve (open when unpowered) holds or releases it, and a dump valve fed through the brake switch vents it when braking. Where the engine module drives these valves, it checks each circuit and switches cruise off; CARB treats this as emission-neutral, usually without warning lamp. P0596 means the voltage in the servo supply or control circuit is too high, for example a short to positive keeping supply on while braking – safety-relevant, because the brake switch cut-off could then fail; cruise control is locked out. No manufacturer document available to us uses this code.
P0596 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0596
- Cruise control cannot be engaged or switches off
- Cruise indicator goes out or flashes (depending on vehicle)
- Usually no check engine light, code stored only
Common causes of P0596
- Most likelyServo supply line shorted to positive
- PossibleBrake light switch sticking
- PossibleServo faulty
- Less likelyEngine module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cruise control servoBrake light switchServo wiringEngine control module
What each part of P0596 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 96 | The exact fault in that area. |
What to do next
- Note P0596 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0596
What does P0596 mean?
P0596 means "Cruise Control Servo Control Circuit High". Older engines without electronic throttle use a vacuum cruise servo on the throttle cable: a vacuum valve (closed when unpowered) opens the throttle with intake vacuum, a vent valve (open when unpowered) holds or releases it, and a dump valve fed through the brake switch vents it when braking. It is a generic code, so it means the same on every make.
Is it safe to drive with P0596?
P0596 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P0596 fail an emissions test?
P0596 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0596 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0596 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.