OBD-II Code P0593 — What It Means & How to Fix It

What Does This Error Mean?

P0593 means the cruise control multi-function switch circuit voltage is too high. The voltage signal coming from the switch is above the maximum the PCM expects to see. This usually happens because of an open circuit (broken wire or bad connector) or a short to voltage in the switch wiring. Cruise control will be disabled while this code is active. Your normal driving is not affected.

Affected Models

All vehicles 1996+
Common in Ford and Lincoln vehicles
Common in GM trucks and vans
Common in Jeep and Dodge vehicles
Common in vehicles with steering wheel-mounted cruise control

Common Causes

Open circuit in the signal wire — broken wire or disconnected connector
Short to battery voltage in the signal wiring
Faulty PCM reference voltage circuit supplying too much voltage
Failed cruise control switch with an internal open in the resistor network
Damaged clock spring causing an intermittent or permanent open in the steering wheel wiring

How to Fix It

Check the cruise control switch connector first. Unplug it and inspect both sides for bent, pulled-back, or missing pins. Reconnect it firmly and see if the code clears.

A partially seated connector is a very common cause of high-circuit codes because an open connection lets the voltage float high.
Inspect the wiring from the switch to the steering column. The wires must flex every time you turn the steering wheel. Over time, they can fatigue and break internally even if the insulation looks intact.

Gently flex the wiring near any bend points while watching the live voltage data on a scan tool. A voltage spike during flexing confirms a broken wire.
Test the clock spring. If your steering wheel horn or other buttons have also been intermittent, the clock spring is likely failing. A broken clock spring can cause an open circuit in any wire routed through the steering wheel.

Clock springs are replaced as a complete assembly. The job involves disabling the airbag — use caution or have a shop handle it.
If the wiring and clock spring are okay, test the switch itself. Unplug it and measure resistance across the switch terminals while pressing each button. Each position should produce a specific resistance value.

Compare readings against your vehicle's wiring diagram. An infinite resistance (open circuit) reading on one or more positions points to a failed switch.
Replace the faulty component, clear the code, and test all cruise control functions over a short drive to confirm the repair.

Make sure to test the coast/decelerate and resume functions in addition to set/accelerate — these use different resistors in the switch.

When to Call a Professional

If you cannot locate a broken wire or open circuit, a technician can quickly pin-point the fault using a wiring diagram and a multimeter. Clock spring replacement typically costs $150 to $350 in parts and labor. If the PCM reference voltage circuit is suspect, further testing is needed before replacing the module.

Frequently Asked Questions

Can I ignore P0593 and just not use cruise control?

In most cases, yes — this code only affects cruise control and does not impact normal driving. However, if the cause is a damaged wiring harness, ignoring it could allow further damage. It is best to diagnose and fix it when convenient.

Why does a broken wire cause the voltage to go HIGH rather than low?

When a wire breaks (open circuit), the PCM's internal pull-up resistor holds the signal wire at a high voltage. There is nothing to pull it down to the expected level. This is why open circuit faults typically trigger 'high' codes, while shorts to ground trigger 'low' codes.

How do I know if my clock spring is bad?

Common signs include: horn that only works sometimes, airbag warning light on the dash, cruise control buttons that are intermittent, and cruise control codes that come and go. If multiple steering wheel functions are acting up at the same time, the clock spring is a very likely culprit.