OBD-II Code P0591 — What It Means & How to Fix It

What Does This Error Mean?

P0591 means the cruise control multi-function switch circuit is reading a voltage that is outside its expected range. Your car's computer monitors the switch voltage constantly. When the reading is too high, too low, or erratic — without a clear match to any known button position — P0591 is triggered. Cruise control will be disabled. Your engine and brakes are unaffected, so driving is still safe.

Affected Models

All vehicles 1996+
Common in GM trucks and SUVs
Common in Ford vehicles
Common in Chrysler and Dodge vehicles
Common in any vehicle with a resistor-based cruise control switch

Common Causes

Worn or failing cruise control switch with degraded internal resistors
Corroded contacts inside the switch that change the resistance reading
Damaged wiring between the switch and the powertrain control module
Water or moisture inside the switch housing changing resistance values
A faulty clock spring (spiral cable) causing an intermittent open circuit

How to Fix It

Use a scan tool to read the live cruise control switch voltage data parameter. This shows the voltage the PCM sees in real time as you press each button on the switch.

Each button position should produce a specific, repeatable voltage. A reading that jumps around or stays at a fixed value when no buttons are pressed points to a bad switch.
Check the wiring connector at the base of the steering column or at the switch itself. Look for corrosion, bent pins, or broken wires. Unplug and re-plug the connector to reseat it.

A thin layer of green or white corrosion on the pins is enough to throw the resistance reading off.
Inspect the clock spring assembly if the switch checks out. The clock spring is the coiled ribbon cable that routes electrical signals through the rotating steering wheel. A worn clock spring causes intermittent signal loss.

Signs of a failing clock spring include: horn works sometimes, airbag warning light, or cruise control buttons that are intermittent.
Replace the cruise control switch if the live voltage data shows abnormal readings at any button position. This is the most common fix for P0591.

Most switches are straightforward to replace on a stalk-style setup. Steering wheel-mounted switches may require airbag precautions.
Clear the code after repair and perform a full cruise control function test — set speed, resume, accelerate, decelerate, and cancel — to confirm everything works.

If the code returns within a day or two of driving, recheck the connector and wiring before replacing expensive components.

When to Call a Professional

If replacing the switch and checking wiring does not resolve P0591, a shop can perform a live voltage sweep test. This confirms whether the signal voltage from each button position matches the specification. Diagnosis typically costs $75 to $125. Switch replacement parts range from $30 to $180 depending on the vehicle.

Frequently Asked Questions

What does 'range/performance' mean in this code?

It means the signal is present but not behaving as expected. For example, the voltage may be within a valid range but does not match any known button position. Or it may jump around instead of holding a steady value. This is different from a 'low' or 'high' code, where the voltage is completely out of range.

Can I still use cruise control with P0591?

No. When P0591 is active, the system disables cruise control entirely as a safety measure. You need to clear the fault before cruise control will work again.

How long does it take to replace a cruise control switch?

For a stalk-mounted switch, replacement usually takes 30 to 60 minutes. For a steering wheel-mounted switch, add time for removing the steering wheel and airbag — typically 1 to 2 hours total at a shop.