P0591 – Cruise Control Multi-Function Input “B” Circuit Range/Performance

P0591 is a diagnostic trouble code that points to a problem with your cruise control system, specifically the “B” circuit of the cruise control multi-function switch. While it usually won’t leave you stranded, it can disable cruise control and hint at deeper electrical or wiring issues if ignored. In this guide, you’ll learn what P0591 actually means, the most common causes and symptoms, how a mechanic would diagnose it, and what repairs typically cost so you can decide whether to tackle it yourself or head to a shop.

What Does P0591 Mean?

P0591 is defined as “Cruise Control Multi-Function Input ‘B’ Circuit Range/Performance.” In plain language, your vehicle’s ECU (engine control unit) is seeing an electrical signal from the cruise control switch that’s outside the expected range. That could mean the switch is failing, the wiring is damaged, or there’s corrosion or resistance somewhere in the circuit.

This code is focused on the “B” circuit, which usually corresponds to a specific function of the cruise switch, such as SET/COAST or RESUME/ACCEL, depending on the manufacturer. The ECU constantly monitors voltage from this switch; if it sees a value that doesn’t match the programmed range, it sets P0591 and usually disables cruise control for safety.

Quick Reference

  • Code: P0591
  • Definition: Cruise Control Multi-Function Input “B” Circuit Range/Performance
  • Primary System: Cruise control / steering wheel switch
  • Severity: Low for drivability, moderate for safety and convenience
  • Typical Fixes: Switch replacement, wiring repair, connector cleaning

Real-World Example / Field Notes

In the shop, P0591 often shows up on vehicles where the owner says, “My cruise control stopped working out of nowhere.” A common pattern is a steering wheel switch that feels a little “mushy” or intermittent before it fails completely. On some GM and Hyundai models, I’ve seen the wiring in the steering wheel clock spring chafe or break, causing an open or out-of-range signal that triggers P0591.

Another real-world scenario is after a steering wheel replacement, airbag service, or aftermarket stereo/remote start install. If a connector isn’t fully seated or a wire gets pinched, the ECU will see bad data from the cruise switch. A quick visual inspection and a multimeter check at the switch connector often pinpoints the problem faster than just throwing parts at it.

Symptoms of P0591

  • Cruise control inoperative – Cruise won’t set or won’t turn on at all.
  • Intermittent cruise operation – Cruise works sometimes, then drops out randomly.
  • Malfunction indicator – Check Engine Light or a specific cruise control warning may illuminate.
  • Non-responsive buttons – One or more steering wheel cruise buttons don’t respond when pressed.
  • Unusual switch feel – Cruise switch feels loose, sticky, or inconsistent compared to other buttons.
  • Related electrical quirks – Possible issues with horn, audio controls, or airbag light if the clock spring is involved.
  • Stored cruise-related codes – P0591 may appear with other cruise or switch circuit codes.

Common Causes of P0591

Most Common Causes

  • Faulty cruise control switch: Internal wear, contamination, or broken contacts in the steering wheel switch are very common, especially on higher-mileage vehicles.
  • Damaged or worn clock spring: The clock spring (spiral cable behind the steering wheel) can crack or break, interrupting the signal from the switch to the ECU.
  • Loose or corroded connectors: Moisture, spilled drinks, or age can corrode connectors at the steering wheel, clockspring, or under-dash harness.
  • Wiring damage: Chafed, pinched, or broken wires in the steering column or dash harness can cause out-of-range voltage or intermittent signals.
  • Aftermarket accessory interference: Poorly installed remote start, audio controls, or steering wheel upgrades can disturb the cruise control circuit.

Less Common Causes

  • ECU/PCM internal fault: Rare, but a failed input circuit inside the ECU can misread a good switch signal.
  • Incorrect steering wheel or switch retrofit: Swapping in a different wheel or switch assembly that doesn’t match the vehicle’s wiring or resistance values.
  • Ground issues: High resistance at shared grounds can skew the reference voltage for the cruise switch.
  • Water intrusion: Leaks into the cabin or around the steering column can cause intermittent shorts or corrosion.
  • Software/firmware anomalies: On some late-model vehicles, a TSB (technical service bulletin) may call for a control module reflash.

Diagnosis: Step-by-Step Guide

To diagnose P0591 properly, you’ll want at least a basic scan tool that can read live data, a digital multimeter, and access to wiring diagrams for your specific vehicle. A factory-level or good aftermarket scan tool that can read steering wheel switch inputs and Mode $06 data makes the job easier, but you can still do a lot with simple tools and patience.

  1. Confirm the code and record data: Connect your scan tool, confirm P0591 is present, and note any other related codes. Check freeze-frame data to see when the fault occurred (speed, RPM, switch state).
  2. Check cruise control operation: With the engine running and vehicle safely parked, try all cruise buttons (ON/OFF, SET, RESUME). Note which functions don’t respond or act intermittently.
  3. Inspect steering wheel and column: Look for signs of previous work, aftermarket accessories, or damage. Check that the steering wheel isn’t loose and that no trim is rubbing or pinching wiring.
  4. Visual connector check: If you’re comfortable removing the steering column covers, inspect the switch and clock spring connectors. Look for corrosion, bent pins, loose locks, or broken tabs.
  5. Check switch input with scan tool: Many scan tools can show live data for “Cruise Switch A/B” states. Press each button and watch if the ECU sees the command change. If one function never changes, that’s your suspect circuit.
  6. Test switch resistance/voltage: With the battery disconnected and the switch unplugged, use a multimeter to measure resistance between the specified terminals while pressing each button. Compare readings to specs in a service manual. Out-of-spec values indicate a bad switch.
  7. Inspect and test clock spring: If multiple steering wheel functions (horn, audio controls, airbag light) act up, the clock spring is a prime suspect. Check continuity through the relevant circuits according to the wiring diagram.
  8. Check wiring continuity to ECU: If the switch and clock spring test good, backprobe the harness and verify continuity and proper voltage from the switch connector to the ECU input pin. Repair any opens, shorts to ground, or shorts to power.
  9. Clear codes and road test: After repairs, clear P0591 and perform a road test. Engage cruise at highway speed and verify all functions work and the code does not return.

Pro tip: If you replace the clock spring or remove the steering wheel, always disconnect the battery and wait several minutes before working. This prevents accidental airbag deployment and protects sensitive electronics.

Possible Fixes & Repair Costs

Most P0591 repairs are straightforward once you pinpoint the faulty part. Typical fixes include replacing the cruise control switch on the steering wheel, installing a new clock spring, cleaning or tightening connectors, or repairing damaged wiring. In rare cases, an ECU replacement or reflash may be required.

  • Cruise control switch replacement: Parts typically $40–$180; labor $80–$200 depending on access and whether the airbag must be removed.
  • Clock spring replacement: Parts usually $80–$300; labor $120–$250 due to airbag and steering wheel removal.
  • Wiring/connector repair: Often 0.5–2.0 hours of labor; expect $80–$300 depending on complexity and location.
  • ECU diagnosis/reflash or replacement: Reflash $100–$200; replacement with programming can run $500–$1,200+ but is rare for this code.

Overall, most owners see repair costs for P0591 in the $150–$500 range at a typical shop. Costs vary by vehicle make, dealer vs. independent shop rates, part availability, and whether multiple components (like both switch and clock spring) need replacement.

Can I Still Drive With P0591?

Yes, you can usually keep driving with a P0591 code without immediate risk of engine damage. The main impact is that your cruise control may not work or may be disabled by the ECU. For most drivers, that’s an inconvenience rather than a safety crisis, especially if you mostly drive in town.

However, if the underlying cause is a failing clock spring or wiring in the steering column, other systems can be affected over time, such as the airbag, horn, or steering wheel controls. If you notice multiple steering wheel functions acting up, you should address P0591 sooner rather than later.

What Happens If You Ignore P0591?

If you ignore P0591, you’ll likely just live without cruise control, but the real risk is allowing a small electrical fault to grow into a bigger one. A deteriorating clock spring or harness can eventually affect the airbag circuit, horn, or other controls. In the worst case, you could end up with an airbag warning light, failed inspection, or more expensive wiring repairs down the road.

Need wiring diagrams and factory-style repair steps?

Powertrain faults often require exact wiring diagrams, connector pinouts, and guided test steps. A repair manual can help you confirm the cause before replacing parts.

Factory repair manual access for P0591

Check repair manual access

Compare nearby cruise multi-function trouble codes with similar definitions, fault patterns, and diagnostic paths.

  • P0579 – Cruise Control Multi-Function Input “A” Circuit Range/Performance
  • P0525 – Cruise Control Servo Control Circuit Range/Performance
  • P0564 – Cruise Control Multi-Function Input “A” Circuit
  • P0593 – Cruise Control Multi-Function Input “B” Circuit High
  • P0592 – Cruise Control Multi-Function Input “B” Circuit Low
  • P0590 – Cruise Control Multi-Function Input “B” Circuit Stuck

Key Takeaways

  • P0591 means the ECU is seeing an out-of-range signal from the cruise control multi-function switch “B” circuit.
  • The most common culprits are a failing steering wheel cruise switch, a worn clock spring, or wiring/connector issues.
  • Symptoms usually center on inoperative or intermittent cruise control, with little effect on basic drivability.
  • Diagnosis involves checking switch operation, using a scan tool for live data, and testing wiring continuity and resistance.
  • Typical repair costs fall between $150 and $500, depending on which component is at fault and labor rates in your area.

Vehicles Commonly Affected by P0591

P0591 can appear on many makes that use steering wheel-mounted cruise control switches and clock springs. In practice, it’s commonly seen on:

  • GM vehicles: Chevrolet, GMC, Buick, and Cadillac trucks and SUVs with steering wheel controls.
  • Hyundai and Kia: Sedans and crossovers where steering wheel switch and clock spring issues are relatively common.
  • Ford and Lincoln: F-150, Explorer, and various SUVs with integrated cruise and audio controls.
  • Chrysler, Dodge, and Jeep: Minivans, SUVs, and trucks with multi-function steering wheels.
  • Some European and Japanese models: VW, Subaru, and others, especially when aftermarket accessories have been added.

Any vehicle with a multi-function cruise switch and clock spring can potentially set P0591 if the switch, wiring, or connectors degrade over time.

FAQ

Can I clear P0591 myself and keep driving?

You can clear P0591 with a basic OBD-II scanner, and the cruise control may work again temporarily. But if the underlying fault is still there, the code will usually return. It’s fine to drive short term, but you should still diagnose and repair the root cause.

Is P0591 related to the airbag or horn?

Indirectly, it can be. The cruise switch wiring often runs through the same clock spring assembly as the airbag and horn circuits. If the clock spring is failing, you may see cruise issues (P0591), a horn that doesn’t work, or an airbag warning light together.

How do I know if the cruise switch or clock spring is bad?

If only the cruise buttons act up while the horn, airbag light, and other steering wheel controls work fine, the switch itself is more likely. If multiple steering wheel functions fail or are intermittent, the clock spring becomes the primary suspect. Proper testing with a multimeter and wiring diagram will confirm it.

Can a dead battery or jump-start cause P0591?

A weak battery or jump-start usually doesn’t directly cause P0591, but voltage spikes or low voltage can sometimes expose marginal wiring or switch issues. If the code appeared right after battery work, double-check that no connectors or wiring were disturbed during the process.

Do I need a dealer to fix P0591, or can an independent shop handle it?

Most independent shops can diagnose and repair P0591 without any problem, especially if they have good scan tools and access to wiring diagrams. A dealer may be preferable only if a software update or ECU reflash is required, or if your vehicle is still under warranty.