P0585 is a diagnostic trouble code that points to a problem in your vehicle’s cruise control system, specifically with the “A/B” input correlation. In plain language, the computer is seeing cruise control signals that don’t agree with each other or don’t make sense based on what you’re doing with the pedals and switches. While this code usually won’t leave you stranded, it can disable cruise control and may hint at deeper electrical or wiring issues. Understanding what P0585 means helps you decide whether you can tackle it yourself or need a professional.
What Does P0585 Mean?
P0585 stands for “Cruise Control Multi-Function Input ‘A’/‘B’ Correlation.” Your vehicle’s ECU (engine control unit) monitors several cruise control inputs: steering wheel buttons, stalk switches, brake pedal switch, and sometimes clutch or cancel switches. These are grouped as different input channels, often labeled “A” and “B.”
When the ECU sees signals from these channels that conflict with each other, are out of expected range, or don’t match vehicle conditions, it sets P0585 and usually disables cruise control as a safety measure. The engine itself often runs fine, but your cruise system won’t behave correctly.
Quick Reference
- Code: P0585
- Meaning: Cruise control multi-function input A/B correlation fault
- System: Cruise control / body electronics
- Severity: Low to moderate (comfort/safety feature affected)
- Typical fix: Switch repair, wiring repair, or clock spring replacement
Real-World Example / Field Notes
In the shop, I most often see P0585 on vehicles where the owner complains that cruise control works “sometimes” or shuts off randomly on the highway. On one mid-2000s SUV, the code traced back to a worn steering wheel clock spring. The horn worked intermittently, airbag light flickered, and cruise buttons were hit-or-miss. Testing showed inconsistent voltage from the cruise switches as the wheel turned. Replacing the clock spring and clearing the code restored full cruise operation with no further issues.
Symptoms of P0585
- Cruise control inoperative – Cruise won’t engage at all when you press the “ON” or “SET” buttons.
- Intermittent cruise operation – Cruise works sometimes, then drops out or refuses to set speed.
- Unexpected cruise canceling – Cruise disengages on its own without you touching the brakes or cancel switch.
- Warning lights – Check Engine Light may come on; some vehicles may show a cruise or traction warning.
- Other steering wheel issues – Horn, radio controls, or airbag light acting up (often points to a bad clock spring).
- Brake light or pedal switch problems – Brake lights staying on or not working correctly in some cases.
- No drivability change – Engine power and shifting usually feel normal; the main complaint is cruise not working.
Common Causes of P0585
Most Common Causes
- Faulty cruise control switch or buttons – Worn or contaminated contacts inside the steering wheel or stalk switch can send erratic signals.
- Defective clock spring – The ribbon cable inside the steering wheel that carries signals to the buttons can crack or break, causing intermittent connections.
- Brake pedal switch issues – A misadjusted or failing brake switch can tell the ECU you’re braking when you’re not, confusing the cruise logic.
- Damaged wiring or connectors – Chafed, corroded, or loose wiring between the switches and ECU can create incorrect voltages or open circuits.
- Poor ground or power supply – Weak grounds or low voltage to the cruise circuit can make inputs fall outside the expected range.
Less Common Causes
- Faulty clutch pedal switch (manual transmissions) – If the ECU thinks the clutch is pressed when it’s not, cruise may be disabled.
- Aftermarket accessories – Poorly installed remote starters, alarms, or audio systems can tap into the wrong wires and corrupt cruise signals.
- Internal ECU fault – Rare, but a failing engine or body control module can misread or misinterpret the cruise inputs.
- Water intrusion or corrosion – Leaks into the steering column, dash, or junction blocks can corrode connectors and alter signal values.
- Incorrect steering wheel or switch retrofit – Swapping steering wheels or adding cruise to a non-cruise car without proper wiring can trigger correlation errors.
Diagnosis: Step-by-Step Guide
To diagnose P0585 correctly, you’ll want a decent scan tool (ideally one that can read live data and Mode $06), a digital multimeter, basic hand tools, and wiring diagrams for your specific vehicle. If you’re comfortable with electrical testing and removing steering column covers, you can do a lot of this at home.
- Confirm the code and check for companions
Connect a scan tool, read all stored and pending codes, and note any related cruise, brake switch, or communication codes (like P0571). Clear codes and see if P0585 returns quickly. - Verify cruise control operation
On a safe road, try to engage cruise: turn it on, set speed, resume, and cancel. Note exactly what works and what doesn’t. Intermittent behavior often points to a switch or clock spring. - Check brake and clutch switch function
Confirm brake lights work correctly. Use the scan tool to monitor brake and clutch switch status while pressing and releasing pedals. A switch that flickers or doesn’t change state is suspect. - Inspect steering wheel and column
Wiggle the steering wheel slightly while pressing cruise buttons. If cruise works only at certain wheel positions, the clock spring is a prime suspect. Look for any airbag or horn issues as supporting evidence. - Read live data for cruise inputs
Use the scan tool to watch each cruise input (ON, SET, RESUME, CANCEL) while you operate the controls. The ECU should see clean, consistent changes. Missing or erratic signals indicate a switch or wiring problem. - Test the cruise switch circuits
With the battery disconnected (airbag safety), remove the steering wheel or column covers as needed. Use a multimeter to check resistance or voltage at the cruise switch connector while pressing each button, comparing to spec. - Inspect wiring and connectors
Follow the harness from the steering column and pedal area to the junction block or ECU. Look for rubbed-through insulation, pinched wires, green corrosion, or loose connectors. Repair any damage and secure the harness. - Evaluate the clock spring
If multiple steering wheel functions are intermittent (horn, radio controls, airbag light, cruise), test continuity through the clock spring according to the service manual. Replace it if readings are out of spec or open. - Check Mode $06 and freeze frame
Some scan tools let you see the exact conditions when P0585 set (speed, pedal position, switch states). This can narrow down whether the issue happens only at certain speeds or steering angles. - Re-test after repairs
Clear codes, perform a road test, and try all cruise functions again. If P0585 does not return and cruise operates normally, the repair is successful.
Pro tip: Anytime you work around the steering wheel or clock spring, disconnect the battery and wait at least 10–15 minutes before removing airbag components. This prevents accidental deployment and protects you and the vehicle.
Possible Fixes & Repair Costs
Most P0585 repairs involve restoring proper cruise control inputs and wiring integrity. Typical fixes include replacing a faulty cruise control switch assembly, installing a new brake or clutch pedal switch, repairing or replacing damaged wiring/connectors, or replacing the steering wheel clock spring. In rare cases, an ECU or body control module may need programming or replacement.
Repair costs vary by vehicle and labor rates. As a rough guide, you might see:
- Cruise switch replacement: $100–$300 parts and labor
- Brake/clutch switch replacement: $75–$200
- Clock spring replacement: $250–$600 (more on some luxury models)
- Wiring/connector repair: $100–$400 depending on severity
- ECU/BCM diagnosis and replacement: $400–$1,200+ (rare for this code)
Costs are affected by vehicle make, parts availability, shop labor rate, and whether other components (like the airbag or steering wheel) must be removed and reinstalled.
Can I Still Drive With P0585?
In most cases, you can still drive with a P0585 code without damaging the engine or transmission. The main downside is that cruise control may not work or may shut off unexpectedly, which can be annoying on long trips. However, if the issue is tied to a brake light switch or wiring fault, you could also have brake light problems or other safety-related issues.
If you notice inconsistent brake lights, an airbag warning, or other electrical oddities, treat the situation more seriously and have it inspected as soon as possible. Avoid long highway drives using cruise until you know the system is reliable.
What Happens If You Ignore P0585?
If you ignore P0585, you’ll likely just live without reliable cruise control, but you may also be ignoring early signs of wiring or switch problems that can spread to other systems. A failing clock spring, for example, can eventually trigger airbag faults or disable steering wheel controls. Addressing the code early often prevents more expensive electrical repairs down the road.
Related Codes
- P0574 – Cruise Control System Vehicle Speed Too High
- P0573 – Brake Switch “A” Circuit High
- P0572 – Brake Switch “A” Circuit Low
- P0571 – Brake Switch “A” Circuit
- P0570 – Cruise Control Accelerate Signal
- P0569 – Cruise Control Coast Signal
- P0568 – Cruise Control Set Signal
- P0567 – Cruise Control Resume Signal
- P0566 – Cruise Control Off Signal
- P0565 – Cruise Control On Signal
Key Takeaways
- P0585 means the ECU is seeing conflicting or incorrect cruise control input signals.
- The engine usually runs fine, but cruise control may not work or may be unreliable.
- Common causes include faulty cruise switches, a bad clock spring, and brake/clutch switch problems.
- Diagnosis involves scan tool data, switch testing, and careful inspection of wiring and the steering column.
- Repairs are typically in the low to mid range cost-wise, unless major wiring or modules are involved.
Vehicles Commonly Affected by P0585
P0585 can show up on many makes, but it’s more frequently seen on vehicles with steering wheel–mounted cruise and audio controls. In the field, I’ve seen this code fairly often on:
- Ford and Lincoln SUVs and trucks (Explorer, F-150, Expedition) with aging clock springs.
- Chevrolet and GMC pickups and SUVs (Silverado, Tahoe, Sierra, Yukon) with worn steering wheel switches.
- Toyota and Lexus sedans and crossovers (Camry, Corolla, Highlander, RX) using stalk-style cruise switches.
- Honda and Acura models (Accord, Civic, CR-V, MDX) where steering wheel controls or brake switches start to fail.
- Volkswagen and Audi vehicles with combination stalks and more complex body control modules.
The exact failure pattern varies by brand, but the diagnostic approach is similar across most modern vehicles.
FAQ
Can I clear P0585 and keep driving without fixing it?
You can clear P0585 with a scan tool, and the light may stay off for a while, but if the underlying problem is still there, the code will usually return. Driving is generally safe, but you’ll likely lose cruise control again and may be ignoring an electrical issue that can get worse over time.
Is P0585 related to the brake lights not working?
It can be. A faulty or misadjusted brake pedal switch can trigger P0585 and also cause brake lights to stay on or not come on at all. If you have both a cruise problem and brake light issues, start by checking and testing the brake switch and its wiring.
How do I know if the clock spring is causing P0585?
Suspect the clock spring if multiple steering wheel functions are intermittent: horn cuts out, radio controls stop working, airbag light comes on, and cruise buttons act up, especially when you turn the wheel. Testing continuity through the clock spring and checking for related airbag codes can confirm the diagnosis.
Can a bad battery or low voltage set P0585?
Low system voltage can cause all kinds of strange electrical behavior, including incorrect readings from cruise control inputs. While a weak battery alone is not the most common cause of P0585, it can contribute. If you’re chasing multiple electrical codes, it’s smart to test battery and charging system health first.
Do I need a dealer to fix a P0585 code?
Not always. Many independent shops and experienced DIYers can handle cruise switch, brake switch, or clock spring replacement using quality parts and proper procedures. You may need a dealer or well-equipped shop if ECU programming, advanced diagnostics, or brand-specific scan tools are required for your particular vehicle.