P0590 — Cruise Control Multi-Function Input “B” Circuit Stuck #

Note: The code description and naming may vary depending on the vehicle manufacturer (OEM). Below is a list of known label variations for this Diagnostic Trouble Code (DTC):

• Ford: Cruise Control Multi-Function Input “B” Circuit Stuck
• General Motors (GM): Cruise Control Switch “B” Circuit Malfunction
• Toyota: Cruise Control Switch Input “B” Circuit Stuck
• Chrysler: Cruise Control Multi-Function Switch “B” Circuit
• Honda: Cruise Main Switch Input “B” Circuit Stuck

Summary of Code P0590 #

P0590 is a Diagnostic Trouble Code (DTC) that indicates an electrical issue in the cruise control multi-function switch—specifically, the “B” circuit appears to be stuck. The cruise control system allows a driver to maintain a set speed without keeping their foot on the accelerator, using a combination of switches typically found on the steering wheel or column. When the Engine Control Module (ECM) or Powertrain Control Module (PCM) detects that one of these switches (the “B” input, often related to coast, set, or cancel functions) is not responding as expected—usually stuck in either the on or off position—it will trigger the P0590 code. This can cause the cruise control to become inoperable or behave unpredictably. The issue often points to an electrical fault rather than a mechanical one, though both should be considered during diagnosis.

Frequent Symptoms for Code P0590 #

Drivers or technicians encountering code P0590 will typically notice issues directly related to the cruise control system. The most common symptoms are often subtle until the cruise control is used. Be on the lookout for the following:

• Cruise control fails to engage or activate
• Cruise control unexpectedly disengages during operation
• Warning light for cruise control or check engine light may illuminate
• Cruise switch feels stuck or unresponsive when pressed
• No response to certain cruise control functions (e.g., coast, set, or cancel)

Probable Causes for Code P0590 #

Code P0590 is generally triggered by an electrical or switch-related problem. The “B” circuit refers to a specific input wire or contact in the multi-function cruise switch assembly. Below are the most frequent causes, ordered by likelihood:

1. Faulty cruise control multi-function switch (switch contacts stuck or failed internally)
2. Damaged or corroded wiring/connectors in the cruise control switch circuit
3. Open or short circuit in the “B” switch input wire
4. Faulty clock spring (rotary electrical connector in the steering wheel)
5. PCM/ECM software errors (rare, but possible if all hardware checks out)

Step-by-Step Diagnostic for Code P0590 #

Diagnosing P0590 requires a systematic approach to avoid unnecessary part replacement and ensure the true fault is found. Follow these steps:

• Verify the code using a scan tool and note any related codes.
• Check cruise control operation—test all switch functions (set, coast, resume, cancel) for responsiveness.
• Inspect the cruise switch for physical sticking or damage (press each button and listen/feel for normal operation).
• Visually examine wiring and connectors from the switch to the clock spring and down to the PCM/ECM for corrosion, fraying, or loose pins.
• Test the clock spring for continuity if the switch is on the steering wheel—this component can develop internal breaks or shorts.
• Check the voltage and resistance at the “B” circuit using a multimeter according to the OEM wiring diagram.
• Clear the code and road test the vehicle to confirm if the issue recurs after any repairs or adjustments.

Possible Repairs for Code P0590 #

Once the root cause is identified, repairs for P0590 should directly address the source of the problem. Here are the most common solutions:

• Replace the cruise control multi-function switch if it is found faulty or physically stuck.
• Repair or replace damaged/corroded wiring or connectors in the “B” circuit.
• Replace the clock spring assembly if continuity is lost or a short is present.
• Re-flash or update the PCM/ECM software if a manufacturer Technical Service Bulletin (TSB) applies.

Can You Drive with Code P0590? #

Yes, you can generally continue to drive with code P0590 because it only affects the cruise control system, not critical engine or safety functions. However, cruise control will likely be disabled or unreliable. If you rely on cruise control for long trips, prompt repair is recommended. Always ensure the switch is not physically stuck in a way that might interfere with other steering wheel functions.

Vehicles Most Commonly Affected by Code P0590 #

While P0590 can appear on any vehicle equipped with cruise control and multi-function steering switches, it is more frequently reported in certain models and brands. This list includes, but is not limited to:

• Ford F-Series trucks (F-150, F-250)
• Chevrolet Silverado and GMC Sierra
• Toyota Camry and Corolla
• Honda Accord and Civic
• Chrysler/Dodge minivans and sedans
• Hyundai Sonata and Elantra

Common Mistakes & Best Practices for Code P0590 #

When diagnosing and repairing P0590, certain pitfalls and oversights are common. Here is how to avoid them and ensure a solid repair:

• Do not replace the cruise control switch without first checking wiring and connectors. Many issues are due to simple electrical faults.
• Avoid skipping the clock spring check—this hidden component is often overlooked but frequently fails.
• Always use the correct wiring diagram for your specific vehicle to avoid misdiagnosis.
• Clear codes and verify repair with a road test before returning the vehicle to service.

Express FAQ for Code P0590 #

Here are quick answers to the most common questions about DTC P0590:

• Q: Will P0590 trigger a check engine light?
  A: Sometimes. It depends on the vehicle, but usually the cruise control warning light or message will appear. The check engine light may also illuminate in some models.
• Q: Can a DIYer fix P0590 at home?
  A: Often, yes—if you are comfortable with basic electrical testing and have access to a wiring diagram. However, steering wheel airbag safety precautions are essential when accessing the switch or clock spring.