Why is my check engine light on and cruise control not working?
Typically, a lit check engine light along with a cruise control that won’t engage means the car’s computer has detected a fault and has disabled the cruise function as a safety precaution. The root cause is usually an engine or emissions issue rather than a problem with the cruise control system itself.
Understanding the signal: what the check engine light means
How the MIL is triggered
The check engine light, officially known as the Malfunction Indicator Lamp (MIL), lights up when the engine computer (ECU) has detected a fault in the engine, transmission, or emissions controls. It stores diagnostic trouble codes (DTCs) that point to the general area of concern. A flashing MIL typically signals a more urgent condition (like a misfire) than a steady light.
Interpreting the codes and what they tell you
Codes range from generic to manufacturer-specific. Reading the codes with an OBD-II scanner helps identify whether the issue is related to ignition, fuel delivery, sensors, or emissions equipment. Professional diagnosis is often needed to translate the codes into exact repairs and to determine whether the issue affects cruise control operation.
Common fault categories that trigger a CEL include misfires, sensor faults, vacuum leaks, and issues with the fuel or exhaust systems. The following list highlights typical causes you might encounter.
- Engine misfire or rough running (spark plugs, ignition coils, wiring)
- Faulty or contaminated oxygen (O2) sensors or catalytic converter issues
- Mass airflow (MAF) sensor problems or vacuum leaks
- Faulty throttle position sensor (TPS) or throttle body
- Evaporative system leak or a loose or missing gas cap
- Fuel delivery problems (weak fuel pump, clogged filter, dirty injectors)
- Electrical faults in the engine control module or wiring harness
- Transmission sensors or related faults that affect engine performance
In short, when you see these issues, it’s a sign you should get a diagnostic check to read the codes and address the root cause promptly rather than driving long distances with an unresolved fault.
Why cruise control stops working when the CEL is on
Link between engine faults and the cruise control system
Cruise control relies on accurate engine and vehicle sensor data. If the ECU detects a fault, it may automatically disable cruise to prevent accelerating a malfunctioning engine or driving with compromised emissions controls. Many vehicles also disable cruise if there is a safety-related fault in the brake system or related sensors.
The most common reasons cruise control stops functioning in conjunction with a CEL include the following:
- Engine misfire or rough running that affects throttle response
- Brake pedal switch or brake system fault that prevents safe use of cruise
- Vehicle speed sensor or other speed data issues used by the cruise control system
- Transmission or ECU faults that trigger a safe-mode condition
Note that some faults may not directly cause the CEL but can still disable cruise control as a precaution. If the MIL is on, treat the vehicle as needing diagnosis before relying on cruise control.
What to do now: steps to diagnose and secure your vehicle
Safety and initial checks
Before diving into repairs, consider basic checks and safety steps. If the MIL is flashing, stop driving and seek immediate professional help. If it is steady, you can perform some low-risk checks but avoid driving aggressively or long distances until a diagnostic is performed.
To move from symptoms to a plan, follow these practical steps. The following list provides a structured approach you can take, recognizing that a professional diagnosis is often necessary to confirm the exact cause.
- Read the trouble codes with an OBD-II scanner. If you don’t own one, many auto parts stores offer free scans and can print the codes for you.
- Check for obvious, low-cost fixes first, such as ensuring the gas cap is present and properly tightened, and inspecting for obvious vacuum leaks or loose hoses.
- Note any driving symptoms (misfires, rough idle, stalling, power loss) and the conditions under which the CEL lights up (on start, while accelerating, under load).
- Have a professional diagnose and repair using the stored codes and a thorough inspection. Relying only on codes without a hands-on check can lead to incorrect or incomplete repairs.
After you’ve retrieved the codes and performed any safe preliminary checks, schedule a professional diagnosis. A trained technician can perform a more comprehensive inspection, including sensor tests, wiring checks, and, if needed, component replacement.
Summary
A persistent check engine light paired with a non-working cruise control typically signals an engine or emissions fault that has prompted the vehicle to disable cruise for safety. Start by pulling the diagnostic trouble codes, review common culprits like misfires or sensor faults, and address the underlying issue with professional assistance as needed. Prompt diagnosis helps prevent further engine damage and increases the likelihood that normal cruise functionality will return once repairs are completed.
Does cruise control affect your engine?
“It is definitely good for your vehicle and is highly advised especially for long trips,” he shared. Not only does cruise control help to moderate the temperature of your engine, it helps with fuel economy. Some studies have found that you can save up to 10% on your gas budget every year simply by using cruise control.
How do I know if my cruise control fuse is blown?
There are two places on the back side of each fuse to probe; if the test light does not light on both sides of the fuse you will find that the fuse is most likely blown. If the test light does not light on either side of the fuse; you will need to look in the owner's manual to see what that circuit feeds.
What is the main cause of cruise control not working?
Common reasons for cruise control not working include a blown fuse, a faulty brake light switch, or a bad speed sensor. Other issues can be related to electrical problems, such as damaged wiring or a faulty cruise control switch, or a Check Engine light being on. For adaptive cruise control, a dirty camera or sensors can also be the cause.
You can watch this video to learn about the common reasons why cruise control might not be working: 58sMaxTheCarGuyYouTube · Feb 24, 2025
Common causes
- Blown fuse: A blown fuse will interrupt the electrical current to the cruise control system, preventing it from working.
- Faulty brake light switch: The cruise control system is designed to disengage when you press the brake pedal. A faulty switch can send a continuous "brake" signal, or the cruise control may not work if it can't detect the brake pedal being pressed.
- Bad speed sensor: The speed sensor provides information to the cruise control system. If it malfunctions, the system will stop working because it doesn't have accurate speed data.
- Electrical issues: Damaged or loose wiring, or a faulty cruise control switch on the steering wheel, can prevent signals from being sent correctly, as can a problem with the vehicle's main computer or electronic control module.
- Check Engine light is on: A problem with the engine or a related system will often automatically disable the cruise control as a safety precaution.
- Dirty or blocked camera/sensors (Adaptive Cruise Control): If you have adaptive cruise control, dirt or obstructions on the front-facing camera or radar sensors can prevent the system from working correctly.
- Vacuum leak (older vehicles): Some older cars use a vacuum-operated system. A leak in this system can cause the cruise control to fail.
This video demonstrates how to check the brake light switch: 57sAuto Repair GuysYouTube · Oct 7, 2019
How expensive is it to fix cruise control?
The cost to fix cruise control varies widely, from about $150 to $400 for minor issues like a switch or vacuum leak to over $2,000 for major problems like replacing an Adaptive Cruise Control (ACC) radar sensor, which can cost $500 to $1,500 or more for the part plus labor. Factors like the car's make and model, the specific problem, and the type of cruise control system significantly influence the final price.
Cost breakdown by issue
- Minor repairs: If the problem is a simple one, such as a faulty brake switch or a minor vacuum leak, the cost is typically between $150 and $400.
- Component replacement: Replacing a specific part like a cruise control switch or cable can range from under $20 to several hundred dollars for the part alone, plus labor. The total cost depends on the part's price and local labor rates.
- Advanced system repairs: For modern Adaptive Cruise Control (ACC) systems, repairs can be much more expensive. Replacing a radar sensor could cost anywhere from $500 to $1,500 or more, and may require additional calibration, which can add $100 to $200.
- Major malfunctions: For complex issues or older cars with mechanical components, costs can exceed $500, particularly for luxury or foreign cars.
Factors that affect the price
- Car's make and model: Newer, more complex, or luxury vehicles often have higher repair costs than older or less expensive models.
- Type of system: The complexity of your car's cruise control system is a major factor. A simple mechanical system will be cheaper to fix than an electronic one, especially an advanced ACC system that uses radar or cameras.
- Part needed: The specific part that needs replacement—from a simple switch to a complex sensor—will have a significant impact on the total price.
- Labor rates: Shop and dealer labor rates vary by location and the complexity of the repair. An hourly rate can range from $100 to $200, with a repair taking a couple of hours.
What you can do
- Get a diagnostic check: The first step is to have a professional mechanic diagnose the exact problem to determine the scope of the repair.
- Request a detailed quote: Ask for a specific quote for the parts and labor before authorizing any work to be done.
- Compare options: Compare prices between dealerships and independent mechanics. You can also research the cost of parts yourself to see if it's cheaper to purchase them and have an independent mechanic install them.
