How to test a cruise control module?

To test a cruise control module, start with a diagnostic readout to pull fault codes, verify power and grounds, and confirm sensor inputs and actuator response. If the module receives proper inputs but cannot command throttle, the issue likely lies with the CCM, actuator, or wiring. This guide covers both traditional vacuum-based systems and modern drive-by-wire setups.

Cruise control modules manage throttle position to maintain a chosen speed. Testing them involves electrical checks, sensor data verification, and actuator testing. Depending on the vehicle, the CCM may be a separate unit or integrated with the engine control module (ECM) or ABS/TC module. Procedures vary by manufacturer, so always consult the factory service information for your specific model.

Electrical and sensor diagnostics

Before you start the electrical and sensor tests, ensure the vehicle is safely parked and the area is secure. Use an OBD-II scanner capable of live data to read CCM-related codes and monitor real-time data while attempting to engage cruise.

1. Connect an OBD-II scanner with live data for cruise control diagnostics. Retrieve stored or pending codes and observe live signals for cruise enable status, set speed, brake switch, vehicle speed signal, and throttle/pedal inputs.


2. Check power and ground at the cruise control module harness. With ignition on, verify a steady 12V supply on the CCM power pin(s) and a solid ground on the ground pin(s). Inspect fuses and wiring for corrosion, damage, or loose connections.


3. Verify input signals required to enable cruise. This typically includes the brake pedal switch, clutch switch (for manual transmissions), cruise enable/ON switch or stalk, and accelerator pedal position (APP) input. Confirm these signals are present and change as you operate the controls or pedals.


4. Assess the vehicle speed input. The speed signal (VSS or wheel-speed sensor data) should be present and consistent with the actual vehicle speed. Compare scanner-reported speed to the speedometer reading at a known speed or by safe, controlled testing.


5. Check throttle-related sensors. For drive-by-wire systems, verify the accelerator pedal position sensor and electronic throttle control position. For older systems, verify the throttle position sensor and its wiring, ensuring proper correlation with pedal input.


6. Inspect wiring and connectors for damage. Look for cracked or corroded pins, moisture ingress, or loose connectors at the CCM and related sensor connections. Re-seat connectors and clean as needed.

Electrical and sensor checks determine whether the CCM receives correct inputs and can issue proper throttle commands. If data shows correct signals but the cruise control does not engage or hold speed, the module or actuator may be defective, or there may be a wiring fault.

Actuator and system operation

Activation and throttle control must be tested in a controlled environment. For traditional vacuum-based cruise control, inspect the vacuum lines and actuator; for electronic throttle control, test the throttle motor and its control circuitry. Always follow vehicle-specific procedures to avoid engine damage or safety risks.

1. Inspect the vacuum system (for traditional vacuum cruise control). Check all hoses for cracks, splits, or loose connections. Test the vacuum supply with a gauge if available and ensure the vacuum reservoir is in good condition. A loss of vacuum often causes cruise failure.


2. Test the cruise control actuator/solenoid. In vacuum systems, verify the actuator receives vacuum when cruise is commanded to engage. In drive-by-wire systems, observe the throttle motor position and current draw while the cruise is active via the scan tool. Look for abnormal movement, stalling, or excessive current draw.


3. Perform a commanded throttle test. Using the scan tool or service connector, enable cruise and command a target speed. Observe whether the actuator moves to the expected throttle position and whether the vehicle maintains the commanded speed. If the throttle does not move or responds erratically, the actuator or its control circuit may be faulty.


4. Check for mechanical binding. Ensure there is no binding in the throttle linkage, idle air control, or throttle body that could prevent proper throttle movement even when the CCM commands a position.


5. Rule out other engine controls. A misfire, improper idle speed, or lean/rich condition can prevent cruise control from maintaining speed. Verify ignition, fueling, and idle control systems are within specification before concluding CCM-related faults.

Note: Vehicle-specific configurations vary widely. Some cars use a combined CCM within the ECM or ABS/TC module, and some systems require manufacturer-specific diagnostic tools or service procedures. Do not bypass safety features or attempt dealer-only workflows unless you have authorized access to the correct tooling and procedures.

Vehicle-specific notes

For modern vehicles with drive-by-wire throttle and integrated control systems, a factory-level diagnostic tool (or a supported equivalent) may be required to access certain CCM functions, run actuator tests, or command the throttle in a controlled manner. If a comprehensive test cannot be completed with generic tools, consult the vehicle’s service information or a qualified technician.

Summary

Testing a cruise control module involves a two-pronged approach: first, verify electrical power, grounds, and input signals ( brake, enable, speed sensor, pedal position), using an OBD-II scanner for fault codes and live data; second, test the actuator and throttle control—whether vacuum-based or electronic drive-by-wire—by commanding the system and observing throttle response. If signals are correct but the system won’t engage or hold speed, the CCM, actuator, or the wiring between them is likely at fault. When in doubt, especially on newer vehicles, rely on manufacturer-specific guidance and professional diagnostic tools.

What module controls the cruise control?

The E-Cruise Module is the proverbial "brain" of the entire system and with the assistance of the included accelerator pedal interface harness, intercepts the communication between the pedal position sensor and the vehicle' Electronic Control Unit (ECU).

How to test if cruise control is working?

You can tell if cruise control is on by checking your dashboard for an indicator light, which often changes from white or amber to green when the speed is successfully set. The icon typically looks like a speedometer, sometimes with a car symbol or chevrons in front of it, and will show a "Set" indicator when the speed is locked in. 
This video demonstrates how to check cruise control indicators on a car's dashboard: 57sEden Motor GroupYouTube · Sep 5, 2023
Dashboard indicator light 

• "Main" or "On" light: A "main" or "cruise" light will usually turn on to show the system is powered on, but this does not mean a speed has been set. 
• "Active" light: The light will often turn green to indicate that cruise control is active and set at the current speed. 
• Other colors: A white or amber light can mean the system is on and ready, but not yet active. 

Steering wheel or stalk controls 

• On/Off button: First, press the "On" or "Cruise" button to power the system. A corresponding symbol will appear on the dashboard. 
• Set button: While at your desired speed, press "Set." A "Set" indicator or the main light will change to confirm the speed is locked in. 

Other clues

• Engine speed: When cruise control is active, your engine will maintain a steady speed, and you will not need to use the accelerator pedal. 
• Speed display: Some systems show the set speed on the dashboard or a head-up display. 
• Adaptive cruise control: This advanced system may show a symbol with a car and chevrons, and will adjust your following distance based on the vehicle ahead. 

What is the most common failure of a cruise control system?

The most common failures in a cruise control system are often due to a faulty brake light switch or a blown fuse, according to several sources. Other frequent issues include problems with the speed sensor, a loose or broken cruise control cable, and general electrical or vacuum leaks. 
Common failure points

• Faulty brake light switch: This is a very common cause of failure. A defective switch can signal to the system that the brake is being applied, causing the cruise control to disengage. 
• Blown fuse: Cruise control systems are protected by fuses, and if a fuse blows, the system will stop working. This is a simple and inexpensive fix, so it's a good first thing to check. 
• Damaged speed sensor: The speed sensor is critical for providing the system with accurate vehicle speed information. If it's damaged, the cruise control won't function correctly. 
• Broken or loose cruise control cable: The cable that connects the system to the throttle can become damaged or loose, preventing the system from working properly. 
• Electrical issues: Since cruise control is an electrical system, other problems like faulty wiring, a bad cruise control switch on the steering wheel, or a malfunctioning vacuum-actuated switch can cause it to fail. 

Other potential causes

• Traction control system: If the car's anti-lock braking (ABS) or traction control systems are not functioning properly, they will often disable cruise control as a safety measure. 
• Dashboard warning lights: A "check engine" light or other dashboard warnings can also disable the system. 
• Adaptive cruise control sensors: For modern adaptive systems, external factors like bad weather, a dirty windshield, or a blocked radar sensor can cause the system to deactivate.