Why is my Subaru cruise control not working?
The most common culprits are a faulty brake light switch, a blown fuse, or a failed cruise control actuator. Other electrical or sensor issues can also prevent cruise control from engaging.
This article explores the likely causes, how to diagnose them safely, and when to seek professional help. It covers Subaru models across generations, where cruise control depends on a network of switches, sensors, and electronic control modules to engage and hold a set speed.
Common causes
These are the issues most frequently responsible for cruise control not engaging or losing speed in Subaru models. Checking them in a systematic order can save time and money.
- Faulty brake light switch or brake pedal switch: If the system detects the brakes are pressed or the switch is malfunctioning, it will disable cruise control.
- Blown fuse or relay in the cruise control circuit: A power or control circuit interruption prevents engagement.
- Failed cruise control switch or steering wheel clock spring: A bad stalk control or a damaged clock spring can disrupt the connection to the cruise control module.
- Vacuum hose or actuator problems (older Subaru models): Vacuum leaks or a failing cruise control servo can prevent speed matching.
- Throttle position sensor (TPS) or accelerator pedal position sensor (APPS) issues: If the ECU cannot read the pedal position accurately, cruise may not engage or hold speed.
- Sensor/ECU faults or ABS/stability-control interference: Faulty wheel speed sensors or ABS modules can disable cruise as a safety precaution.
Crucially, cruise control relies on multiple inputs and a reliable power supply. A fault in any one component or a loose connection can stop the system from working. If these checks don’t identify a clear cause, a diagnostic scan is the next best step.
How to diagnose and troubleshoot
Follow these steps to systematically identify the root cause. Start with the simplest checks before moving to more involved diagnostics or repairs.
- Confirm basic eligibility: ensure the vehicle is above the minimum speed threshold and that the cruise control switch is turned on.
- Test the brake lights and brake switch: press the brake pedal and confirm the brake lights illuminate; if they don’t, replace or adjust the brake light switch.
- Check fuses and relays: locate the cruise control-related fuses in the panel and replace any blown fuses.
- Run a diagnostic scan: use an OBD-II scanner to pull trouble codes related to throttle, speed sensors, ABS, or cruise control.
- Inspect the vacuum system (if applicable): for older models, look for cracked hoses or leaks in the cruise control vacuum lines and inspect the actuator.
- Evaluate the throttle and pedal sensors: test or inspect the TPS/APPS readings to ensure correct throttle position data.
- Check wheel speed sensors and ABS components: verify no active fault codes and ensure wheel speeds read correctly on the dash.
- Inspect steering-column wiring: examine the clock spring and cruise control wiring for continuity and damage.
- Test the cruise control actuator and wiring: ensure the actuator is functioning and receiving proper signals from the control module.
Note: Some steps require specialized tools or training. If you’re uncomfortable with electrical diagnostics, it’s safer to consult a qualified technician to avoid issues with braking or airbags.
When to seek professional help
If basic checks don’t restore function or you notice warning lights, seek professional assistance promptly. A technician can pull OEM service data, perform deeper diagnostics, and address recalls or software updates that may affect cruise control.
- Warning lights or diagnostic codes pointing to cruise control, throttle, or ABS systems.
- Persistent failure to engage, even after checking switches, fuses, and simple wiring.
- Suspicion of steering-column issues (clock spring) or damaged wiring harness.
- Recent electrical work, battery disconnections, or recalls that could impact cruise control operation.
A professional inspection can determine whether the issue is a sensor replacement, wiring repair, module update, or a more involved component replacement.
What to expect at the shop
If you take your Subaru in for cruise control problems, technicians typically follow a structured diagnostic path, using vehicle-specific service information and scan tools to verify a fault and identify the faulty component.
Typical diagnostics and repairs
- Electrical system verification: test battery health, charging system, and voltage stability.
- Switch and wiring inspection: check the brake switch, cruise stalk wiring, and clock spring for continuity and damage.
- Control module and sensor tests: scan for codes, inspect the cruise control module, TPS/APPS readings, and wheel speed sensors.
- Actuator/vacuum check: verify the cruise control actuator operation and vacuum lines (if applicable).
- Software updates or recalls: apply any available updates or service bulletins relevant to cruise control.
After diagnosis, the shop will provide an upfront estimate and explain the needed parts and labor. If multiple components are involved, costs can vary, but addressing the root cause generally prevents repeated visits.
Summary
Subaru cruise control not working is most often caused by a faulty brake switch, a blown fuse, or a failing cruise control actuator, but sensor, wiring, or software issues can also block engagement. Start with simple checks—brake lights, fuses, and a basic diagnostic scan—and, if necessary, move to more thorough inspections of the steering column, throttle sensors, and wheel speed sensors. When in doubt, a professional diagnosis ensures safety and helps prevent misdiagnosis or missed recalls.
