Flickering Headlights & Intermittent Cruise Control on 2016 Impreza

ClearTheCode admin answer:

Flickering headlights and intermittent cruise control, especially without dashboard warning lights, can indeed be related and often point to a common power supply issue or a problem within the vehicle's electrical network.

Causes:

• Weak Alternator/Voltage Regulator: An alternator that isn't consistently providing stable voltage can cause flickering lights and affect other voltage-sensitive electronics like cruise control.
• Weak or Failing Battery: While the car starts, a battery that can't hold a stable charge can lead to voltage fluctuations.
• Loose or Corroded Ground Connections: Poor grounding points for the engine or chassis can cause a wide array of intermittent electrical gremlins throughout the vehicle.
• Faulty Headlight Switch/Wiring: Less likely to affect cruise control, but a failing switch or wiring could cause the flickering.
• Steering Wheel Clock Spring: The clock spring allows electrical connections (for airbags, horn, cruise control buttons) to pass from the steering column to the wheel while it turns. A failing clock spring can cause intermittent issues with steering wheel controls, including cruise control.

Diagnostic Steps:

1. Battery and Alternator Test: Have your battery and alternator professionally tested. Many auto parts stores offer this service for free. A weak battery or an alternator not consistently providing stable voltage is a prime suspect.
2. Check Ground Connections: Visually inspect the main engine and chassis ground points for any signs of corrosion or looseness. Clean and tighten them if necessary.
3. Inspect Headlight Connections: Check the wiring harnesses and bulbs for the headlights for any visible damage or loose connections.
4. Steering Wheel Control Check: If other steering wheel controls (like the horn or audio buttons) also act up intermittently, it strengthens the case for a failing clock spring.

Common OBD Codes:

• For these specific symptoms, generic OBD-II codes are unlikely. However, a shop's advanced scanner might pull B-codes (Body Control Module) or U-codes (communication network) if a module is malfunctioning or if there are communication errors between systems.

When to See a Shop: If your battery/alternator tests are inconclusive, or if you're uncomfortable checking electrical connections and grounds, it's advisable to visit a professional. Intermittent electrical issues can be challenging to diagnose, and a shop can use specialized diagnostic tools to monitor voltage stability across various circuits and check for stored fault codes that might not trigger a dashboard warning light.