Why is the car's small light always on?

[LaClayton]

In the car dashboard, a triangle exclamation mark light that stays on is the TCS (Traction Control System) indicator light. This light has two functions: 1. Reminder: The light turns on to remind the driver to turn off the traction control system; 2. TCS: If this light comes on and stays on while the traction system is activated, it indicates a problem with the TCS. Dashboard warning lights that must be checked: 1. Tire pressure warning light: When there is an issue with tire pressure, the tire warning light will illuminate. The tire pressure of a car is something we need to pay special attention to. If there is a problem with tire pressure, the tire condition must be checked immediately. 2. ABS light: ABS is the Anti-lock Braking System in a car. The anti-lock braking system is related to the safety of driving the vehicle. The ABS indicator light signifies a fault in the anti-lock braking system, which must be inspected promptly. 3. Engine fault indicator light: The engine fault indicator light shows the operating status of the engine, usually in yellow or red. During vehicle self-check, it will light up automatically. It turns off automatically after starting, but if the engine fault indicator light stays on, the engine condition should be checked promptly.

[HenryRose]

I've encountered this situation before and spent a long time troubleshooting. The most common cause is the light control lever not returning to its original position, especially easy to forget after driving at night. Secondly, doors not being fully closed can also trigger the small lights to stay on. This feature is designed for safety, but becomes problematic if the door lock sensor gets stuck. Short circuits are another hidden culprit, particularly in older vehicles where wiring deterioration can lead to grounding issues. Those who've modified their electrical systems should also be cautious, as faulty aftermarket daytime running light control modules may interfere with the original vehicle system. The most troublesome scenario is a malfunctioning body control module, which governs the entire vehicle's lighting logic. In such cases, don't force the vehicle to operate. First check switch positions, disconnect the battery cable as an emergency measure, and promptly visit a repair shop to read the fault codes.

[Leanne]

My car had the same issue last month, with the daytime running lights staying on which was quite unsettling. First, check the light switch near the dashboard to see if it's stuck in the parking light position. Then, test each door switch—the trunk lid is especially easy to overlook, as aging seals can cause poor contact. Another possibility is incorrect wiring from aftermarket installations like dashcams or ambient lighting; I've seen a friend's car with constant light issues due to messy wiring. Also, a stuck remote key button could continuously send a light-on signal. When troubleshooting, remember to use a multimeter to check the voltage at the fuse box. If there's still current 15 minutes after locking the car, it’s likely a parasitic drain issue.

[MacManuel]

Having worked in auto repair for over a decade, I frequently handle such cases. When parking lights stay constantly on, 90% of the time it's an electrical circuit issue: The most common cause is contact adhesion inside the lighting combination switch; another frequent culprit is burnt relays preventing contact separation; water ingress causing door control switch short circuits is also common. In some German cars, short circuits in the footwell light modules can affect the parking light circuit too. For vehicles retrofitted with xenon lights, pay special attention to the ballasts - substandard products can cause reverse power feed. Diagnosis requires using an oscilloscope to check signal waveforms and measuring the BCM module's output terminals. The simplest solution is still taking it to a professional shop to read fault codes - DIY disassembly often leads to broken clips.