Light Index · Mobile Diagnostics · Hill Country TX
A warning light is not a diagnosis — it is one module's decision based on one sensor reading, and the part its icon looks like is often the least likely culprit. Each light below gets the same honest treatment as the symptom guide: the emergency call first, then what it usually proves to be, what a parts-changer will sell you, and the test that settles it.
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A loose or cracked gas cap — the cheapest way this light lies about a $400 problem
A wheel-speed sensor or its tone ring (damaged, corroded, or coated in metallic brake dust)
Seat-buckle switch or its under-seat wiring — coffee, car seats, and seat tracks kill these constantly
Serpentine belt snapped or slipped off — no belt, no alternator, no water pump, no power steering
Low oil level from a leak or consumption — the free answer you check first
Low coolant from a leak — hose, water pump weep hole, radiator, heater core (sweet smell, foggy windows)
Genuinely low pressure — slow leak, cold-weather physics (about 1 psi per 10 degrees F), or a valve stem
A dirty/failing wheel-speed sensor (shared with ABS — the two lights usually come on together)
A range/pressure/speed sensor or solenoid circuit — cheap parts, exact codes, commonly the real story
Red brake lamp with the parking brake off: low fluid or one hydraulic circuit down — check master-cylinder level immediately
Light on and nobody will tell you what it's actually worth fixing? A flat $150 mobile diagnostic scans every module — not just the engine — anywhere in Canyon Lake, San Antonio & Austin, or read a sample report first.
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