Vehicle Troubleshooting

An AI skill for symptom-first diagnosis — noises, vibrations, smells, leaks, warning lights, and drivability problems — using structured differential diagnosis to narrow causes before any parts are bought.

Description

Vehicle Troubleshooting starts where the OBD-II scanner cannot help: “it makes a clunk over bumps,” “it smells like syrup,” “it pulls left when braking.” The skill applies a differential-diagnosis approach — gather the symptom’s full signature (when, where, under what conditions), rank probable causes, and propose discriminating tests that split the possibilities fastest and cheapest.

Audience: Any driver experiencing a problem, and technicians who want a structured second opinion.

Capabilities

• Diagnose by symptom category:
  • Noises — squeal, grind, clunk, knock, hum, whine, tick, hiss; correlated with speed, RPM, steering, braking, or bumps
  • Vibrations — by speed range, under acceleration/braking/coasting, through wheel/seat/pedal
  • Smells — burning oil, coolant (sweet), fuel, sulfur, burnt clutch/brakes, mildew
  • Leaks — identify fluid by color, texture, and location under the vehicle
  • Warning lights — meaning, severity, and safe-to-drive assessment
  • Drivability — hard start, no start, stalling, rough idle, hesitation, poor fuel economy, overheating
  • Electrical — battery drain, dim lights, intermittent accessories, no-crank vs. no-start
• Ask targeted follow-up questions that discriminate between causes
• Rank causes by probability for the specific vehicle and mileage
• Propose the cheapest/fastest test that eliminates the most possibilities
• Give an urgency verdict: stop driving now / drive gently to a shop / monitor / cosmetic
• Explain how to safely reproduce and characterize a symptom for diagnosis

Example Prompts

My 2016 Ford Escape makes a rhythmic humming noise above 40 mph that gets
louder in right-hand curves. What is it likely to be?

Car cranks strongly but won't start after sitting overnight. Starts fine
when warm. 2010 VW Golf 2.5. Where do I start?

There's a puddle of orange-pink fluid under the front of my car near the
passenger side. What is it and how urgent is this?

Steering wheel shakes between 60-70 mph only, smooth above and below.
What does that speed-specific pattern tell you?

Battery dies if the car sits for 3 days. Battery and alternator both test
good. How do I find a parasitic drain?

Recommended Workflow

For model-specific checks, follow reference routing using the variant, production year, and original market. The browser builder can prepare the prompt. A reference match does not establish a fault, eligibility, or completion.

Standalone installation: If the repository-relative routing guide or data files are missing, use the online routing guide or browser builder. Ask for the exact variant, production year and original market; inspect the full reference and current official sources. If the resources cannot be accessed or no profile matches, say model-specific evidence is unavailable and continue only with general guidance. A match is not a diagnosis, recall eligibility, or proof of completion.

1. Describe the symptom’s full signature. What you sense, when it started, whether it is constant or intermittent, and what conditions trigger it (speed, RPM, temperature, steering, braking, weather).
2. Answer the follow-up questions. The discriminating details (“does it change when you press the clutch?”) are what narrow the diagnosis.
3. Get the ranked differential. Ask for causes ordered by probability, with an urgency verdict.
4. Run the discriminating tests. Do the suggested checks and report results — each answer prunes the list.
5. Confirm before buying parts. Ask “what test confirms this is the cause?” before spending money.
6. Hand off to repair. Once confirmed, use the Mechanic Assistant for the fix, or take the confirmed diagnosis to a shop.

Limitations

• Diagnosis by description is probabilistic. Sounds and sensations are hard to describe precisely; the assistant gives likelihoods, not certainties.
• Safety overrides diagnosis. Brake failure symptoms, steering problems, fuel smells, and overheating warrant stopping the vehicle first and diagnosing second.
• Intermittent faults may need data logging or professional equipment (oscilloscope, chassis ears, smoke machine) to pin down.
• Cannot hear audio or view video in most clients — describe the symptom, or use character of the sound (frequency, rhythm, correlation).
• Some symptom patterns are vehicle-specific in ways general reasoning misses; model-specific forums and TSBs remain valuable cross-checks.

Related Skills

• OBD-II Diagnostic Assistant — when a warning light or stored code accompanies the symptom
• Mechanic Assistant — executing the repair after diagnosis
• Motorcycle Mechanic — two-wheeled troubleshooting
• Service Intake Assistant — prepare a factual workshop handoff