All articles
Everything on Signal & Spanner, organised by topic.
Diagnostic Logic
- Battery vs Alternator vs Starter Symptoms — Battery, alternator or charging-system, and starter symptoms overlap, so test the complete system before replacing a part.
- Brake Noise: A Diagnostic Guide — Treat brake noise as a safety complaint: stop and tow for reduced braking, abnormal pedal, pulling, smoke, hot wheel, leaks, warnings, severe vibration,…
- Check Engine Light: What to Do First — When a check-engine light appears, identify the exact symbol in the vehicle manual and record whether it is steady or flashing plus every symptom and…
- Car Won't Start: A Safe Diagnostic Order — Diagnose a no-start by first separating no-crank, crank-no-start, and start-then-stall.
- Car Fluid Leak: Diagnose by Location and Context — Treat a vehicle fluid leak as unknown. Keep people and animals away; record parking position, time, weather, air-conditioning use, service, warnings,…
- Voltage-Drop Testing Without Chasing Ghosts — Automotive voltage-drop testing measures voltage consumed across a circuit section while current flows, revealing resistance an unloaded continuity check…
- Engine Misfire: Diagnose Before Replacing Parts — Diagnose an engine misfire by recording when it occurs, saving code statuses, freeze-frame data, counters, temperatures, fuel-control information, and…
- OBD Freeze-Frame Data Explained — OBD freeze-frame data is a saved selection of operating values from around the time an emissions-related fault met its storage logic.
- OBD Readiness Monitors Explained — OBD readiness monitors show whether applicable emissions self-tests have completed since a reset or relevant event.
- Car Overheating: Stop Conditions and Next Steps — When a car overheats, pull over safely and follow the vehicle manual; stop immediately for steam, coolant discharge, power loss, oil-pressure warning,…
- Parasitic Battery Drain Diagnosis Basics — Diagnose parasitic battery drain only after charging and testing the correct battery, verifying connections and charging performance, and proving excess…
- Pending vs Stored vs Permanent Trouble Codes — A pending code generally records an initial detected condition that has not yet met the criteria to mature.
- How to Read an OBD2 Code Without Guessing — Read an OBD2 code as evidence of a detected system or circuit condition, not proof that the component named in its description has failed.
- Steering-Wheel Vibration: Sort the Clues — Sort steering-wheel vibration by when it occurs: road speed, braking, acceleration, turning, bumps, or engine speed while stationary.
- Wheel-Bearing Noise vs Tire Noise — Distinguish wheel-bearing noise from tire noise by recording how the hum, roar, or growl changes with speed, road surface, temperature, braking, gentle…
Repair Decisions
- How to Approve an Auto Repair Estimate — Approve an auto repair estimate only after it identifies the symptom, diagnostic scope and fee, evidence, proposed correction, parts class, anticipated…
- New vs Remanufactured vs Used Car Parts — New car parts have no prior service but may be original-equipment or aftermarket.
- Recall vs TSB vs Warranty Coverage — A safety recall is a formal remedy for an affected safety defect or noncompliance; check the exact VIN and follow interim instructions.
- How to Verify a Car Repair After the Shop — Verify a car repair by comparing the completed order with estimates and approvals, confirming the complaint, diagnosis, parts class, labor, charges,…
- DIY Car Repair vs a Shop: Draw the Safety Line — DIY vehicle repair fits only when the task has exact instructions, known hazards, a stable legal workspace, correct tools and parts, a recoverable failure…