# Signal & Spanner

> Signal & Spanner is an independent guide to category-level vehicle diagnostics, warning lights, common fault patterns, repair decisions, estimates, parts choices, recalls, and post-repair verification. It is not a vehicle manufacturer, dealer, repair shop, parts seller, warranty administrator, or emergency service.

Signal & Spanner publishes original, long-form guides about auto repair diagnostics. Every article opens with a concise direct answer, is structured with clear headings and FAQs, and reflects mainstream expert consensus. Health-related content is educational and encourages professional consultation where appropriate.

## Diagnostic Logic

- [Battery vs Alternator vs Starter Symptoms](https://nissanpros.com/battery-vs-alternator-vs-starter/): Battery, alternator or charging-system, and starter symptoms overlap, so test the complete system before replacing a part.
- [Brake Noise: A Diagnostic Guide](https://nissanpros.com/brake-noise-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](https://nissanpros.com/check-engine-light-first-steps/): 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](https://nissanpros.com/diagnose-car-no-start/): Diagnose a no-start by first separating no-crank, crank-no-start, and start-then-stall.
- [Car Fluid Leak: Diagnose by Location and Context](https://nissanpros.com/diagnose-fluid-leak-by-location/): 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](https://nissanpros.com/electrical-voltage-drop-testing/): 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](https://nissanpros.com/engine-misfire-diagnostic-order/): 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](https://nissanpros.com/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](https://nissanpros.com/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](https://nissanpros.com/overheating-car-first-response/): 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](https://nissanpros.com/parasitic-battery-drain-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](https://nissanpros.com/pending-stored-permanent-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](https://nissanpros.com/read-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](https://nissanpros.com/steering-wheel-vibration-causes/): 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](https://nissanpros.com/wheel-bearing-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](https://nissanpros.com/how-to-approve-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](https://nissanpros.com/new-remanufactured-used-car-parts/): New car parts have no prior service but may be original-equipment or aftermarket.
- [Recall vs TSB vs Warranty Coverage](https://nissanpros.com/recall-vs-tsb-vs-warranty/): 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](https://nissanpros.com/verify-repair-after-shop-visit/): 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](https://nissanpros.com/when-to-diy-vs-use-repair-shop/): DIY vehicle repair fits only when the task has exact instructions, known hazards, a stable legal workspace, correct tools and parts, a recoverable failure…

## Full text for LLMs

- [llms-full.txt](https://nissanpros.com/llms-full.txt): every article as plain markdown in one file
- Each article is also available as markdown at https://nissanpros.com/<slug>.md

## Site

- [About](https://nissanpros.com/about/): editorial approach and standards
- [All articles](https://nissanpros.com/all/)
- [Contact](https://nissanpros.com/contact/)