🔍 Diagnostic Techniques

Diagnostic Questioning Guide

Master systematic diagnostic questioning to improve first-fix rates and arrive prepared for every job. Professional fault diagnosis techniques for mobile mechanics.

🔍 Diagnostic Mastery ⏱️ 18 min read 📅 Updated: January 2026

🎯 Diagnostic Framework

📊 Methodology 🚗 Vehicle Basics 🔍 Symptom Analysis ⚙️ System Questioning 📱 Technology Integration 🛠️ Job Preparation

📊 Systematic Diagnostic Methodology

Structured approach to vehicle fault diagnosis through systematic questioning

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The SOARIC Method

Proven diagnostic questioning framework used by professional mechanics.

S
SYMPTOMS

What exactly is happening? When does it occur?

O
ONSET

When did the problem first start? Sudden or gradual?

A
ASSOCIATED

Any other symptoms or warning signs?

R
RECENT

Recent services, repairs, or maintenance?

I
INTERMITTENT

Consistent problem or comes and goes?

C
CONDITIONS

What conditions trigger the problem?

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Diagnostic Question Types

Different questioning techniques for gathering diagnostic information.

Open-Ended Questions

AI: "Can you describe exactly what happens when you try to start the car?" Customer: "It makes a clicking sound and the lights dim"

Closed Questions

AI: "Does the clicking happen every time you turn the key?" Customer: "Yes, every single time"

Leading Questions

AI: "From what you're describing, it sounds like it could be the battery or starter motor.When did you last have the battery tested?"
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Question Sequencing

Start with open questions to gather broad information, then use closed questions to clarify specific details.

🚗 Essential Vehicle Information

Critical vehicle data needed for accurate diagnosis and parts preparation

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Vehicle Identification

Essential vehicle information for every diagnosis.

Vehicle Data Checklist

Make, model, and year of manufacture
Engine size and fuel type (petrol/diesel)
Transmission type (manual/automatic)
Current mileage reading
Registration number for parts lookup
Any modifications or aftermarket parts

Smart Vehicle Data Questions

AI: "To help our mechanic prepare, I need some vehicle details.What's the make and model?" Customer: "It's a Ford Focus" AI: "Great, and what year is it? Also, is it petrol or diesel?" Customer: "2019, petrol engine" AI: "Perfect.What's the current mileage showing?"
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Service History Capture

Understanding maintenance history helps narrow diagnostic focus.

Key Service Questions

  • When was the last full service completed?
  • Any recent repairs or replacement parts?
  • Has the vehicle had any recalls addressed?
  • Any ongoing maintenance issues or concerns?
  • Regular servicing schedule being followed?
  • Any warranty work in the last 12 months?

Service History Script

AI: "When did you last have the car serviced or any work done on it?" Customer: "Had the brakes done about 2 months ago" AI: "That's helpful.Was that just brake pads or did they do any other work at the same time?"
Recent Work Potential Connection Follow-up Questions
Brake work Brake noise, pulling, warning lights Any brake pedal changes?
Battery replacement Electrical issues, radio reset Any electrical problems since?
Oil change Engine performance, leaks Any leaks or oil consumption?
Tyre replacement Handling, noise, vibration Any steering or road noise?

🔍 Systematic Symptom Analysis

Detailed questioning techniques for common vehicle symptoms and faults

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Starting Problems

Most common callout - systematic approach to starting issues.

Starting Problem Decision Tree

1
Engine Turn Over?

Does the engine crank when you turn the key?

2
If NO - Electrical Check

Do lights work? Any clicking sounds? Dashboard lit up?

3
If YES - Fuel/Ignition

How much fuel? Any unusual sounds when cranking?

Starting Problems Script

AI: "Let's work through this step by step.When you turn the key, does the engine try to turn over or is there no response at all?" Customer: "It just clicks and the lights go dim" AI: "That clicking with dimming lights usually indicates a battery issue.When did you last drive the car, and have you noticed any electrical problems recently?"
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Warning Light Analysis

Systematic approach to dashboard warning lights.

Warning Light Categories

  • Red Lights: Stop immediately - safety critical
  • Amber/Orange: Caution - service needed soon
  • Blue/Green: Information - system status

Warning Light Questions

AI: "You mentioned a warning light.Can you describe what it looks like? Is it red, orange, or another colour?" Customer: "It's orange and looks like an engine" AI: "That's the engine management light.Is it staying on constantly or does it flash? Also, have you noticed any change in how the engine runs?"
Warning Light Urgency Key Questions
Engine Management (Orange Engine) Medium Performance changes? Fuel consumption?
Oil Pressure (Red Oil Can) Critical Engine noise? Recent oil change?
Coolant Temperature (Red Thermometer) Critical Steam visible? Coolant level?
Brake Warning (Red Circle with ! ) Critical Brake pedal feel? Handbrake on?

⚙️ System-Specific Diagnostic Questions

Targeted questioning for different vehicle systems and components

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Engine Performance Issues

Detailed questioning for engine-related problems.

Engine Performance Questions

  • Does it happen at idle, during acceleration, or both?
  • Any unusual sounds - knocking, rattling, or squealing?
  • How is the fuel consumption compared to normal?
  • Any visible smoke from the exhaust? What colour?
  • Does the engine feel rough or smooth when idling?
  • Any loss of power when accelerating?

Engine Problem Script

AI: "You mentioned the engine doesn't feel right.Can you describe when you notice it most - when starting up, at traffic lights, or when driving?" Customer: "Mainly when I'm accelerating, it feels sluggish" AI: "That's helpful.Is there any black or blue smoke from the exhaust when you accelerate? And how's the fuel consumption - using more petrol than usual?"
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Brake System Diagnosis

Safety-critical brake system questioning.

Brake Safety Questions

  • How does the brake pedal feel - soft, hard, or spongy?
  • Does the pedal travel further than usual?
  • Any grinding, squealing, or unusual brake noises?
  • Does the car pull to one side when braking?
  • Any vibration through the brake pedal or steering?
  • Warning lights showing on the dashboard?
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Brake Safety Protocol

Any brake safety concerns require immediate attention. Advise customer to drive carefully and avoid heavy braking until mechanic arrival.

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Electrical System Issues

Comprehensive electrical fault diagnosis.

Electrical Diagnostic Questions

  • Which specific electrical components aren't working?
  • Did the problem happen suddenly or gradually?
  • Any recent electrical work or modifications?
  • Do the lights dim when using other electrical items?
  • Any burning smells or unusual sounds?
  • Does the problem occur with engine on or off?

Electrical Problem Script

AI: "You mentioned electrical problems.Let's start with the basics - are the headlights and indicators working normally?" Customer: "The headlights are dim and the radio keeps cutting out" AI: "That combination suggests a charging system issue.When you're driving, do you notice if the lights get brighter when you rev the engine?"
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Transmission Problems

Manual and automatic transmission diagnosis.

Manual Transmission Questions

  • Difficulty selecting gears or gear jumping out?
  • Clutch pedal feel heavy or grabbing point changed?
  • Any grinding noises when changing gear?
  • Clutch slipping - engine revs but car doesn't accelerate?

Automatic Transmission Questions

  • Harsh shifting or delayed gear changes?
  • Slipping - engine revs without acceleration?
  • Any unusual transmission fluid leaks or smells?
  • Does it stay in gear properly when stopped?

📱 Technology-Enhanced Diagnostics

Using modern technology to improve remote diagnostic accuracy

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Visual Diagnostic Tools

Guide customers to provide visual information remotely.

Photo/Video Requests

  • Dashboard warning lights (clear, close-up photos)
  • Engine bay overview (bonnet open, engine visible)
  • Visible leaks or damage (specific areas)
  • Exhaust smoke (video while running)
  • Noise recording (audio while engine running)
  • Fluid levels and colours (dipstick readings)

Visual Request Script

AI: "To help our mechanic prepare the right tools and parts, could you take a photo of your dashboard with the warning light showing?" Customer: "Yes, I can do that" AI: "Great.You can send it via WhatsApp to [number] or email to [address].A clear, close-up photo will help us identify the exact warning."
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OBD Code Integration

Guide tech-savvy customers to retrieve diagnostic codes.

OBD Reader Questions

  • Do you have an OBD code reader or diagnostic tool?
  • Can you access the diagnostic port under the dashboard?
  • Any smartphone apps connected to OBD adapters?
  • What specific error codes are showing?

Code Reader Script

AI: "I notice you mentioned having a code reader.If you're comfortable using it, the diagnostic codes would help our mechanic prepare." Customer: "I've got the app on my phone" AI: "Perfect.If you could read the codes and tell me what it shows, that'll help us bring the right equipment."
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Code Reader Benefits

OBD codes can eliminate 60% of diagnostic time and ensure the mechanic arrives with correct parts and tools.

🛠️ Diagnostic-Based Job Preparation

Using diagnostic information to prepare tools, parts, and approach

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Equipment Preparation

Match diagnostic findings to required tools and equipment.

Suspected Issue Essential Tools Likely Parts
Battery/Charging Multimeter, battery tester, jump leads Battery, alternator belt
Brake Issues Brake tools, pressure bleeder Brake pads, fluid, discs
Engine Performance OBD scanner, compression tester Spark plugs, filters, fluids
Suspension/Steering Wheel alignment tools, torque wrench Bushes, shock absorbers
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Pre-Arrival Summary

Comprehensive job briefing based on diagnostic questioning.

Mechanic Briefing Checklist

Vehicle details and customer location confirmed
Primary symptoms and fault description documented
Diagnostic codes retrieved (if available)
Recent service history and related work noted
Suspected diagnosis and probability assessment
Required tools and likely parts identified
Customer expectations and quote provided

Job Summary Template

CUSTOMER: [Name] - [Phone] - [Location] VEHICLE: [Year] [Make] [Model] - [Mileage] - [Fuel Type] PRIMARY SYMPTOM: [Customer description] ONSET: [When started] - [Sudden/Gradual] CONDITIONS: [When occurs] - [Frequency] DIAGNOSTIC CODES: [If available] RECENT WORK: [Last 6 months] SUSPECTED CAUSE: [Primary/Secondary theories] TOOLS REQUIRED: [Specific equipment] PARTS NEEDED: [Likely components] ESTIMATED TIME: [Hours] - QUOTE: [£Amount]
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Master Professional Diagnostics

Implement systematic diagnostic questioning in your mobile mechanic AI system. Improve first-fix rates and customer satisfaction with professional fault diagnosis.

🔍 Setup Diagnostic AI
📊 85%+ first-fix rate improvement 🎯 Professional diagnostic protocols 🛠️ Intelligent job preparation
💡

Custom Diagnostic Setup

Our team can configure diagnostic questioning specific to your specialties and common local vehicle issues. Contact us for specialised setup.