Welcome to Terrett Automotive's CAS Auto Services

When Should You Book a Diagnostic Check? 

Look out for these common signs that your car needs a diagnostic: 

• Engine management or emissions light illuminated 
• Rough idle, hesitation, or misfires 
• Hard starting or stalling 
• Poor fuel economy or reduced performance 
• Unusual smoke, smells, or noises 
• Automatic gearbox shifting oddly 
• Battery, ABS, or airbag lights appearing 
• Cooling fans running constantly or overheating 

If any of these sound familiar, avoid DIY guesswork. A proper diagnosis saves time and prevents bigger repairs later. 

What We Check During a Diagnostic Appointment 

Our approach combines electronic scanning with practical mechanical checks: 

• OBD fault code scan to identify stored, pending, and historic codes 
• Live data analysis for sensors such as oxygen, MAF, MAP, coolant temperature, and fuel trims 
• Visual and electrical checks of wiring, connectors, grounds, and fuses 
• Battery and charging system test to rule out low-voltage faults 
• Fuel, air, and ignition checks where symptoms suggest a mechanical issue 
• Road test to reproduce the fault under real conditions 
• Clear explanations of findings and recommended next steps 

We will never fit parts on guesswork. You approve any work before we proceed. 

Why Choose Us for Diagnostic Checks in Bristol? 

• Family-run and local: Friendly, honest advice from a team that cares about the community 
• Combined 50 years of experience: Real-world know-how alongside modern tools 
• All makes and models: From city cars to SUVs and light vans 
• Rapid turnaround: Same-day assessments wherever possible 
• Clear communication: Plain-English explanations and updates throughout 
• Free maintenance tips: Practical advice to keep your vehicle running better for longer 

Examples of Faults We Commonly Diagnose 

Here are typical issues we see and fix: 

• Misfire and rough running: Coil packs, plugs, injectors, or vacuum leaks 
• Poor fuel economy: Oxygen sensor performance or MAF contamination 
• Emissions or catalyst warnings: Sensor data out of range or exhaust leaks 
• Starting and charging faults: Weak batteries, alternators, or parasitic draws 
• EGR and intake problems: Carbon build-up causing hesitation or smoke 
• Temperature control issues: Thermostat not regulating correctly or cooling fan faults 

We will explain what the data shows and the most sensible, cost-effective fix. 

What to Expect on the Day 

• Check in and describe symptoms: Tell us when the fault appears, fuel level, weather, or speeds 
• Initial scan and safety check: We capture codes and verify basics 
• Live data and test drive: Recreate conditions to see what the car is doing 
• Report and recommendations: You receive a clear summary with next steps 
• Your approval before work: No surprises, no unnecessary parts 

Book Your Diagnostic Check in Bristol Today 

Do not let a warning light turn into a bigger repair. Book your diagnostic check with Terrett Automotive's CAS Auto Services in Bristol today. We will find the fault, explain it clearly, and get you back on the road quickly and safely.