What is a Vehicle Diagnostic Test? A Comprehensive Guide by M&BM Motors, Grays

July 1, 2025

Addressing issues early often reduces repair costs

A person is carrying out an engine diagnostic hood of a car.

At M&BM Motors here in Grays, Essex, we understand that your vehicle is more than just a mode of transport – it’s part of your daily life.


Whether it’s commuting to work, the school run, or those long weekend drives, keeping your vehicle running smoothly is essential.


One of the most effective ways to ensure your car stays in top condition is through regular vehicle diagnostic tests.


But what exactly is a vehicle diagnostic test, and why is it important? Let’s break it down.


What is a Vehicle Diagnostic Test?

In simple terms, a vehicle diagnostic test is like a health check-up for your car.


Modern vehicles come equipped with sophisticated onboard computer systems that monitor and control various components, from the engine to the braking system and even exhaust emissions.


A diagnostic test involves connecting your vehicle to a specialised scanner that communicates with the car’s onboard computer.


This scanner reads fault codes (known as Diagnostic Trouble Codes or DTCs) and pinpoints any issues that may be affecting performance or safety.


What Does a Diagnostic Test Check?

Here at M&BM Motors, when we carry out a diagnostic check, we look at several key areas, including:


  • Engine performance issues
  • Transmission faults
  • Exhaust system problems
  • Brake system warnings
  • Airbag and safety restraint systems
  • Emission levels
  • Battery and charging system health


If you’ve noticed a warning light on your dashboard – whether it’s the engine management light, ABS light, or any other indicator – a diagnostic test is the fastest and most reliable way to identify the root cause.

A close up of the engine of a car with the bonet open.

Why Are Vehicle Diagnostics Important?


Many car problems start small but, if left unchecked, can develop into major repairs. By catching issues early with a diagnostic test, you can avoid costly breakdowns and keep your vehicle safe and roadworthy.


Some key benefits include:


  • Early Detection of Problems: Early detection can prevent minor faults from turning into major costly repairs.
  • Save Money: Addressing issues early often reduces repair costs.
  • Improve Safety: Faulty brakes or steering components are dangerous. Diagnostics help spot these problems early.
  • Better Fuel Efficiency: Problems like faulty sensors can cause poor fuel consumption.


How Long Does a Diagnostic Test Take?


In most cases, a diagnostic check at M&BM Motors takes around 30 minutes to an hour. If the test reveals any faults, our experienced technicians will explain the findings in plain English – no confusing jargon – and discuss the best way to fix the problem.


Do I Need a Diagnostic Test If My Car Feels Fine?


Even if your vehicle seems to be running smoothly, modern cars can store hidden fault codes that don’t trigger a warning light immediately. Regular diagnostic checks are especially recommended if:


  • Your car is due for a service
  • You’re preparing for a long journey
  • You’ve recently bought a used vehicle
  • You want peace of mind


Why Choose M&BM Motors for Diagnostics in Grays?


At M&BM Motors, we’ve built a reputation across Grays and the wider Essex area for honest, transparent service and high-quality workmanship.

Our technicians use the latest diagnostic tools compatible with all major makes and models, ensuring accurate results every time.


We pride ourselves on offering clear advice and no-obligation quotes. If your vehicle does need repair work following a diagnostic test, you’re in safe hands with our experienced team.


Book Your Vehicle Diagnostic Test Today


If you’re experiencing issues with your vehicle or simply want to ensure everything is running as it should, contact M&BM Motors today. You can book a diagnostic check by calling us on 01375 399955.

Google review for M&BM Motors
Vic Knight instructor at Gas Training & Assessment - gas courses in Basildon, Essex
Mark Page | M&BM Motors, Grays, Essex

If you have a question about this or any of our blogs, or our services then please do not hesitate to get in touch. 

We will always try and answer your question quickly and professionally. 
Get In Touch

Keep Your Car Roadworthy with M&BM Motors’ MOT Test Centre
By M&BM Motors January 13, 2025
An MOT test is more than just ticking a legal box; it’s a vital check-up to ensure your vehicle is safe, efficient, and roadworthy. M&BM Motors MOT Test.
How to Safely Defrost Your Car This Winter: Tips from M&B Motors
By M&BM Motors December 9, 2024
Clear your windscreen and windows fully before driving. Obstructed views are dangerous and illegal. Take time to defrost properly for safe travels.
Top Low-Tax Cars in the UK (Excluding Fully Electric Vehicles)
By M&BM Motors November 5, 2024
There are several hybrid and highly efficient petrol and diesel options that offer impressive fuel economy and low emissions, keeping tax costs down.
Top 5 Signs Your Car Needs Immediate Attention
By M&BM Motors October 24, 2024
The best way to avoid costly repairs is through preventative maintenance. Simple actions like regular oil changes, tyre rotations, and diagnostic checks can extend the life of your vehicle and save you from unexpected expenses.
Protect Your Car from Rodent Damage with M&BM Motors
By M&BM Motors June 13, 2024
Protect your car from costly rodent damage with our specialised deterrent treatment. Contact M&BM Motors today to schedule your appointment and ensure your vehicle stays rodent-free.
Enhance Safety and Performance: The Importance of Brake Fluid Changes
By M&BM Motors May 8, 2024
As a trusted garage in Grays, we're here to shed light on why regular brake fluid changes are vital for every vehicle owner. Read more...
Top tips on how to choose a reputable garage?
October 18, 2023
To avoid falling victim to a shoddy garage, there are a few key factors to consider. Read our top tips. Read more...
What to do if I breakdown on a motorway - step by step guide
By M&BM Motors July 17, 2023
What to do if I breakdown on a motorway. Here's our quick step by step guide on what to do if you breakdown on the motorway. Read more to find out...
Do electric and hybrid cars need servicing?
By M&BM Motors April 4, 2023
Looking after an electric vehicle and hybrid car is similar to maintaining a traditional petrol car - there are a few straightforward measures you must take to keep it secured and dependable. Let us quickly go over the fundamentals. Read more>>
Used car checklist top tips on buying a second hand car
By Mark Page December 1, 2021
Here's our top tips on buying a second hand car. It's important to not buy a dodgy car. M&BM Motors of Grays, Essex have put together a second hand car checklist - don't get caught out when buying a used car. M&BM Motors Mechanics Garage can assist.
Show More