Why Garages Quote for Diagnostics
FixMyCar explains why mechanics sometimes provide a diagnostic quote rather than a repair price.
Ellie Dyer-Brown
Monday July 21 2025
3 min read
If a quote seems unusually low, it’s likely for a diagnostic test rather than the full repair. This can be confusing if you’re expecting a repair cost upfront, but there are good reasons for this approach.
In this guide, we'll explain why mechanics often quote for diagnostics first and how this step fits into the overall repair process.
What is a car diagnostic?
A diagnostic test uses specialised tools and equipment to identify any problems with a car and its various systems. In addition to identifying underlying or developing issues, a diagnostic can also be tailored to pinpoint the cause of specific symptoms a driver has noticed.
Learn more about what’s involved in this guide.
Why garages sometimes quote for diagnostics
Mechanics sometimes provide a quote for a diagnostic test despite a driver requesting prices for a specific repair. There may be several reasons for this.
1. It prevents inaccurate quoting
It’s hard to provide an accurate price estimate for some more complex repair jobs without inspecting the vehicle first. Every car is built slightly differently – certain parts may be more difficult to access in some models compared to others, and additional issues may complicate the repair process.
Nobody likes to receive an invoice that’s £100 more expensive than the initial quote – that's why a diagnostic test is such a helpful tool. It eliminates the guesswork of quoting, ensuring there are no nasty surprises when you pay the final bill.
2. It ensures the right repair gets done
Different problems can have similar symptoms, making them difficult to diagnose, especially if you're not a trained mechanic. A diagnostic test allows the mechanic to confirm the root cause of the issue, rather than relying solely on a guess or description. This helps avoid unnecessary repairs, saves you money in the long run and ensures the correct repair is done the first time.
3. It helps spot hidden issues
Sometimes the problem you notice is just the tip of the iceberg. A warning light or strange noise may be caused by more than one issue or a deeper problem within the system. A diagnostic test can reveal faults you may not be aware of yet, helping you catch and address them early before they become bigger, more expensive problems.
4. It protects you and the garage
Without a proper diagnosis, a garage could carry out a repair you asked for, even if it doesn’t solve the issue. That’s frustrating for you and risky for the mechanic. By carrying out a diagnostic test first, the garage ensures they’re working from evidence, not assumptions. This builds trust, reduces the chance of disputes and ensures everyone’s on the same page.
While a diagnostic test may seem like an extra step, it’s a valuable part of the repair process. It gives the mechanic a clear picture of what’s going on, helps prevent wasted money on incorrect repairs and makes sure you get a fair and accurate quote.
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Ellie is FixMyCar's Content Manager. She has over three years of experience writing about cars and regularly collaborates with automotive experts to provide trustworthy advice for drivers that is easy understand. Her work has been featured in Yahoo! Finance, iNews, The Daily Express and The Sun. She has a BA in English literature and an MA in creative writing from Durham University. Outside of work, Ellie follows F1 and eagerly awaits Ferrari's next era of dominance in the sport. She drives a Suzuki Swift.