A warning light or a running fault can have many causes. We run a full fault-code scan, analyse live data, and test compression where needed to pinpoint the actual problem.
You get written findings and a fixed quote to fix it — no guesswork, no parts-cannon.
Why a code reader isn't a diagnosis
A fault code tells you which circuit reported a problem, not what's wrong. P0171 doesn't mean 'replace the oxygen sensor' — it means the engine is running lean, which could be a vacuum leak, a failing mass airflow sensor, low fuel pressure, or an exhaust leak fooling the sensor. Reading codes takes two minutes and anyone can do it. Interpreting them correctly is the actual work, and it's the difference between fixing the fault and replacing parts until the light goes out.
What we actually do
We start with a full system scan, including manufacturer-specific codes that generic readers miss, and check freeze-frame data to see the conditions when the fault triggered. Then we work with live data — fuel trims, sensor voltages, boost and rail pressures, misfire counters — with the engine running and, where necessary, on the road. Mechanical testing follows if the data points that way: compression, leak-down, smoke testing for vacuum leaks.
Intermittent faults
The hardest faults are the ones that aren't present when the car is on the ramp. Data logging over a drive cycle captures what a static test never will, letting us see the moment the fault appears and what the surrounding sensors were doing. If a fault only shows up cold, or after twenty minutes at motorway speed, that's what we replicate.
What you get
You get a written explanation of what we found, what we tested to prove it, and a fixed quote to fix it. If we can't prove the cause, we tell you that too rather than guessing on your money. The diagnostic charge is credited against the repair if you go ahead with us.
How we do it, step by step
- 01
Full system scan
All modules read, including manufacturer-specific codes, with freeze-frame data captured.
- 02
Live data analysis
Fuel trims, sensor outputs and pressures analysed with the engine running.
- 03
Road test / logging
Data logged on the road where the fault is intermittent or load-dependent.
- 04
Mechanical testing
Compression, leak-down or smoke testing where the data indicates a mechanical cause.
- 05
Written findings and quote
You get the evidence, the cause, and a fixed price to put it right.
What affects the price
- ›How many systems are involved and whether the fault is intermittent
- ›Whether road-test data logging is needed to reproduce it
- ›Additional mechanical testing (compression, leak-down, smoke)
Typical turnaround: Usually same day
Warranty: Diagnostic time is credited against the repair if you go ahead with us.
Rebuild, reconditioned or replacement — which is right?
The cheapest route depends on your engine. Here's how the three options compare — we'll advise honestly once we've seen it.
| Option | Typical price | Time | Best when |
|---|---|---|---|
| Engine rebuild | From £1,200 | 2–4 days | The block is sound and you want to keep your original engine |
| Reconditioned engine | From £900 | 2–5 days | Your engine is beyond economical repair |
| Engine replacement | On quote | 1–3 days | You need the fastest route back on the road |
Prices are indicative starting points. We confirm one fixed price before any work begins.
Frequently asked questions
My engine light is on — is it serious?
It might be minor or serious — the only way to know is to read the fault properly. We diagnose the real cause and tell you straight.
How much is a diagnostic?
Diagnostics start from £90, and we put that toward the repair if you go ahead with us.
Can you diagnose intermittent faults?
Yes — live data logging helps us catch faults that only appear when driving.
Will you just read the codes?
No. Reading codes is the starting point, not the diagnosis. We interpret them alongside live data and mechanical testing to find the actual cause.
Is the diagnostic fee refundable?
It's credited against the repair if you go ahead with us.
My light comes on then goes off again — can you still find it?
Usually yes. Stored and pending codes plus freeze-frame data often survive even when the light clears, and we can log data on the road to catch it happening.
How long does a diagnostic take?
Most are completed the same day. Intermittent faults needing road-test logging can take longer, and we'll tell you up front if that's likely.
Can you diagnose faults on any make?
We cover all the major makes and use manufacturer-specific data as well as generic protocols.