A warning light is your car trying to tell you something specific — and a £15 code-read at a parts counter is like answering the phone and hanging up. Proper diagnostics means every module scanned, live data analysed while the engine runs, and the findings explained in plain English with a written report. £40, no upsell theatre, and you decide what happens next.
"P0299 — underboost" names the symptom. Finding out *why* is the actual job.
Here's what the £15 code-read can't tell you: that P0299 underboost code might be a split intercooler hose, a lazy wastegate actuator, a tired MAP sensor or a boost leak the size of a pinhole. Same code, four different fixes, four very different bills. Reading the code is the first thirty seconds of diagnostics; everything that makes the answer right happens after.
Our session interrogates every control module on the car — engine, transmission, ABS, airbags, body, comfort, the lot — because faults travel across systems and the module that logged the code isn't always the module with the problem. Then comes live data: watching sensors in real time while the engine runs and, where the symptom demands it, while the car is driven. Frozen-frame data from the moment the fault tripped, actuator tests to confirm components respond, and a judgement built on evidence.
What you get is the finding in plain English — what's wrong, how certain we are, what fixing it involves and roughly what it should cost — in writing, with the codes and data attached. We don't do repairs-by-ambush: many faults have fixes we can do on the spot (and we'll quote them), some belong at a specialist, and either way the report is yours to act on wherever you choose. It's also the exact health check every FLR remap starts with — diagnostics isn't a sideline here, it's the foundation.
Six layers of investigation — tap each one to see what it catches.
Every control unit interrogated — not just the engine. Faults hide in modules the cheap tools never visit.
A modern car runs thirty-plus computers, and a "mystery" engine symptom is regularly a body module, a gateway gremlin or a comfort system dragging a shared network down. Scanning everything first means the real culprit can't hide behind the obvious suspect.
Codes read with judgement — which are the cause, which are the echo, which are ancient history.
A car can carry fifteen stored codes of which one matters. Age, frequency, freeze-frame conditions and cross-module patterns separate the live fault from the noise — interpretation is the skill the £15 read doesn't include.
Sensors watched in real time — running, revving and where needed, driven — to catch faults codes never log.
Plenty of real problems never trip a code: a MAF reading 10% low, a boost curve that sags warm, a misfire counter climbing quietly. Live parameters against known-good values find the faults that live between the thresholds.
Components commanded directly — pumps, valves, flaps — to prove whether they respond or just pretend to.
Sensors tell you what the ECU sees; actuator tests prove what the hardware does. Commanding an EGR valve, a swirl flap or a fuel pump directly turns "probably the valve" into "the valve — watched it fail".
The same session validates a car for tuning — because calibrating over a fault helps nobody.
Thinking about a remap? This is the gateway: boost integrity, fuelling health, no suppressed faults waiting to bloom under higher load. Pass, and the tune proceeds with confidence; fail, and you've saved a remap budget from being spent disguising a problem.
Findings, confidence level, recommended next step and rough cost — documented and yours.
The report travels with you: use it for our quote, a specialist's bench, a warranty conversation or a used-car negotiation. Paying £40 for the truth before a £400 repair is the best ratio in motoring.
This is the shape of a full-system session — modules swept, faults surfaced, evidence logged.
| Step | £15 code read | FLR session |
|---|---|---|
| Engine codes | Read only | Read & interpreted |
| All other modules | — | Scanned |
| Live data & freeze-frame | — | Analysed |
| Actuator tests | — | Where relevant |
| Written report | — | Included |
From symptoms conversation to written report — how a diagnostic actually runs.
Three truths most garages would rather not put in writing.
Intermittent electrical gremlins that vanish for weeks can need data logged over time. Anyone promising every fault solved in an hour is selling confidence, not engineering.
If your fault needs longer-term logging or a specialist rig, the report says so and maps the route. You'll always leave knowing more than you arrived with — and what the honest next step costs.
Wiping the light without fixing the cause just resets the countdown — and destroys the freeze-frame evidence the next diagnosis needed.
We clear codes after the cause is found or as a deliberate, explained test step — never as a "there you go, light's off" service. That favour is how £40 problems become £400 ones.
Diagnostic fees that magically become "free with repair" are a sales funnel wearing a lab coat. The incentive should be the right answer, not the biggest job.
£40 buys the finding, full stop. If we can fix it, you get a quote you're free to decline; if someone else should, the report makes their job faster. No ambush, no theatre.
Not sure which applies? Describe the symptoms — we'll point you at the right session before you spend anything.
The free scan reads engine codes and hands you a printout — that's the first thirty seconds of our session. We scan every module on the car, analyse live sensor data with the engine running, pull freeze-frame evidence, run actuator tests where relevant, and interpret it all into a finding with a confidence level. The difference is the difference between a thermometer and a doctor.
Usually, yes. Most faults store historic codes and freeze-frame data — a snapshot of conditions at the moment the fault tripped — even after the light extinguishes. That history plus live-data comparison often identifies an intermittent fault between episodes. The worst case is honest: we tell you what to watch for and how to catch it in the act next time.
No — the £40 buys the answer, and the answer is the product. If it's something we fix (software faults, sensors, many common repairs), you'll get a take-it-or-leave-it quote. If it belongs at a gearbox specialist or bodyshop, the report says so and saves them an hour of rediscovery. Plenty of customers take the report elsewhere; that's exactly how it's designed.
Our equipment covers the vast majority of makes — European, Japanese, Korean and most others — at a depth close to dealer level on common platforms. A handful of exotics and very new models have locked-down systems with limited third-party access. Send the reg before booking and we'll confirm coverage honestly rather than finding out together.
It's some of the best £40 in motoring. A pre-purchase scan reveals cleared-but-stored faults, crash-event records in airbag modules, mileage inconsistencies across control units, and suppressed warning lights — the electronic history the seller's ad didn't mention. Ten minutes of data has talked more than one of our customers out of a very expensive mistake.
Yes — the full session travels: same scan depth, same live-data analysis, same written report, anywhere across our coverage area, seven days a week with no call-out fee. The only cases that prefer the workshop are faults needing extended drive-cycle testing or equipment that doesn't fit in the van. We'll tell you which yours is when you describe the symptoms.
When the symptom needs tracing to its root and clearing properly — the investigation service.
From £40 See fault finding // Clean bill of health? Stage 1 ECU RemapA healthy scan is the green light — the diagnostic session is the first step of every remap anyway.
£150 See Stage 1 // While we're plugged in Vehicle CodingHidden features your car already supports, enabled properly — often in the same visit.
From £25 See coding£40 for the full story — every module, live data, plain English, in writing. Workshop or your driveway, seven days a week.