A free code read
“P0299 — turbo underboost. That will be your turbo.”
- Reads stored codes from the engine module only
- Points at a circuit, not a component
- No testing, no live data, no evidence
- Leads to parts being replaced on a guess
Diagnostics
Find the fault. Then fix it once.
A code tells you which circuit complained. It does not tell you whether the sensor, the wiring, the connector, the module or the mechanical part underneath is at fault. We test the circuit to find out, which is what stops you buying parts that change nothing.
Book a diagnostic session
- From
- £24.99
- Session length
- 60-90 minutes
The difference
Code reading is not diagnosis
Both take a few minutes at the OBD port. Only one of them tells you what to do next.
A diagnostic session here
“Boost is being requested and not delivered. Actuator responds. There is a split in the intercooler hose.”
- Every module scanned, with freeze frame and stored history
- Circuit tested with a scope and a current clamp
- Fault reproduced under load where possible
- Written report, evidence, and a costed repair plan
The session
Sixty to ninety minutes, four stages
Complex or genuinely intermittent faults sometimes need a second session with a logger fitted. If so, we will tell you at the end of the first, with a price, before you commit.
Full system scan
Every module on the vehicle, not just the engine. Gearbox, ABS, airbag, body, comfort and infotainment, with freeze frame data and stored history captured.
Live data analysis
Sensor values compared against what the vehicle should be seeing at that temperature, load and engine speed. This is where a plausible-looking reading gets caught out.
Circuit testing
Oscilloscope, multimeter and current clamp on the actual circuit. Signal quality, voltage drop and earth integrity, tested rather than assumed.
Report and plan
A written report listing codes, tests, evidence and conclusion, with a costed repair plan. Yours to keep, and to take elsewhere if you would rather.
What we see most
Six faults that walk through the door every week
If your car is doing one of these, we have almost certainly diagnosed the same thing on the same platform before.
Engine management light
Lit constantly, or on one day and gone the next. Either way the module has stored the evidence, and that is where we start.
Limp mode under load
Almost always boost, fuelling or a sensor dropping out when the engine is working hardest. Rarely reproducible on a driveway.
Intermittent electrical faults
Windows, locking, lights or dash warnings behaving differently in the wet, in the cold or over a speed bump. Usually a connector or a chafed loom.
Battery drain overnight
A module not going to sleep. We measure the parasitic draw and isolate the circuit rather than guessing at the battery.
ABS, traction or airbag lights
Safety systems that will fail an MOT. Frequently a wheel speed sensor, a ring, a clock spring or a corroded connector.
Rough running or misfire
Cylinder contribution, injector balance and compression testing tell us whether it is fuel, spark, air or mechanical before anything is replaced.
What it costs
Fair for the time it takes
Diagnosis is skilled labour with expensive equipment behind it. We charge for the time, and we credit it back in full if you have us carry out the repair.
- Standard diagnostic sessionFull scan, live data, circuit testing and written report. 60 to 90 minutes.
- £24.99
- Extended investigationFor genuinely intermittent faults needing a logger fitted and a second visit.
- From £120
- Pre-purchase health checkFull module scan and condition report before you buy a used vehicle.
- £55
- Module coding and retrofitCoding a replacement or retrofitted module to the vehicle. Quoted per job.
- From £45
The diagnostic fee is credited in full against any repair carried out from the same visit. If we cannot find your fault, we will tell you that too, and we will tell you what it would take to find it rather than charging you to keep looking.
Questions
Diagnostic questions
Mostly about intermittent faults, and about why this is different from the free code read at a parts counter.
My warning light comes on and then goes off. Can you still find it?
Yes, that is a large part of what we do. Intermittent faults leave freeze frame data and stored history in the module even after the light clears. We combine that with oscilloscope testing and, where necessary, a logging session so the fault is captured the next time it appears.
How is this different from a free code read at a parts shop?
A code reader tells you which circuit reported a problem. It does not tell you whether the sensor, the wiring, the connector, the module or the mechanical component is at fault. We test the circuit to establish which of those it actually is, which is what stops you buying parts that do not fix the car.
Do I get anything in writing?
Every diagnostic session ends with a written report listing the codes found, the tests performed, the evidence, our conclusion and a costed repair plan. It is yours to keep and to take elsewhere if you prefer.
Is the diagnostic fee refunded if you do the repair?
The fee is credited in full against any repair we carry out from the same visit.
Related work
Where diagnostics usually leads
DPF & Emissions Servicing
A great many DPF warnings turn out to be a sensor or an EGR fault. Diagnosis comes first.
Read moreHID, LED & Lighting Upgrades
Bulb-out warnings and canbus errors are diagnostic work as much as lighting work.
Read moreCustom Performance Remapping
We will not tune an engine with an unresolved fault. A clean scan is the prerequisite.
Read more
Stop guessing
Bring us the fault two other garages could not find
Tell us what the car does, when it does it and what has already been replaced. That history is genuinely useful, and it stops us repeating work you have already paid for.