Check Engine Light Diagnosis
Also called engine light on
A check engine light means the engine management system has detected something outside its expected range. This service reads the codes, examines live data, and tests the circuit or condition behind the fault. A flashing light means a misfire that can damage the catalytic converter, so it needs immediate attention. At the end you know what is wrong and what it costs to fix. The diagnosis is not the repair, and the light will return until the cause is corrected.
What the job includes
- Codes and freeze frame data recorded before any clearing
- Live data reviewed, including fuel trims, sensor values and load
- Road test to reproduce the conditions in which the fault occurred
- Circuit testing of the suspect component, its supply and its earth
- Vacuum and exhaust leaks checked, as these cause many engine light faults
- Written findings with a repair quote
Signs you need this
- The check engine light is on steadily
- The light flashes, which usually means an active misfire
- The light comes on and goes off again on different journeys
- Loss of power, rough running or higher fuel consumption alongside the light
- The light returned after being cleared somewhere else
Not all of these have to be present, and one of them on its own can mean something else entirely. That is what the diagnosis is for.
How we do it
Record the evidence
Codes and freeze frame data are captured first, because they show the exact conditions when the fault occurred.
Read the live data
Fuel trims and sensor values are examined, which often reveal the cause more clearly than the code itself.
Reproduce on the road
The car is driven in the conditions recorded in the freeze frame so the fault can be observed as it happens.
Test the circuit
The suspect component, its wiring, supply and earth are tested so the faulty item is proven rather than assumed.
Report and quote
You receive the finding, the evidence behind it, and the cost of the repair before any work is carried out.
How we work
The same on every job, which is why we can write it down.
Diagnosis before quote
We find the fault first. A price given over the phone for a noise nobody has heard is a guess.
The price is agreed first
You approve the work and the cost before a spanner is picked up. Extra work means another call.
Parts you can check
We tell you whether a part is genuine, OEM, aftermarket or used, and what each one costs.
Old parts returned
Ask and we will hand back whatever we replaced. It is the simplest proof that the job was done.
Book check engine light diagnosis
Fill this in and a person will call you back to confirm the time and the price. Only your name and one way to reach you are required.
Before you book
Questions we get asked
If your question is not here, ask it. We would rather answer honestly now than have you find out after booking.