Car diagnostics

A warning light, a noise you can’t place, a smell that wasn’t there last week, or a car that just doesn’t feel right. You don’t need to know what any of it means before you ring. Diagnostics is the work of finding out which part has failed, and it happens before anyone quotes you for a repair.

Signs your car needs a diagnostic check

• The check engine light is on, flashing, or comes on and goes off again.
• The car is drinking more fuel than it used to, or idling roughly.
• It hesitates, surges, or drops into limp mode under load.
• A noise or vibration that changes with engine speed or with road speed.
• A smell of fuel, coolant, oil or burning that wasn’t there before.
• A fault that only shows up when the engine is cold, or only once it’s hot.

What a diagnostic check involves

It starts with what the driver noticed, because that narrows the field faster than anything else does. Then the car’s own systems are read for stored fault codes, and the live data coming off the sensors is watched while the engine runs. A code points at a circuit or a system, and the part that failed still has to be found by testing.

From there it’s measurement. Voltages, pressures, temperatures and the figures the car itself reports, all compared against what the manufacturer says they should be. Some faults show themselves in a few minutes. Intermittent ones take longer, because the fault has to be happening at the moment it’s measured.

Not every fault sets a code. Worn components, leaks and ordinary mechanical wear often show up as a symptom with nothing stored at all, which is why a road test and a look over the car are still part of the job. Qualified motor mechanics do the work, with current engine diagnostic equipment at the workshop.

Diagnostics with a service or a pink slip

If a fault turns up during a logbook service or an eSafety check, it gets reported to you with everything else found that day and quoted on its own. If you’re booking a diagnostic check and your rego happens to be due, say so and we can line the pink slip up with it. Anything that follows on from the diagnosis is handled as ordinary mechanical repair work, quoted the same way.

What to tell us when you book

Tell us what the car is doing, when it started, and what you were doing at the time. Cold or hot, idling or under load, in the wet or the dry. If a light is on, say which one and whether it stays on or comes and goes. If it’s a noise, tell us where you hear it from and whether it changes with speed.

Questions about car diagnostics

What does the check engine light mean?

That the engine management system has recorded a fault. It covers a lot of ground, from a loose fuel cap to a failing sensor. A light that flashes is the urgent one, and a car doing that shouldn’t be driven far.

Can you read the code and tell me over the phone?

A code narrows things down, it doesn’t finish the job. Two cars carrying the same stored code can need two different repairs, so the code gets confirmed by testing before any part is replaced.

The light went off by itself. Do I still need it looked at?

Usually yes. A fault that clears itself normally leaves the code stored in the car’s memory, and an intermittent fault tends to come back. Reading the history while it’s quiet is easier than chasing it later.

Will I get a price before any work happens?

Yes. We tell you what we found, quote it, and wait for you to say yes. Nothing gets done until you’ve agreed to that quote, and the bill afterwards is itemised so you can see every job and every part on it.