Engine Diagnostics

What you might be noticing

• —Check-engine light on, flashing, or coming and going
• —Rough idle, hesitation, or a stumble under acceleration
• —Fuel economy that has quietly gotten worse
• —Hard starting, or cranking longer than it used to
• —A misfire you can feel through the seat
• —Failed emissions test

How we do the job

1. 01

   Pull every code, not just the first

   We read stored and pending codes across all modules, plus freeze-frame data - the snapshot of what the engine was doing at the moment the fault set. That context is usually more useful than the code itself.

2. 02

   Look at live data

   Fuel trims, sensor voltages, misfire counters per cylinder. This is where a lean code stops being a guess: fuel trims that are bad at idle and fine at speed point at a vacuum leak, not a failing sensor.

3. 03

   Test the part before replacing it

   A sensor that reads implausibly might be faulty, or it might be reporting a real condition accurately. There is a test for the difference. We do the test.

4. 04

   Tell you what we found and what it costs

   You get the actual fault in plain language, what it will take to fix, and whether it needs doing now or can wait. If the answer is a loose fuel cap, we will tell you it was a loose fuel cap.

5. 05

   Verify the repair

   Codes cleared, drive cycle completed, monitors confirmed ready. A repair is not finished when the light goes off - it is finished when the computer has re-run its own tests and passed.

What it costs

Diagnosis is charged for the time it takes, and you will know that figure before we start. It is a real service with a real cost, because it is the part that saves you from buying parts you did not need. Simple faults resolve quickly; intermittent electrical problems take longer, and we will keep you posted rather than quietly running up hours.

Common questions

The parts store read my code for free. Why pay for diagnosis?

Because those are two different things. A free code read tells you the number. Diagnosis tells you the cause - and the cause is frequently not the part the code appears to name. Paying once for the right answer is cheaper than buying two wrong parts.

My check-engine light is flashing. Is that different?

Yes, and it matters. A steady light means a fault is stored. A flashing light generally means an active misfire severe enough to damage the catalytic converter. Reduce speed, avoid heavy throttle, and get it looked at promptly rather than finishing the week.

Can I keep driving with the light on?

Often, but you are driving without knowing what is wrong. Some faults are harmless; some quietly destroy something expensive. The point of diagnosis is to find out which one you have.

Will altitude affect my engine?

The engine management compensates for thinner air automatically, so a healthy car simply makes a bit less power up here. But a marginal component - a weak fuel pump, a tired ignition coil - can show symptoms at altitude that it would hide at sea level.