Engine management light - no fault found

Bigwheels1111

Annie1960 said:

Bigwheels1111 said:

Annie1960 said:

Bigwheels1111 said:

Buy an OBD2 Code reader.
Just a basic £15 one will do.
Plug in read codes. Note down code.
Then erase.
Look up codes just in case they come back.
My car gives a code for faulty Nox sensor.
Clear code and off I go.

Where would I plug it in?

As DanDare999 said, make and model would help.

Some are easy to find some are not.

Vectra hide it under the ash tray and my Peugeot has it in the glove box behind a plastic cover. Took days to find it.

Others have it under the steering wheel above the pedals or under the glove box.

Vauxhall Astra, January 2020 model.

Look here

https://www.youtube.com/watch?v=VpswiD41_Fc

Annie1960

Would it invalidate the manufacturer's guarantee (or any extended warranty I might buy) if I used such a device myself?

Goudy

There are different types of diagnostic trouble codes that are linked to the engine management light.

Some are hard codes, a definite fault like a sensor with a broken circuit.

Others are difference related. The engine management starts seeing a difference that shouldn't be there and if it detects the same fault a few times in the same drive cycle it will flag a fault and light the EML on the dash.

These types of faults aren't always hard stored, quite often they will reset themselves if the same fault isn't detected again when the ignition is switched off and back on again.
They can sometimes be stored as "pending" or nothing at all.

Often these difference related ones are related to the fueling or emissions.

If the EML of off and is staying off, I wouldn't worry too much about it.

If it returns and stays on (even after a restart) then a decent code reader should be able to pull the code from the ECU.
And no, it won't invalidate your warranty though fixing the problem badly might. 

MX5huggy

Annie1960 said:

Would it invalidate the manufacturer's guarantee (or any extended warranty I might buy) if I used such a device myself?

While it’s covered by the original manufacturer warranty just keep taking back to the dealer doing anything else has the potential to give them a reason to try to charge you or wriggle out of paying for that new engine because you cleared a sensor error 6 weeks before. They probably should not be charging you for diagnostics under warranty. 

Ibrahim5

I bought a car with a main dealer warranty. I had a problem so I phoned the dealer up. They said there would be a diagnostics charge because the manufacturer wouldn't pay them unless they could prove that they had replaced a faulty component. I told them that I wasn't in the slightest bit interested in getting involved in silly squabbles between the manufacturers and dealers and I had a faulty vehicle and a warranty and I wanted it fixing and I wouldn't be paying 'diagnostic fees'. They just said "OK bring it in". A lot of these things they will charge people who don't argue and won't charge people who do.