Engine management light & MoT

[VolvoFan]

Originally Posted by RUTV70

Have you had the codes read.?

Neil

Yes, in November 2010 - yes, 2010! The report stated that the fuel system was lean; but the self-learn program was unable to complete. The prognosis was that "an air-flow meter (throttle body) was required." I wouldn't think the mixture strength is too far out as the plugs look okay and running seems to be quite normal.

Is it possible that the engine management system is over-sensitive?

Well, I've driven the car several thousand miles since then, with no noticeable ill effects in performance or economy.

I was advised to run the car as usual and wait until symptoms show before going to the expense of a new AFM.

The only reason I'm concerned about the engine warning light is the MoT! I suppose testers would be wise to the fact if I removed the warning lamp bulb?!

[VolvoFan]

Originally Posted by banksy66

Good question. 99% of the time I find it's a sensor fialure rather than an actual component failure, so you won't necessarily notice any difference in the way a car drives just because the engine light is on

Thanks, but the fault reader didn't specify a faulty sensor.

[RUTV70]

I'd still be getting the codes read...again.!....and getting any actual code numbers.!
At least if you've got those then you have a good chance of finding out what's amiss.
Taking the bulb out is addressing the symptom...not the cause....and the light will be conspicuous by it's absence surely.?

What model are we talkin' about here.?...

Neil

[banksy66]

Originally Posted by VolvoFan

Thanks, but the fault reader didn't specify a faulty sensor.

A fault code reader only reads a fault code, it won't actually tell you what's wrong or what is causing it

As an example, I had a code read yesterday on a Polo. Fault code related to 2issues with the 02 sensor before the catalytic converter, creating the impression that the sensor had fialed. The fault was actually a broken wire to the sensor, but at least the reader sent us in the right direction

[tt82]

Have the garage clear the light before they do the MOT. It might stay off long enough for it pass.

[VolvoFan]

Originally Posted by tt82

Have the garage clear the light before they do the MOT. It might stay off long enough for it pass.

Thanks. I already considered doing this!

[VolvoFan]

I did get the code numbers, which is why the technician pointed towards replacing the AFM/throttle body.

Incidentally, the model I'm referring to is a Nissan Micra 1.4 SE (2001) K11 (old shape).
I wouldn't know whether fault code numbers are the same on Volvos - or any other vehicles, for that matter. Just for the record the code is PO171.

An ex-work colleague once told me of when she had an engine management warning light come on a Saab, and drove around for ages with no ill effects. She even made a couple of return trips to Germany and the light was still on.

[DaveNP]

We had a problem with our Nissan Almera when the engine light would come on at random then go off again with no appreciable effect on performance. Checking the codes gave an indication that it was running lean, looking at the exhaust pipe showed loads of soot eg running rich. The actual problem was the lamda sensor before the cat was knackered and giving a false lean reading but not a code for a sensor fault. SEnsor replaced solved the problem.

The fact that you can still drive the car (locally or to Germany) doesn't prove it's running well, and the codes don't always tell the whole story.

[VolvoFan]

I disconnected the battery last night, and when I re-connected it this morning, the engine management light went out as soon as the engine started. How can this be accounted for? If it lights up again I will let you know.

[Marty Dolomite]

Disconnecting the battery is a trick of the roadside guys just to get that car out of their area so they dont have to tow it, the ECU will temporarly (sp?) forget the fault for a while.
It will come back on at some point depending on what is causing it.