Engine MIL Inoperative or indicates a malfunction

[Tcollis]

Hi all, I have the above as an MOT fail, code (8.2.1.2(h)).

Does anyone know how big a job this might be to fix?

Thank you very much,

Tim

[andypryce]

Depends on the cause, is car driving ok? Should be able to get fault codes from code reader, if you can then post back with them and people should be able to advise. Regards

[BrianG]

Don't panic! As has already been said you need to get the code(s) read to find the cause of the MIL coming on. One thing you can easily check without a code reader is the engine dip stick. If this is not pushed back in fully you will get the MIL come on (as I know from experience). An air leak here causes a change in the crankcase purging system and alters the fuelling at low rpm; this change flags the fault. As well as being pushed fully home, check that it's not caused by a worn or missing o-ring at the dip stick handle.

[Tcollis]

Thanks all, the mechanic must have resolved that code as it's gone and the MOT has been passed. I do though have another intermittent one which is P1646 and I think this is putting the engine fault light on the dashboard. Is it just one of those things I'm going to have to live with or would people recommend that I try and get it fixed? Thanks

[BrianG]

P1646 fault code is for the upstream Heated Oxygen Sensor on Bank 1, part of the catalytic converter/emission control system. This will give a MIL fault after 2 drive cycles, hence the "intermittent" character. It will mean your car is not running efficiently as there will be incorrect air/fuel mixture on that bank. It is either the sensor at fault and/or the associated wiring so it is worth getting it fixed.

This fault could have resulted in an MOT fail as it will have pushed the emissions up considerably and these engines are very clean running. If you got an emissions test printout with the MOT pass slip; for a correctly running engine this should normally show carbon monoxide (CO), percentage test limit 0.2%, as something around a tenth of that at 0.02% or even lower. Unburnt hydrocarbons (HC) have a limit of 200 parts per million, last test on my car was 2 ppm.