MaxiScan showing generic fault codes

[baldsparky]

Having purchased a MaxiScan MS309 I thought I would plug in and see what it throws up.

First of all I have no faults or check lights coming on the cars display.
The engine is running smooth and strong.
So I was just seeing what the unit is like in use.
Anyway to my surprise it detected 2 fault codes ie
Generic fuel trim bank 1 and fuel trim bank 2.

I had the option to clear these from the memory and thats what I have done.
I appreciate that you shouldnt just get rid of what can be valuable info but seeing as I have an engine that runs good, and nothing showing on the dash display I decided it was no big deal.

Can anyone tell me why and what this would mean.

Just curious as I dont think theres any realtime problem.

Many Thanks.

 

[shirleydrive]

Hi,
You shoud have 4 fuel trim readings. 2 on bank 1 and 2 from bank 2. There should be a short term fuel trim (STFT) on each bank and a long term fuel trim (LTFT) reading for each bank
STFT's should ideally be +1% and LTFT's should be no more than +/- 10%.
More than 1% indicates the the engine is running "lean", that is too much air in mixture. Readings less than 1% would indicate a "rich" mixture ie too much petrol.
The readings come from the lambda O2 sensors.
LTFT's are an accumulation of the STFT's.
Can you display real time data on your scanner? If so you should be able to monitor these readings.
The annual MOT checks Lambda readings ( should be 1 ), so if you have passed your latest test your fault codes are probably historical and not a problem.
Hope this helps,
Mike