I've got a bit of a rough idle (5.0 SC) and while I did have a MAF fault code a few weeks ago it hasn't recurred since I changed the air filters.

Looking at the two sensors the voltages they seem to be wildly different - does the -30.8v suggest a dead sensor or could it be in need of cleaning? I know normal voltage should be between 1-4v so I'm thrown by the negative reading. The air flow rates seem to be close on both banks.

I'll try swapping the two sensors over to see if the voltage reading follows but any advice would be much appreciated.

Thanks!

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Given the air flow rate is calculated from the voltage and your air flow rates are similar for both banks then I would ignore the -30V.
It looks like that data PID is not used and is throwing up incorrect data as even a failed sensor should never read -30V.
Easy way to check is the wording of the PID, they should be worded exactly the same across banks except the bank number.
If one PID on one bank is showing the correct data i.e.'Mass air flow sensor 2' then the corresponding PID for bank 1 would be 'Mass air flow sensor 1' whereas your scan tool is saying 'Mass air flow sensor - Bank 1' and showing incorrect data.
It's an error of the scan tool although no tool is infallible, in this case, as said, the g/hr is looking similar between the two so I wouldn't worry.
Just as a note the g/hr of both banks looks to be added together to give the overall g/s of the 'Mass air flow' PID, another indication that both MAF's are reading correctly.
As a very rough rule of thumb at idle the MAF g/s should be roughly equal to the engines displacement in litres, i.e 5 litres = 5g/s at idle. Given it's forced induction it will throw that off slightly and I would expect higher than 5g/s which it is.
Reading at idle of the MAF though is not a definite test as they could be out at higher flow rates. It would throw up other errors though like fueling issues if they were out.

What was the issue with the air filter? Certainly if the filter was blocked it would lead to reduced air flow and also if debris had bypassed the filter and landed on the MAF sensor it would cause misreading and lead to a possible code. Over oiled K&N type filters are another cause of MAF's reading incorrectly for the same reason as debris, the oil ends up on the sensor.

Thanks very much for the reply that's very helpful.

I just tried swapping over the MAFs to see if the voltage reading moved with it but it didn't so I suspect it could be the ECU mis-reporting as two different readers have given the same naming/reading.

The original restricted performance/MAF fault code occurred a few weeks ago and following some advice rather than replace the sensor I checked the air filters which I found to be very dirty so replaced them and I haven't had a MAF fault code or restricted performance since then.

I've just cleaned both MAF sensors with MAF cleaner and although I can still feel a little roughness in the idle I think it might have helped a bit. Will wait until I've had a proper drive before I'm sure if that has helped.

I've read about someone else with a rough idle resetting the engine PCM adaptions but not sure if that's advisable or not?

I would check the fuel trims and see what they are reading.
A suddenly clean air filter after being dirty would mean the learnt fuel trims are now going to be out but it will re-learn over time, might take about tanks worth of fuel and driving to re-learn the majority of the blocks.
You can re-set the fuel trims back to zero by disconnecting the battery for about 5 minutes, it'll still take the same time to re-learn though.

The adaptions you don't really want to fiddle with are the gearbox.

Thanks very much that makes sense I hadn’t considered factoring in re-learning.

I did have a look at the fuel trims but can’t remember the values so will check again and report back tomorrow.

I saw there is an engine management adaption reset on the IID tool - do you know if that would be equivalent to unplugging the battery?

Thanks again

These are the fuel trim readings at a cold idle.

Thanks again for your advice

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