Who here can interpret a scan?

[M5V8 337]

Had the car scanned at BMW.

They were kind enough to leave me with the printout.

The mechanic wasn't sure if my issue was o2 or MAF sensors. He stated it shows o2 sensor faults but though this is more likely to be worn MAFs

It states mix too rich

Volt MAF 1.12 & 1.10

After cat o2 sensor status "ageing"

Voltage before cat .78v & .52v

There plenty more info here. I'm just not sure what's good or off

Help....

[*Glenn* 854]

A scan does not always diagnose the actual fault. The readings you get may be the result of an unmetered fault.

ie: the result of something that is mechanical rather than metered. Air leaks are a prime example for lean oxy fault codes. Leaking injectors and faulty fuel pressure regulators for rich mixture issues. The scan tool is just a tool ... the user needs a brain and diagnosis of the actual fault may take a lot more time than just scanning the vehicle and providing a print out.

[M5V8 337]

Thanks Glenn

Well there isn't really a fault as such. Cars running fine. Just very occasionally the odd low rpm stall.

It's more trying to keep her in top condition. (I'm a little OCD)

How long or how many kms would the MAF sensors expect to start to degrade?

The nice lad at BMW seemed to suspect they might just be on their way out ... And I might pick up some lost power by throwing some new units in.

[HELLBM 1550]

My understanding is that MAF sensors degrade some time before anything will show up in a scan. Try ECS Tuning if you need to get some. I went for the Bosch. The intake air temp sensor is integrated into the MAF which due to location can give a high temp reading to the DME which will in turn affect fuel trim. UFM do a relocation kit. I made my own with a temp sender from M50 or M60 inlet manifold. Pulled the temp back from 40/50C reading to 30/35C reading.

We have been doing some experimenting around the aft S62 oxy sensors and the role they play. With my cat delete I initially went for a sensor delete now I`m going to put them back in due to fuel trim related issues. We are using `spark plug defoulers` to take them out of the exhaust stream thus providing them with a sniff of aft exhuast gase which should in theory help with overall performance..

Any chance you could email me a copy of your scan.

Regards Ray

Edited March 15, 2013 by HELLBM

[M5V8 337]

Well I spent yesterday with CRCs MAF cleaner and a cotton tip.

After spraying the MAF wires and very gentle rubbing I can feel a noticeable improvement in power using the old bum dyno.

I guess I'm not really sure how much is simply the new spark plugs from last wknd or MAF clean yesterday.

Or how long a cleaner MAF unit will prolong the evidential MAF replacement. As a lot of forum chat seems to think cleaning is simply a short term solution.

I just wonder how much difference new MAF units will make. There is was no noticeable dirt or damage on the units.

I think I will keep any eye on the fuel economy on longer trips as this would seem the best judge of mixtures and compare against a MAF replacement in a few months.

Happy to share the scan ill just have to scan it to send you Ray.

I'll try to sort this for you shortly.

[kiwi535 538]

i have read somewhere that the Cam(or is it crank) shaft postion sensors can malfunction too.Wether or not it is related to your scan results i have no idea!

[M5V8 337]

I don't think so. It didn't come up in the scan.

The BMW master tech that came and had a chat only talked about the values from the O2 sensors and how they might be out if the MAF units were not operating correctly.

Or it might just be a particular 02 sensor.

Then obviously offered to take her in for a few days to diagnose further.

I think i'll stick to my plan of replacing the MAF units if the car doesn't show noticeable fuel mileage improvement and i'll try the OBC MAF test to see what they are flowing as per:

http://www.m3torque.co.uk/showthread.php?t=43

Then re-scan.

Edited March 18, 2013 by M5V8

[BreakMyWindow 1874]

There is some good info on m5board.com in regards to testing the MAF's by means of measuring how many litres per hour the car consumes through out the rev range. You can obtain this reading via the secret OBD menu, i think its in one of the first few tests.

If you decide to get new maf's don't go for the vw substitue, not only do u need a special hard to find tool to remove the unit from it's housing, but it will degrade performance. I went down this road in my 540i ( m62tu uses same MAF as the m5) After replacing the substitute vw maf unit with a Bosch one, there was a noticable improvement in response and low down torque, the 540i would now plod along doing 60km/h up a hill with full torque converter lock-up doing about 1100rpm :-) where as before it would change up a gear.

If you have the patience, read through this : http://www.m5board.com/vbulletin/e39-m5-e5...-mafs-work.html

[M5V8 337]

cheers

yes I've already had a little read of that page before I fell asleep.

Great late night reading.

I've already located a place which sells just the genuine bosch MAF units save paying for the full tube as well.

they even give you the tool to remove.

http://www.bimmerzone.com/category/BMW_Performance_MAFS.html

[BreakMyWindow 1874]

As a reference, any one who is needing new MAF's for their E39 540i or M5, I have found a very cheap place for genuine Bosch units via Germany. I paid $315NZD incl shipping for 2 x E39 M5 MAF units in housings.

http://www.maf-shop.com/product_info.php/i...3621433566.html