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Discussion Starter #1
Guys,

I have used my Peake Research tool and have an error: 18 0C 91

The manual says it is:

Table 18,

0C - "PreCat oxygen sensor, Cyl #5-8"
91 - "Fuel control, Cyl #5-8"

Judging from this error code and the imtermittent symptoms, I guess this is a dirty MAF.

Can anyone please confirm this, and also which side the MAF for Cyl#5-8 is - whether it is the LHS or the RHS - when looking at the vehicle from the front?

Is it adviseable to change one MAF or both - my 3rd party warranty company (RAC) have approved only one, so I need to pinpoint which one it is.

Thanks in advance!

Was!
 

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5-8 is called bank 2...... driver side.

Now there maybe a situation where the O2 is failing; two codes for the price of one...and as the result the fuel is being adapted incorrectly...... a simply scan on the GT1 will answer this question.

Take care

Shadowman

Whizzkid11 said:
Guys,

I have used my Peake Research tool and have an error: 18 0C 91

The manual says it is:

Table 18,

0C - "PreCat oxygen sensor, Cyl #5-8"
91 - "Fuel control, Cyl #5-8"

Judging from this error code and the imtermittent symptoms, I guess this is a dirty MAF.

Can anyone please confirm this, and also which side the MAF for Cyl#5-8 is - whether it is the LHS or the RHS - when looking at the vehicle from the front?

Is it adviseable to change one MAF or both - my 3rd party warranty company (RAC) have approved only one, so I need to pinpoint which one it is.

Thanks in advance!

Was!
 

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Discussion Starter #3
shadowman said:
5-8 is called bank 2...... driver side.

Now there maybe a situation where the O2 is failing; two codes for the price of one...and as the result the fuel is being adapted incorrectly...... a simply scan on the GT1 will answer this question.

Take care

Shadowman
Thanks Shadowman...

Silly question.. Drivers side (RHD) or (LHD) ? - sorry I had to ask I am in the UK with a RHD.

Also is it worth swapping out both? or is a single sufficient - under normal/best practices.

GT1? I guess another tool I should invest in?

Thx & rgds

Was!
 

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Sorry..... with the hood/bonnet open and you are staring at the motor it will be your right side......

I would not replace either until I placed the GT1 or ?? INPA on her to confirm....then only replace as required.... there are electrical and sometime they simply act up.

Shadowman

Whizzkid11 said:
Thanks Shadowman...

Silly question.. Drivers side (RHD) or (LHD) ? - sorry I had to ask I am in the UK with a RHD.

Also is it worth swapping out both? or is a single sufficient - under normal/best practices.

GT1? I guess another tool I should invest in?

Thx & rgds

Was!
 

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Discussion Starter #5
shadowman said:
Sorry..... with the hood/bonnet open and you are staring at the motor it will be your right side......

I would not replace either until I placed the GT1 or ?? INPA on her to confirm....then only replace as required.... there are electrical and sometime they simply act up.

Shadowman
Cool - Thanks a lot!
:cheers:
rgds

Was!

PS - the MAFs are now 66K miles old - so prob due a clean as well...

Getting a GT1 on would be near on $300 from BMW - and I have had it checked using another software package - and that pointed towards the MAF as well...
 

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WOW they are pretty proud of that unit...$300.00 just to look at the system condition......

At 60k plus they are worth looking at..... my experience cleaning them has been mixed........ lately I replaced one.....attempted to clean two.... the cleaning process seemed to have failed this last time.......... worked great for a day......and then they gave fits......

Have fun

Shadowman

Whizzkid11 said:
Cool - Thanks a lot!
:cheers:
rgds

Was!

PS - the MAFs are now 66K miles old - so prob due a clean as well...

Getting a GT1 on would be near on $300 from BMW - and I have had it checked using another software package - and that pointed towards the MAF as well...
 

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I had the 'Fuel control' and a whole host of 'misfires' on various cylinders, and replacing both MAF meters sorted the problem, havent had a misfire in about 3months despite continuous hard driving etc.

Cleaning them never produced 100% results and there was always an element of 'chance' in the back of your mind during those critical overtaking manoeuvrers that this sporadic limp-home mode would rear its ugly head.
 

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Discussion Starter #8
Úbermensch said:
I had the 'Fuel control' and a whole host of 'misfires' on various cylinders, and replacing both MAF meters sorted the problem, havent had a misfire in about 3months despite continuous hard driving etc.

Cleaning them never produced 100% results and there was always an element of 'chance' in the back of your mind during those critical overtaking manoeuvrers that this sporadic limp-home mode would rear its ugly head.
Where these misfires around without the engine amanagement light popping up?

I ask because, I the light comes on intermittenlty - will go off and come back on whenever i floor it onto a motorway... was wondering because I have noticed a slight degradation in performance - but not into "Limp mode" at any stage.
 

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Havent had any engine management lights shown, but did notice (what felt like) about 50bhp extra with the new MAF units. The engine was rather growly and rough sounding about mid-range beforehand, and feels more punchy and a lot smoother now.

Ideally, you should try another UK members meters (2-minute transfer job) beforehand just to be sure.
 

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shadowman said:
5-8 is called bank 2...... driver side.

Now there maybe a situation where the O2 is failing; two codes for the price of one...and as the result the fuel is being adapted incorrectly...... a simply scan on the GT1 will answer this question.

Take care

Shadowman
So #1-4 is actually on the passenger side (left side when looking at the engine from the front)? Wow, for some reason I thought it was the opposite, based on instinct. You'd think the driver's side (non-UK) would be banks 1-4 and passenger's would be 5-8. Anyway, I got the Pre-cat O2 sensor error with a catalyst efficiency error for banks cylinders 1-4. I'm thinking of just changing out the pre-cat O2 sensor and seeing if it goes away.
 

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Whizzkid11 said:
Guys,

Judging from this error code and the imtermittent symptoms, I guess this is a dirty MAF.

Can anyone please confirm this, and also which side the MAF for Cyl#5-8 is - whether it is the LHS or the RHS - when looking at the vehicle from the front?

Is it adviseable to change one MAF or both - my 3rd party warranty company (RAC) have approved only one, so I need to pinpoint which one it is.

Was!
It is likely a MAFS problem. A simple way to confirm the error is to swap your left and right MAFS sensors. If a new code is generated showing that #1-4 is bad, you'll know which MAFS is bad (assuming that the SES light comes on regularly).

If the code continues to display #5-8 then either both MAFS are bad OR it could be some other problem... as everyone has said... likely a MAFS problem (especially if you have a 2000 M5).
 

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Discussion Starter #12
BlueBomber said:
It is likely a MAFS problem. A simple way to confirm the error is to swap your left and right MAFS sensors. If a new code is generated showing that #1-4 is bad, you'll know which MAFS is bad (assuming that the SES light comes on regularly).

If the code continues to display #5-8 then either both MAFS are bad OR it could be some other problem... as everyone has said... likely a MAFS problem (especially if you have a 2000 M5).
Thanks Johny,

I'll keep you guys posted - I do have 2 brand new MAFs which I bought while I was out in the US - simply because they are expensive in UK and because I have a 2001 M5 with 66K on the clock - I pretty much expected them to go sometime soon... heads-up thanks to the forum.

However, as the warranty company is covering the cost of replacing the one faulty one - I have to let the garage do the work in order to claim it... :grrrr:

Price-wise each MAF in UK = £210.40 that is close to $400 each...
 

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Personally, I'd swap out the Pre-cat O2 sensor first. It's cheaper, and nearly as easy as the MAF. It does require a jack to get under the car, but it's no big deal.

BMW says your O2 sensors should be replaced at 100k miles. My experience (including 1500 miles of track time) is that they last about 35k.

Swapping the MAFs, left for right, might isolate the fault, but the car has already told you "Hey, I think it's my O2 sensor". Listen first, second guess later.

just my $0.02 US.

-don
 
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