MAF sensor recurring issue- help needed please

[Norris997]

Hi
I have a 2005 986 s the a few months ago felt a bit sluggish, I plugged in an OBD reader and DTC P0102- maf sensor code came back. I couldn't find anything wrong with the wiring so replaced the sensor, and airfilter while I was there, now the same problem has come back with the same DTC, the fault clears but comes straight back when the engine is started.
I was wandering if anyone else has had this problem or could it be a dodgy sensor?
Thanks in advance
Dave

 

[C2dweller]

Have you checked for air leaks on the inlet pipe work - it could be that air is getting in after the MAF?
If the MAF looks visibility dirty after such little use I would advise AOS replacement.
KR Lee

 

[Norris997]

Hi Lee
thanks for your quick reply.
i haven't managed to take it apart yet thanks to the great British bank holiday weather. But last time I did check, I couldn't see any splits and gave a quick whiff of break cleaner over the joints and the engine didn't react to it.
As soon as it stops raining I'll have another look
cheers
Dave

 

[Richard_Hamilton]

Can your OBD2 scanner read the MAF Signal Voltage?

With ignition on, it should read 0.9-1.1V
At idle, it should read 1.2-1.5V

Another check - The mass air flow at idle should read around 16kg/hr.

(Figures are for a 2004 986 - I assume you mean this, not a 2005 987).

 

[Norris997]

Hi Richard
it doesn't read MAF voltage, it reads it in kg/min or something like that.
It reads 0.0 with ignition and 0.25 at idle, and stays fixed whatever the revs.
This was the same fault as in April and when I replaced the sensor the reading changed with the revs.
I can get another sensor on exchange tomorrow but I was wandering if anyone has found if there is anything causing the sensor to fail?

 

[Richard_Hamilton]

0.25kg/min = 15kg/hr, but it should increase progressively with revs. If it isn't, then I would say the MAF is faulty, but I have no idea why. Was it a genuine Bosch MAF? There are a lot of cheap Chinese copies around, which I wouldn't touch with a barge pole. Unusual for a Bosch MAF to fail after such a short time.

 

[Norris997]

Hi
I've double checked the sensor and the OBD reads it as g/s not kg/m. But it is stationary at 0.25 g/s and doesn't change with revs.
The sensor looked clean but I used contact cleaner on the terminal just in case, no change so I'll get a replacement in the morning and report back on here tomorrow
It is a genuine Bosch sensor and is under warranty so I'll just get a replacement.
thanks all for you insight and help

 

[Norris997]

Hi all
just an update: I've replaced the sensor and road tested about 20 miles, job done!
Only thing in the back of my mind is, what is making the sensors fail in the first place? The air filter is clean and no contamination inside the intake pipe.

 

[Motorhead]

Hi Dave,

Good to hear that (hopefully!) you've sorted the problem.

By their nature MAF sensors have to be rugged devices but, like any sensitive electronic component, there's always a possibily of failure.

I believe that it's a hot-wire type so maybe there's a problem with the supply voltage. If it fails again I'd get a diagnostic check to confirm that all's well in that respect.

Jeff

 

[Richard_Hamilton]

Good to hear it is sorted. You were probably just unlucky. As Jeff says, if it fails again, try a scan tool with better capabilities. (BTW, they are hot-film, not hot-wire).

 

[jeffreycrowder]

Hello,
I have just bought a 2005 987 Boxster with 60,000 on the clock.
It has recently been serviced but done little mileage over the past three years, in the order of 1,000 miles.
Two things please, the first is that the yellow engine warning light comes on and stays lit together with a red exclamation mark.
Is this serious as it's colour is red?
To get to the bottom of these warnings I have bought an icarsoft POR11 reader but even though I am technical myself it seems to be confusing.
Is shows rich mixture on the banks of cylinders!
Any advice?
Secondly, I bought a sim card for the PCM unit but the telephone facility still does not respond and all the stuff on the internet does not seem to make the problem any clearer, suggesting having to buy a telephone module from Porsche, etc!
Any advice would be appreciated.
JeffC

 

[Richard_Hamilton]

Welcome Jeffrey!

You really need to get the fault codes from the iCarsoft. I suspect that if it is running rich on one bank, it is probably the oxygen sensor on that bank. It is a bit of a guess without knowing the fault code, which should be in the format Pxxxx.

Are you sure you have the telephone module fitted? It is option 666, which is shown on the VIL in the front of the maintenance book. It is located under the driver's seat - a unit about 9"x6"x2" covered by a black plate.

 

[jeffreycrowder]

Thanks Richard for the prompt response.

I have used the iCarsoft device again and it says all systems are now fine, excepting a brake light bulb failure.
I have reset the system removing the icon from the instrument panel so will wait to see if it stays clear.

I don't have the 666 code showing in the Service manual or the box under the driver's seat so its without the device and why the Sim card doesn't do anything.
I will look for another way of sending/receiving calls hands free.

Thanks for the advice, being a member of the Club obviously pays dividends.

Regards.

 

[BartyB]

Dave, I noticed you mentioned that you cleaned the MAF sensor with brake cleaner. I understand brake and carb cleaners are fairly harsh solvents and can affect the sensor's plastic housing as well as the special coatings used on the film which are applied in order to resist any corrosive chemicals present inside the intake manifold. Isopropyl alcohol or isopropyl alcohol-based MAF sensor cleaners are preferred by automotive electronics technicians for cleaning these sensors and similar electronic components used in vehicles.

The Bosch part number is 0280218055 (for a 2004 Porsche Boxster S with electronic throttle control) BTW.

Edit by moderator: removed copyrighted images

 

[Norris997]

Hi BartyB
I used Brake Cleaner not Fluid to check for air leaks in the intake pipe but used electrical contact cleaner to clean the contacts on the plug to the MAF.
1 week and 250 miles after replacing the sensor and all is well!

 

[BartyB]

I meant brake cleaner... it was late. Brake or carb cleaners shouldn't be used anywhere near the functional parts of a MAF sensor. An electrical contact cleaner (read the label to check that it's isopropyl alcohol based) can be used to clean the functional parts of the sensor not just the external connector pins.

Pleased to hear you seem to have cured the issue.

(Note: Only links to imagess on the Bosch site were provided in my earlier post. Contrary to what the moderator who removed them may think this does not constitute copyright theft or an infringement under European or US IP law. No images were harmed in the making of the post ??)

 

[jeffreycrowder]

Back again, still with the engine warning light, this time checked the OBD codes and shows P2188 and P2190, both current and pending whatever that means.
As it is both banks of cylinders it suggests to me that it is not plugs, coils or anything local to one side of the engine but something prior to the inlets. I replaced the fuel filler cap, it had a broken strap anyway but that has had no effect.
Where do I go next, other than to an expensive service centre?

 

[Motorhead]

Hi Jeff,

I'm not sure but this link might be applicable if the problem recurred after refuelling:

http://www.renntech.org/forums/topic/36180-p2188-and-p2190/

Jeff

 

[Richard_Hamilton]

If it is running rich, it looks like it could be the Tank Venting Valve, MAF, fuel pressure, or (highly unlikely) injectors leaking. Here is the full diagnostic sheet for P2188, which might confuse more than assist! If you can check the FRAU and RKAT values, it will help establish which are the possible fault causes.

P2188
Lambda control adaptation FRAU (lower load range) - below limit value

NOTE
The diagnosis is intended to display a negative deviation of more than 30% (leaning) of the lambda control adaptation in the partial load range (FRAU > 0.7).

Diagnostic conditions
* Mass air flow via hot-film mass air flow meter 40 … 220 kg/h
* Incorrect main filling signal from hot-film mass air flow meter
* Engine load 15 .. 80%
* Engine speed 1,040 ... 4760 rpm
* Oxygen sensing in front of catalytic converter active
* Engine temperature > 55.5 °C
* No tank ventilation
- USA: Time after engine starts 250 … 350 s
- RoW: Time after engine starts 302 … 402 s
* No faults detected for oxygen sensor
* No faults detected for tank vent
* No faults detected for hot-film mass air flow meter

Possible fault causes
* Incorrect main filling signal from hot-film mass air flow meter
* Fuel pressure too high
* Injection valve faulty (dripping)
* Tank vent faulty (does not close completely)

Lambda control adaptation FRAU (lower load range) - above limit value

NOTE
The diagnosis is intended to display a positive deviation of more than 30% (fattening) of the lambda control adaptation in the partial load range (FRAU > 1.3).

Diagnostic conditions
* Engine load 15 .. 80%
* Mass air flow via hot-film mass air flow meter 40 … 220 kg/h
* Engine speed 1,040 ... 4760 rpm
* Oxygen sensing in front of catalytic converter active
* Engine temperature > 55.5 °C
* No tank ventilation
- USA: Time after engine starts 250 … 350 s
- RoW: Time after engine starts 302 … 402 s
* No faults detected for oxygen sensor
* No faults detected for tank vent
* No faults detected for hot-film mass air flow meter

Possible fault causes
* Intake system leaking (secondary air)
* Incorrect main filling signal from hot-film mass air flow meter
* Leak in exhaust system
* Fuel pressure too low
* Fuel injector faulty (stuck)
* Fuel pump delivery too low

Lambda control adaptation RKAT (range near idle speed) - above limit value

NOTE
* The diagnosis is intended to display a positive deviation of more than 6 % (fattening) of the lambda control adaptation in the range near idle speed.
* Opposed adaptation values in connection with misfires indicate that the timing has been changed.

Diagnostic conditions
Mass air flow < 32 kg/h
* Engine speed < 960 rpm
* Oxygen sensing in front of catalytic converter active
* Engine temperature > 55.5 °C
* No tank ventilation
- USA: Time after engine starts 250 … 350 s
- RoW: Time after engine starts 302 … 402 s
* No faults detected for oxygen sensor
* No faults detected for tank vent
* No faults detected for hot-film mass air flow meter

Possible fault causes
* Oil filler cap leaking (secondary air)
* Intake system leaking (secondary air)
* Crankcase ventilation leaking (secondary air)
* Incorrect main filling signal from hot-film mass air flow meter
* Leak in exhaust system
* Tank vent faulty (does not close completely)

Lambda control adaptation RKAT (range near idle speed) - below limit value

NOTE
* The diagnosis is intended to display a negative deviation of more than 6 % (leaning) of the lambda control adaptation in the range near idle speed.
* Opposed adaptation values in connection with misfires indicate that the timing has been changed.

Diagnostic conditions
* Mass air flow < 32 kg/h
* Engine speed < 960 rpm
* Oxygen sensing in front of catalytic converter active
* Engine temperature > 55.5 °C
* No tank ventilation
- USA: Time after engine starts 250 … 350 s
- RoW: Time after engine starts 302 … 402 s
* No faults detected for oxygen sensor
* No faults detected for tank vent
* No faults detected for hot-film mass air flow meter

Possible fault causes
* Incorrect main filling signal from hot-film mass air flow meter
* Fuel pressure too high
* Injection valve mechanically faulty (dripping)
* Tank vent faulty (does not close completely)

 

[jeffreycrowder]

In the good old days it was a carb or perhaps two that needed balancing and gaining access to them under a bonnet was a doddle!
Now it seems you need to be an electronics engineer to understand what is going on and a contortionist to access the sensors, progress in the interests of preventing global warming I suppose.
Looking at the MAF sensor a Bosch video shows a faulty sensor causing fluctuation in the idling, on my car the idling is steady suggesting the MAF is fine.
It starts well, warms up and settles down, very little smoke just a little water vapour. The car's performance is good as is the economy so I would suggest it is not a major issue.
As it is reading that both banks have the fault I guess looking for air leaks might be a good starting place.
Thanks Jeff & Richard.