Intermittent P0100

[dracc]

Hi all!

I've been having troubles with my 1.9TiD for quite some time now.
CEL turns on every now and then and the car goes into limp home mode after a few moments. My OBDII reader tells me it's the MAF (Error code P0100).
Restarting the car makes the limp home mode deactivate and it runs better (not fully well) for a while. CEL stays on though.

Resetting the error code when the engine is cold makes it run perfect for about 25-35km until the CEL turns on again.
Resetting the error when the engine is warm has little to no effect - sometimes it stays off for another kilometer but most of the time it turns back on after a few seconds if not immediately.

I've tried replacing the MAF sensor (twice), EGR valve, Intercooler and repaired a crack in the exhaust manifold.
Still the problem persists.

Does anyone here have any suggestions on what I could try next?

[sgould]

I'm not 100% familiar with modern diesels, but have you got a small air leak. If the car finds an anomaly between the MAF reading and the calculation of other sensors, it gets upset.  These leaks could be a very small crack.  Or there could be corrosion in a connector in the wires to and from the MAF.

[carrera]

I have reviewed the diagnostic approach for that fault code.

Essentially is appears to be either the MAF sensor itself or the wiring to it. As you have replaced the sensor twice, then you need to look at the wiring.

Check for voltage at pin 1 and wiggle the harness to make sure there is no break

Check the earth route via pin 2

Measure the voltage on pin 3- should be around 5v +/-0.2v

Same for pin 4

I hope that makes sense and you have a meter that you can use

If all that checks out the conclusion is to change the MAF sensor,which isn't the problem

I hope that helps

[dracc]

Thanks a lot for the replies!

I forgot to mention that I had one of the SAAB specialist workshops here in Sweden ("Holmgrens Bil", a former retailer) have a troubleshooting session (or three actually) and they claim that they have measured the harness with no signs of problems there.
I guess I also should have mentioned that P2227 (a bit unsure on that one number) pops up once in a blue moon, something my OBDII reader claims has to do with a leak in inlet port A.

I should probably investigate the hoses and pipes a bit more thoroughly.

[carrera]

OK,so P2227 is a more specific MAF type fault which is described as a difference between boost pressure and atmospheric pressure of 0.15 bar

As I don't have a 1.9 diesel it's difficult to be sure but is seems that the issue is comparative readings between the MAF and the second sensor, described as "charge air pressure sensor"

Diagnostics is to  similar to the MAF and relies on measuring voltage / wiggling wires on that part of the harness to test for breaks. That is after using Tech 2 to measure the pressure being measured at the pressure sensor

Here's the location extract from WIS

I would be tempted to carefully examine the intake system between the MAF and the secondary sensor for potential leaks. Maybe there is a small crack which only gets exposed in certain conditions (that would include the intercooler itself)

I think my blue Aero actually came into the UK from Holmgrens Bil in Gothenburg. I know it was supplied from Gothenburg and seem to remember passing the dealer previously on the E6 on my way back to the ferry

Lycka til !

[sgould]

Is the sensor on the manifold the one that gets badly fouled up and needs a good clean?  Might be worth unscrewing and having a look.  I haven't seen one for ages, but I believe that they are a bit fragile and need to be soaked in something to soften the gunk.  Either that or replace.

[carrera]

I think so - it's highlighted in purple on the screen dump above

[dracc]

I'm sorry for misleading you earlier. The error code popped up again, turns out it is P2279 and not P2227.   

[carrera]

This may be an additional code to the p2227

described as "mass air flow lower than expected"

It basically tells you to look for air leaks on the intake side from air filter through to inlet manifold and contamination of the MAF

Then with Tech 2 check EGR operation, vacuum on the boost control valve, the vacuum hose itself and finally if all that is OK the conclusion is the VNT mechanism on the turbo

[dracc]

I went out and took a glance under the hood. Turns out that the swirl flap bar has come loose (again).
Is this a sign that the intake manifold need be replaced or are there other culprits with a higher probability of being the cause?

[aerojon]

the MAP sensor get absolutely covered in carbon crud it stops providing accurate data to the ecu..Pics give an idea of how bad..