TD5 - Absolute air pressure sensor fault

[Chris77]

Hello
1999 discovery TD5 auto , 230 thou on the clock .
Repeatedly shows absolute air pressure fault , logged . Are these prone to failure ? are they important to the running , manual implies its used for boost pressure reference etc .
May have to replace it as is seems sluggish and high fuel consumption , 11.5 to 12l/100km ( stock as a rock and not driven hard ) . ie I only get 630 ish km to a tank , was hoping for something more like 800 .

Anyone else had this fault , what was the fix ?
Thanks

Chris

[justinc]

Yes they are prone to failure, quite rare though. Be warned a new one is disproportionately expensive:mad:

JC

[Chris77]

Great , just surfed the net , they are spendy .

Has anyone driven with it disconnected to see the difference in performance ? Will try it but was wondering what to expect . Obviously no change means its stuffed but it may only be faulting at odd spots , ie high rpm and may not be worth worrying about .

Need a really long extension lead so I can drive down the road with the laptop and see when it faults .

Thanks

Chris

[Redback]

Great , just surfed the net , they are spendy .

Has anyone driven with it disconnected to see the difference in performance ? Will try it but was wondering what to expect . Obviously no change means its stuffed but it may only be faulting at odd spots , ie high rpm and may not be worth worrying about .

Need a really long extension lead so I can drive down the road with the laptop and see when it faults .

Thanks

Chris

It could send the turbo into overboost, not something I'd do, so be careful.

Baz.

[Fluids]

Hi Chris.

12Km/L with a 95L tank will get you 791km to dry.

630km on a tank is 15L/100Km for 95L used.

15L/100Km is definitley too high. I'm averaging 12L/100Km over the last 33,000km ... on/offroad.

Try cleaning all the sensors first up. The one in the airbox, one in the inlet manifold, and the MAF in the inlet pipe after the airbox. Use some CO Contact cleaner and give all 3 of them a thorough cleaning then retest. When I bought my D2 at 120k and checked these sensors they were all pretty dirty (esp' the one in the inlet manifold which looked like something a smoker hacked up !)

Cheers

[OffTrack]

It could send the turbo into overboost, not something I'd do, so be careful.


A faulty AAP can limit boost to 1 bar so I'm not sure that overboosting is going to be an issue.


In the event of an AAP sensor signal failure any of the following symptoms may be observed:

Altitude compensation inoperative (engine will produce black smoke).
Active boost control inoperative.
Turbocharger boost pressure limited to 1 bar (14.5 lbf.in 2 ).
EGR altitude compensation inoperative.

The MIL will not illuminate in an AAP sensor failure, and the ECM will use a fixed default value from its memory.

Searching for MHK100600 turned up a link to an MGF related site (http://www.mgfcar.de/sensor/index.htm) where this sensor is listed as being used for MAP duties. There was a further link to a site (http://homepage.swissonline.ch/TomsSeven/Navigation2/Map.htm) which has information on diagnosing the MHK100600 on the basis of voltage outputs (http://homepage.swissonline.ch/TomsSeven/Main/MAP_logic.htm). However, I'm not really sure how useful this is going to be given that on the Disco 2the MHK100600 is measuring ambient rather than manifold pressure. This might suggest that the MHK100600 is outputting 0.5V at sea level then dropping as altitude increases?