Technical Altitude Sensor?

[DanGT]

Hi All,

I got my ECU memory checked by a computer as the injection malfunction light keeps coming on. The results showed that the Altitude sensor had an open relay/positive short.

A new one will cost me over £80 and is the size of a match box. The connectors are clean and the car runs fine with no light when it is not even connected.

My first question is...

Do I really need to have it connected?

What is it?

Is it safe to leave it disconnected?

Sounds like it is to do with height above sea level. Not much point when you havent got any mountains close by.

I have it connected at the moment and the light is intermittently coming on, no pattern to it, but really annoying seeing as it only boosts half when it is on.

Any advise is great

Thanks

DanGT.

 

[peterlloyd]

I don't know much about the ECU on your wagon but on mine (SAAB) the ECU ensures that a constant power is produced irrespective of altitude petrol type etc etc. I suspect that the altitude sensor is part of a similar system. The question you need to answer is whether the result of having it disconnected is whether the ECU will assume the car is at altitude or at sea level. If the default is sea level then you should be OK (not guaranteed though) if the default is altitude then the engine will not run efficiently.

On mine at altitude I think the turbo boost is increased at altitude to compensate for less air.



Stilo Active 1.2 5 Door/ Panda 4X4

 

[John H]

If it is what I think it is...
it's the MAP sensor (Manifold Absolute Pressure)

If you leave it disconnected effectively your ECU gets a poor/incorrect/out of expected range signal. When one (or more) of its sensors is wrong the ECU will go into "limited operating strategy" otherwise known as "limp home mode" so it doesn't damage the engine by trying to give full grunt in a way that may be wrong for the current conditions (which aren't being reported to the ECU).

MAP is used for information about how much vacuum there is in the inlet manifold (how hard the engine is working). Also, as it is "absolute pressure", it will help give correct initial guess for mixture when you are up a mountain
Even without mountains atmospheric pressure varies quite a bit - whether or not this variation is enought to worry the ECU I don't know.


This is AIUI and is EAOE.

 

[dave]

if you know what it looks like and where it is go to a scrappy.