What Does This Mean

[cai]

I bought a diagnostic tool for my 1999 - 740i since I was having problems with the "service engine soon" message coming on for the last 2 months. Last night the tool cleared the message and also gave a code number - Table 0F - code A4 "ambient pressure sensor".

1.- Does anyone know what this means?
2.- Where is this sensor?
3.- Is this an indication of a lean or rich mixture?
4.- What ambient is it reading? I have had the car for 2 years at the same location, with no sea level changes.

I installed a K&N air filter last week in anticipation of air intake problems, but the message still keeps coming on.

Thank you.

[cai]

My previous diagnosis with the resetting tool was incomplete. I have done a new diagnosis and have the following information:

Table 0F in the tool manual:

Hexadecimal tool code BMW dealer code
A4 - ambient pressure sensor 164
1A - mix control, off idle cylinders # 1-4 26
1B - mix control, off idle cylinders # 5-8 27

The dealer calls the codes 1A and 1B:
code #26 - multiplicative mixture adaptation bank 1, control limit reached
code #27 - multiplicative mixture adaptation bank 2, control limit reached
code #164 - atmosphere pressure sensor

This could be a sticky PCV valve. Does anyone know if these cars have a PCV valve that could be clogging or sticking and where it is?

Thank you.