One thing that I really miss having on the X3 35i is a turbo boost gauge. Every turbo-engine car I’ve owned has either had a factory-installed gauge or I’ve installed an Autometer electronic boost/vacuum gauge myself. Getting the required wiring harness for the Autometer gauge installed is not a trivial job, since it means running a cable through the firewall.
Anyway, I thought a way around having to do that on the X3 might be to see if the boost pressure value was available through the OBD-II port. The pressure reading is certainly something the engine control CPU monitors, and many vehicles do allow it to be read out via the OBD-II port. Usually the reading is accessed by checking the MAP (manifold absolute pressure) value. Unfortunately, the X3’s port does not respond to a query for a return of the MAP value.
It may not be there at all, or BMW may supply it only under a special (secret) query request.
Anyway, as long as I was connected to the OBD-II system, I decided to see what WAS available on the X3.
The X3 uses the CAN 11-bit protocol.
Here is a list of the digital values that can be read in real time on a X3 35i using
standard CAN queries:
% engine load
engine coolant temperature (deg. F.)
short term fuel trim
long term fuel trim
RPM (resolution on X3 = 1rpm)
MPH (resolution on X3 0.1 MPH)
timing advance
intake air temperature (resolution 0.1 deg. F.)
mass air flow sensor (g/s)
absolute throttle position (%)
oxygen sensor voltage
run time since last start
distance traveled with check engine light on
fuel pressure
evaporative purge (%)
fuel level (% of full)
number of warm ups since engine check light cleared
distance traveled since engine check light cleared
barometric pressure (ambient only – not MAP)
catalytic converter temperature (deg. F.)
battery voltage
accelerator pedal position (i.e.: more than 1%)
mass air flow (calculated)
instanianeous MPG
average MPG
average gallons per hour
run time (general)
distance (miles)
fuel level (reads to 0.1 gal.)
distance to empty (DTE miles)
time to empty (TTE hours:min)
average MPH (current trip)
average MPG (current trip)
fuel used (current trip)
average gallons/hour
run time (trip)
distance (trip)
distance on oil change
distance to service
There probably are others, but they likely require special BMW coding.
It is interesting and fun to drive around with a monitor connected showing some of those readings in real time. I just wish that the manifold pressure (turbo boost) reading was available.