MAP Operation Question
 

I can disconnect the electrical connector, go for a drive and read boost on my SCT Livewire...???? Where is this coming from?:ohno:

I can re connect the electrical connector, take off the boost hose and see no boost.:madd:

My understanding is that the MAP is responsible for reporting boost so how does it work when disconnected?

Well
 

unless you have a boost line just for the livewire thats a good question.

if you have a boost hose, its reading boost to the livewire... (like my boost guage... works w/o any electircal cause its a mechanical guage with teh boost "hose"/tube attachted to it....

by disconnecting the "electrical connector" - that means the OBDII port? The MAP sensor will read the boost and does "report" the #, so when its disconnected, you will have to rely on a boost tube.. otherwise you woudl'nt read any boost

I apologize. You guys aren't familiar with the Livewire. It's only connection to the truck is via the OBD2 port and it's own EGT input. That's all. There's no additional boost input from anywhere else.

The electrical connection I referred to is the actual MAP harness under the hood. I disconnected that and can still read boost.

So how does an unpowered MAP sensor read to the PCM and then ultimately show up on Livewire??

-- I have some good stumpers, eh?--:c:

ahhh, gotcha -- now tha tI have no idear... unless ... nah, no clue..

I think this is one for Jon...

The PCM might be taking something from the Exhaust backpressure sender, and making something up due to a lack of info coming from the MAP sensor. Are you sure you are disconnecting the MAP sensor?