lb7 map sensor

S

sprowzms

New member
Joined
Mar 25, 2011
Messages
25
i have a 03 gmc when i have efi live scan tool monitoring the map sensor it is reading 14.4 at a idle. i changed the sensor with 3 others and still same results.if i un plug it it then reads 5 or 6. the truck is low on power at low boost. once the boost is past 14.4 the truck starts making good power and then the sensor starts reading like normal but will not go below 14.4.any ideas would be a help.i traced all wires to the ecm and i have a connection with no shorts to ground or to other connections.
 
The DURAMAX does not use a MAP sensor per say, it uses a boost pressure sensor mounted to the intake and a seperate atmospheric pressure sensor that is mounted on the exterior of the engine with nothing hooked to it. And the 14.4 reading is atmospheric pressure. At sea level a MAP sensor, boost sensor, or atmospheric pressure sensor will read atmospheric or 14.7 PSI which is what air pressure is at sea level. As you go up in altitude teh pressure reading will go down at rest due to the lower air pressure. The sensors all read in absolute, so the raw data stream will read atmospheric or plus boost if it is teh boost pressure sensor. And the LB7 basically only uses boost pressure for emissions monitoring as it doesn't use the boost for fueling. It does use the atmospheric pressure sensor for timing tables and max fueling though. If you are having a fueling delay, look at teh MAF sensor is it does control how much fuel it gets.
 
awesome.i sure appreciate the advice and clarification.
next question if you don't mind. when i try to copy the stock tune with efi live it goes through some steps but it fails every time from a boot loader rejection. but the truck came with a ppe programmer that will work fine loading and unloading tunes.
 
You must log in or register to reply here.
Top