The logic module uses this solenoid to switch the MAP sensor input from the manifold to the atmosphere. It does this to take a reading of the barometric pressure so that it can calculate the incoming air density for boost control. The solenoid is momentarily activated at closed throttle, once per closure but no more often than once every three minutes and within a certain engine speed band.
On some engines, this solenoid can cause the engine to "miss" at idle because the computer does not "ignore" the MAP sensor reading when it is sampling the outside barometric pressure. This is simply a software fluke that can be ignored.
When the logic module is turning on or off the solenoid, it momentarily checks the output of the solenoid driver to see if it is responding the way it should. If it does not see about 0V when on (open circuit) or 12V when off (short circuit), a fault code 37 is stored.
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Copyright © 1996-2003 Russ W. Knize.