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Home >> Buick >> 1995 >> LeSabre Custom >> Repair and Diagnosis >> External Pages >> Different car >> Section 5 (Engine Controls - Tests W/Codes) >> ECM/Pcm Code Charts >> Code P1257, Boost Control Problem (VIN 1) >> Circuit Description
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Circuit Description

WARNING: This page is about a different car, the 1995 Oldsmobile Ninety-Eight and 1995 Buick Park Avenue. However, it is still accessible from the selected car via links, so may be relevant.

Under most conditions, PCM commands boost control solenoid to operate at a 100 percent duty cycle (on) to allow full intake boost pressure upon demand. However, if reverse gear is selected, PCM detects rapid deceleration or engine load is extremely high, reduced boost is desired. Under these conditions, PCM commands boost control solenoid to operate at a zero percent duty cycle (off), which opens by-pass valve to reduce boost pressure by recirculating it back through supercharger inlet.