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Home >> Buick >> 1995 >> LeSabre Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> ECM/Pcm Code Charts >> DTC P1257: Boost Control Problem - VIN 1 >> Test Description
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Test Description

NOTE: Test numbers refer to numbers on diagnostic chart.
  1. Circuit shorted to ground will keep by-pass valve closed when PCM is commanding it open, possibly causing an overboost condition during high engine load situations.
  2. No inlet vacuum to by-pass valve actuator may cause by-pass valve to remain closed during deceleration. This condition may be perceived as a sail-on, possibly accompanied by a rough idle.
Fig 1: Code P1257 Schematic (3.8L (VIN 1)) Boost Control Problem
G94B34729
Fig 2: Code P1257 Diagnostic Flow Chart (3.8L (VIN 1)) Boost Control Problem
G94A35220