LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 9 (Engine Controls - Tests W/Codes - Transmission) >> Component Check Charts >> Code 28, Pressure Switch Manifold Fault >> Diagnostic Aids

Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 24 other vehicles, including the 1992 GMC Yukon, 1992 GMC Vandura Special, 1992 GMC Vandura, 1992 GMC Value Van, and 1992 GMC Suburban. However, it is still accessible from the selected car via links, so may be relevant.

Code 28 will set if PCM/TCM detects one of 2 "illegal" PSM combinations. See VALID PSM COMBINATION  for various combinations. Check pass-thru connector for good contact.

VALID PSM COMBINATION CHART

Application A B C
Park 12 0 12
Reverse 0 0 12
Neutral 12 0 12
4th 12 0 0
3rd 12 12 0
2nd 12 12 12
1st 0 12 12
Illegal 0 12 0
Illegal 0 0 0
Fig 1: CODE 28, Schematic, Pressure Switch Manifold Fault
G91B13673Courtesy of GENERAL MOTORS CORP.
Fig 2: CODE 28, Flow Chart, Pressure Switch Manifold Fault
G91C13674Courtesy of GENERAL MOTORS CORP.
scientia non olet · About LEMON Manuals