LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Chevrolet >> 1995 >> Forward Control 7.4 N >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 7.4L >> Trouble Code Charts >> Code 28, Transmission Range Pressure Switch >> Diagnostic Aids
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Aids

Code will set if control module detects one of 2 illegal combinations. Check all connections for good contact. An intermittent may be caused by a poor connection, chaffed wire insulation or a broken wire. Monitor voltage of each terminal while moving related harness connectors. If failure is induced, voltage reading will change.

VALID PSM COMBINATION (4L60-E)

Application A B C
Park Off On Off
Reverse On On Off
Neutral Off On Off
4th Off On On
3rd Off Off On
2nd Off Off Off
1st On Off Off
Illegal On Off On
Illegal On On On
VALID PSM COMBINATION (4L80-E)

Application A B C
Park On Off On
Reverse Off Off On
Neutral On Off On
4th On Off Off
3rd On On Off
2nd On On On
1st Off On On
Illegal Off On Off
Illegal Off Off Off
Fig 1: Code 28 Schematic ("C", "K" & "P" Series) Transmission Range Pressure Switch
G95G27595
Fig 2: Code 28 Schematic ("G" Series) Transmission Range Pressure Switch
G95H27596
Fig 3: Code 28 Schematic (All Models) Transmission Range Pressure Switch
G95E14021