Diagnostic Aids

DTC 87 will set when transmission commanded gear is 3rd or 4th and transmission is mechanically in 1st or 2nd gear. DTC 81 is used to detect a solenoid "B" (2-3 shift solenoid) circuit malfunction.

Fig 1: DTC 87 Schematic - 1994 Diesel

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC 87 Schematic - 1994 Gasoline

Courtesy of GENERAL MOTORS CORP.

Fig 3: DTC 87 Flow Chart - 1994

Courtesy of GENERAL MOTORS CORP.