Diagnostic Aids

Check all connections, especially those at the transmission pass-thru connector. If code is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section. Some slight TCC slippage is normal. 3-2 control solenoid feedback normally oscillates on/off when the duty cycle is applied.

Fig 1: CODE 66, Schematic, 3-2 Control Solenoid Circuit Fault

Courtesy of GENERAL MOTORS CORP.

Fig 2: CODE 66, Flowchart, 3-2 Control Solenoid Circuit Fault

Courtesy of GENERAL MOTORS CORP.