Note On Intermittents

If code sets intermittently, problem may be caused by poor electrical connections. When checking lift/dive signal, ignition must be cycled off and on twice for code to reset. If engine is cranked with transmission in gear, SSS control module shuts off, but PCM does not shut off. Under this condition, the lift/dive "handshake" is not performed, possibly setting a code.

"Handshake" may also be monitored while in ECM OUTPUTS, CYCLE ALL (EO99) mode. The EO99 value should go low and high, and the voltage at the SSS control module should go low and high. A high-to-low voltage change should also occur when the accelerator pedal is depressed quickly.

Fig 1: CODE 31 Schematic

Courtesy of GENERAL MOTORS CORP.

Fig 2: CODE 31 Flow Chart

Courtesy of GENERAL MOTORS CORP.