Chart A-7, Fuel Cut-Off System Operational Check

Fuel cut relay is supplied B+ by fuse 13 and grounded by ECM driver when in a deceleration mode. ECM senses a deceleration condition from the TPS and an engine RPM signal above 2300 RPM. With the relay open, fuel flow is decreased. Code 42 sets when voltage on driver circuit remains high when commanded low.

Fig 1: Chart A-7, Circuit Wiring Diagram & Flow Chart

Courtesy of GENERAL MOTORS CORP.