GM > Engine > Fuel Control > COT, Lean Cruise

Catalytic Converter Protection (COT)
The VCM contains mechanisms to estimate the catalytic converter temperature and provide additional fuel enrichment to decrease exhaust oxygen content if over temperature conditions are detected.

Displacement On Demand


RPM Thresholds Vacuum Thresholds Timers Max V4 Time Oil Aeration

Lean Cruise Mode
During light throttle cruise operation the VCM has capability to lean out fuel mixture and advance timing to enhance fuel economy. There are a number of threshold tests that must be met in order for Lean Cruise to come into operation. Note, most code versions have this feature disabled. Lean Cruise is not allowed on any OBDII vehicle operated in the US.