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.

• Enabled: Master enable/disable for this feature
• Enable ECT:
• Max Enrichment: Maximum allowed enrichment due to COT protection. This value is a Fuel/Air multiplier on current commanded AFR. Eg. current AFR is 13.0 and Max Enrichment is 1.1 then the resulting AFR is 13.0/1.1 or 11.81
• Min Enrichment: Minimum allowed enrichment due to COT protection.
• Temperature Thresholds: If these thresholds are exceeded the VCM will enable the Converter Over Temperature (COT) protection feature and provide additional enrichment.
• Enrichment Rate vs. Temp Delta: Rate at which fuel is added during COT operation up to Max Enrichment.
• Air Fuel Ratio:

  
  

• COT Adder Max: Maximum value of the equivalence ratio adder due to COT.
• COT Adder Min: Minimum value of the equivalence ratio adder due to COT.

Displacement On Demand

General

• DOD Enable: Master enable/disable for Displacement on Demand(DOD).
• DOD Enable ERT: Minimum engine run time before DOD can enable.
• DOD Enable VSS: Minimum vehicle speed before DOD can enable.
• DOD Enable ECT: Minimum engine coolant temp before DOD can enable.
• DOD Enable ECT Hysteresis: Hysteresis value for Enable ECT.
• DOD Disable RPM: DOD is disabled if RPM is above this value.
• DOD Disable RPM Hysteresis: DOD is disabled if RPM is above this value, hysteresis value.
• DOD TPS Max: TPS must be below this for DOD to enable.
• DOD TPS Max Hyst: Hysteresis value for TPS Max.
• DOD TPS Delta Max: TPS change(12.5ms) must be below this for DOD to enable(12.5ms).

• DOD Minimum RPM: Below this RPM, V4 mode will disable
• DOD Maximum RPM: Above this RPM, V4 mode will disable
• DOD RPM Min Hysteresis: Hysteresis value for DOD Minimum RPM table
• DOD RPM Max Hysteresis: Hysteresis value for DOD Maximum RPM table

• DOD Enable Vacuum: Engine Vacuum level must be above this to allow switch from V8 to V4 mode.
• DOD Disable Vacuum: If in V4 mode, Vacuum level below this will force a return to V8 mode.
• DOD Vacuum Ignore: When V4 mode is enabled the ECM will delay this long before checking the disable vacuum limits.

• DOD Enable Delay: Transition delay between V8 and V4 mode.
• DOD Disable Delay: Transition delay between V4 and V8 mode.
• DOD Min V8 Time: Minimum time for V8 mode to be active before V4 mode can activate.
• DOD Fuel Cut Delay: Delay time after a non-DOD fuel cutoff event before DOD can enable.

• DOD Max V4 Time Lower: After this time in V4 mode, vacuum delta disable checks are made.
• DOD Max V4 Upper: Maximum allowed time in V4 mode.
• DOD Vacuum Delta Pos: When Max V4 Time Lower is exceeded, change in vacuum(12.5ms) exceeding this will disable V4 mode.
• DOD Vacuum Delta Neg: When Max V4 Time Lower is exceeded, change in vacuum(12.5ms) exceeding this will disable V4 mode.
• DOD Enable Delay Max V4: DOD will not re-enable for this amount of time after it has been disabled for exceeding the max time in V4 mode conditions

• DOD Oil Aeration RPM: To protect the engine oil, DOD is disabled if RPM is above this value for DOD Oil Aeration Time.
• DOD Oil Aeration Time: RPM must exceed the Protect RPM for a total of this much time to activate oil protect mode.
• DOD Oil Aeration Reset RPM: DOD will not enable again until RPM is below this value when oil proect is activated.
• DOD Oil Aeration Reset Time: RPM must be below the Reset RPM for a total of this much time to reset oil protect mode.

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.

• Enable Speed: Speed to enable Lean Cruise.
• Disable Speed: Speed to disable Lean Cruise.
• Enable Delay: Engine Run time delay before enabling Lean Cruise
• Moving Enable Delay: Vehicle must have been moving (ie. MPH > 0) for this time before Lean Cruise is enabled.
• Lean Cruise F/A Subtractor vs. RPM vs. Cyl Air: This value is how much fuel is subtracted from the Closed Loop Fuel/Air Ratio to lean out the mixture. Eg. if the value is 0.1 and the current F/A Ratio is 1.0 then the resulting Fuel/Air Multiplier is 0.9 or 14.7/0.9 = 16.33 AFR
• Lean Cruise F/A Subtractor Mutl vs. ECT: This value multiplies the F/A Subtractor value before it is subtracted from the F/A ratio. It is used to enable, partially enable or disable the feature with respect to Engine Coolant Temp. A value of 1.0 is enable full, a value between 1.0 and 0.0 is a partial enable and 0.0 is disable.
• F/A Subtractor Leanout Rate: The rate that fuel is subtracted to meet the desired Lean Cruise AFR.