Abstract: A method of operating a vehicle having a friction braking system and a regenerative braking system is presented here. The method determines a regenerative torque capacity, calculates a desired regenerative torque amount for the braking system, detects that the desired regenerative torque amount exceeds the regenerative torque capacity by at least a threshold amount, and controls actuation of the friction braking system in response to the detecting. Another operating method determines a coastdown torque capability of the vehicle, calculates a desired coastdown torque amount, detects that the desired coastdown torque amount exceeds the coastdown torque capability by at least a threshold amount, and controls actuation of the friction braking system in response to the detecting.

Abstract: A method of operating a vehicle having a friction braking system and a regenerative braking system is presented here. The method determines a regenerative torque capacity, calculates a desired regenerative torque amount for the braking system, detects that the desired regenerative torque amount exceeds the regenerative torque capacity by at least a threshold amount, and controls actuation of the friction braking system in response to the detecting. Another operating method determines a coastdown torque capability of the vehicle, calculates a desired coastdown torque amount, detects that the desired coastdown torque amount exceeds the coastdown torque capability by at least a threshold amount, and controls actuation of the friction braking system in response to the detecting.

Abstract: A fuel vapor canister is purged by admitting fuel vapor from the canister to the vehicle engine under control of a solenoid valve, the duty cycle of the valve being controlled to optimize the purge rate. Closed loop fuel correction and block learn fuel correction factors developed by the fuel control system are used to update a learned purge duty cycle which is stored in a keep-alive memory.

Abstract: A method for determining barometric pressure uses a manifold pressure sensor for measuring the manifold absolute pressure. A pressure drop between the atomosphere and the intake manifold is determined by utilizing stored lookup tables based on measured values of throttle angle and engine speed. Barometric pressure is then determined by summing the manifold absolute pressure and the pressure drop.

Abstract: Potentially damaging operation of a viscous converter clutch (VCC) is detected in relation to the slippage thereacross. The slippage is compared with a reference slip value indicative of excessive VCC slippage to develop a net overslip indicator. The value of the net overslip indicator changes in the direction of a first limit value so long as the detected slip is at least as great as the reference slip, and in the direction of a second limit value so long as the detected slip is less than the reference slip. When the net overslip indicator reaches the first limit value, the friction clutch is disengaged to release the VCC. According to a first embodiment, the transmission fluid temperature at the time of such deactivation is measured and stored, and the VCC is reactivated when transmission fluid temperature falls below the stored temperature, assuming other criteria for activation are also met.