DeVille V8-4.6L VIN Y (1998)
Powertrain Control Module: Description and Operation
Torque Management
Description
Torque Management is a function of the PCM that reduces engine power under certain conditions. Torque management is performed for three reasons:
^
To prevent overstress of powertrain components.
^
To limit engine power when brakes are applied.
^
To prevent damage to the vehicle during certain abusive maneuvers.
Operation
The PCM uses manifold vacuum, intake air temperature, spark retard, engine speed, engine coolant temperature, A/C clutch status, and EGR valve
position to calculate engine output torque. It then looks at torque converter status, transaxle gear ratio, and brake switch inputs and determines if any
torque reduction is required. If torque reduction is required, the PCM retards spark as appropriate to reduce engine torque output. In the case of abusive
maneuvers, the PCM may also shut off fuel to certain cylinders to reduce engine power.
There are five instances when engine power reduction is likely to be experienced
^
During transaxle upshifts and downshifts.
^
Heavy acceleration from a standing start.
^
If brakes are applied with moderate to heavy throttle (input supplied by the Extended Travel Brake switch).
^
When the driver is performing stress-inducing (abusive) maneuvers such as shifting into gear at high throttle angles.
In the first two instances, the driver is unlikely to even notice the torque management actions. In the other cases, engine power output will be moderate at
full throttle.
When the PCM determines that engine power reduction is required, it calculates the amount of spark retard necessary to reduce power by the desired
amount. This spark retard is then subtracted from the current spark advance. In the case of abusive maneuvers, the fuel injectors for cylinders 1, 4, 6, and
7 will also be disabled for a period of time.
