Chapter 12 Electronic Control Systems 305 Copyright by Goodheart-Willcox Co., Inc. Figure 12-49. A typical shift lever used with a manual shift pro- gram. Most manual shift programs are used with floor shifters. (Volkswagen) M-program - manual up-shifts - manual down-shifts XE-program S-program + – P R N D Figure 12-50. This illustration shows how a typical manual shift program shift lever operates. Note that three different shift pro- grams are available: normal shifting (XE), performance shift- ing (S), and manual shifting (M). (ZF) perfor mance shifts (S program), providing fully automatic shifts that occur at higher engine speeds. The electronic shift control system will ignore a manual shift command that would result in engine or transmission damage. For instance, the control system will neither allow the driver to shift into first gear when the vehicle is traveling at a high rate of speed, nor will it allow a shift into overdrive until a certain speed is reached. Manual shifting programs have many names, depending on the manufacturer. However, the general design of all manual shift programs is similar. Almost all modern manual shift programs make use of a floor- or console-mounted shift lever. Summary On all vehicles made during the last decade, some or all transmission shifts and other functions are made by electri- cal solenoids controlled by the computer, called the ECM. Various sensors monitor engine speed and torque require- ments, other engine and vehicle condition, and transmis- sion pressures and temperatures. Using these inputs, the ECM operates electrical sole- noids to control transmission operation. Solenoids control gearshifts and converter clutch apply, and sometimes line pressures, shift feel, and detent operation. The sensors, ECM, and solenoids replace the governor and throttle valves used to move the shift valves on older transmissions. Some input sensors are located in the transmission to monitor transmission operation. These sensors monitor pressures to determine the transmission gear, and fluid tem- perature sensors. Main shift control sensors are the sensors for throttle position and vehicle speed. Some transmissions and transaxles have an input speed sensor that tells the ECM how fast the input shaft is turning. Other input sensors inform the ECM of engine tem- perature, manifold air pressure, barometric pressure, and engine speed. Some ECMs use input from a mass air-flow sensor and one or more oxygen sensors. Other vehicle inputs to the ECM include the charging system voltage, the opera- tion of the ABS or traction control system, and whether the air conditioner is on. The ECM is composed of many small electronic com- ponents. The entire ECM must be replaced if any electronic part fails. The CPU makes the output decisions based on inputs. The memory is the storage place for information. The two main types of memory are read-only memory (ROM) and random access memory (RAM). ROM contains permanent information installed at the factory. RAM is nonpermanent, or volatile, memory. It changes as operating conditions change. Output devices consist of solenoids installed on the transmission or transaxle valve body. The solenoids operate check balls that act as shift valves, or indirectly move con- ventional shift valves by opening or closing pressure pas- sages. Solenoids may also control line pressure and shift feel. Some transmissions have a solenoid that provides governor pressure. Depending on their use, solenoids can be on or off for long periods, or may be pulsed many times per second. The input sensors, ECM, and solenoids create a control loop that is constantly reacting to changes in operating con- ditions to provide the proper pressures and gear ratio.