306 Automatic Transmissions and Transaxles Copyright by Goodheart-Willcox Co., Inc. The computer also provides diagnostic outputs in the form of dashboard warning lights and a diagnostic connec- tor. The control module saves information about the system defects in the form of trouble codes. Trouble codes are a series of numbers and, on OBD II systems, letters that cor- respond to a specific system defect. The technician must use a scan tool to retrieve trouble codes Transmission and transaxle solenoid functions include line pressure control, lockup clutch control, shift control, and shift cushioning. Most shift control solenoids are multi-shift types that control some valves directly and oth- ers indirectly. Some transmissions have dedicated solenoids that directly control each shift valve. The pressure development, shifting, and other func- tions of modern transmissions and transaxles are fully controlled by the ECM. Interaction of the solenoids and the hydraulic components of the transmission selects the correct gear and applies the converter clutch. Many ECMs control overall pressures and sometimes shift feel. Some transmis- sions have partial electronic shift controls. These are usually found on older three-speed transmissions that have been updated to add a fourth gear. CVT ratios are controlled by the ECM through valves that control the movement of the drive pulley. A manual shift program allows the driver to manually change gear ratios on an electronically controlled transmis- sion or transaxle. Review Questions—Chapter 12 Answer the following questions using the information provided in this chapter. 1. What two valves are not used on a completely elec- tronic transmission? Matching Match the input sensor with its description. 2. Sliding contact that moves along a resistor wire. _____ 3. Creates an AC signal. _____ 4. Pruduces electricity through a chemical reaction. _____ 5. Uses piezoelectric crystal to produce voltage. _____ 6. What are the three main types of MAF sensor? 7. Which of the following sensors uses chemical action to produce electricity? (A) Speed sensor. (B) Oxygen sensor. (C) MAP sensor. (D) Th rottle position sensor. 8. What are the two main external components of the ECM self-diagnostic system? 9. A solenoid’s ratio of on to off is called its _____ _____. 10. How many shift valves are operated by a dedicated sole- noid? Note: Refer to Figures 12-29 through 12-40 to answer questions 11–20. For the following gears, state whether the solenoids are on (energized) or off (de-energized). Solenoid Solenoid A B 11. Neutral _____ _____ 12. Drive first gear _____ _____ 13. Drive second gear _____ _____ 14. Drive third gear _____ _____ 15. Drive fourth gear _____ _____ 16. Manual second _____ _____ 17. Reverse _____ _____ 18. Why is the low reverse clutch piston applied in Park? 19. Downshifts on this transmission are controlled by the _____. 20. What gears are available in Manual Second gear? Note: Refer to Figures 12-41 through 12-44 to answer the following questions 21–25. For the following gears, state whether the solenoids are on (energized) or off (de-energized). Solenoid Solenoid Solenoid 1 2 3 21. Overdrive first gear _____ _____ _____ 22. Overdrive second gear _____ _____ _____ 23. Overdrive third gear _____ _____ _____ 24. Overdrive fourth gear _____ _____ _____ 25. In the above transaxle, when the shift selector is in the drive position instead of overdrive, the forward clutch is applied to provide engine braking. What is the differ- ence in the status of the solenoids (on or off)? (A) Speed sensor. (B) Oxygen sensor. (C) MAP sensor. (D) Th rottle position sensor.