2. OBJECTIVES After studying Chapter 8, the reader should be able to:
Explain how electronic controls are used for transmission operation.
Identify the major automatic transmission electronic control components.
Describe the relationship between volts, amperes, and ohms.
Explain the circuit required for an electrical system to operate.
Describe the operation of an electronic transmission.

3. INTRODUCTION
FIGURE 8-1 An electronic transmission has electronic sensors and actuators and is integrated electronically with other phases of vehicle operation.

4. INTRODUCTION
Current electronic automatic transmissions are able to provide diagnostic information as well as accurately control:
Shift timing and quality
Mainline pressure
Application and release of apply devices
Apply-device pressures
Clutch-apply fluid volume
Application and release of the torque converter clutch
Ignition timing during shifts

5. INTRODUCTION
FIGURE 8-2 When the transmission control module (TCM) is ready to begin an upshift, it signals the power train control module (PCM) to reduce engine torque. This produces a smoother shift with less wear in the transmission.

6. INTRODUCTION
FIGURE 8-3 The fuzzy logic part of the TMC receives input signals, compares what the driver is doing with the throttle and what the vehicle is doing with normal operation, and adapts shift timing.

7. INTRODUCTION
FIGURE 8-4 This electronic transmission valve body includes four solenoids.

8. BASIC ELECTRICITY
The three measurable aspects of electricity that concern an automotive technician are:
Current flow (amperage),
Electrical pressure (voltage)
Resistance to current flow (ohms).

9. BASIC ELECTRICITY
FIGURE 8-5 If we compare electricity with hydraulics, voltage and pressure (a), current flow and fluid flow (b), and a resistor and orifice (c) are very similar.

10. BASIC ELECTRICITY
FIGURE 8-5 (CONTINUED) If we compare electricity with hydraulics, voltage and pressure (a), current flow and fluid flow (b), and a resistor and orifice (c) are very similar.

11. BASIC ELECTRICITY
FIGURE 8-6 Insulated wires conduct electricity to the lights. The body metal forms the ground circuit to complete the circuit back to the battery. This is shown in a diagram (a) and a schematic (b).

12. BASIC ELECTRICITY
FIGURE 8-7 A series circuit (a) and a parallel circuit (b).

13. BASIC ELECTRICITY
FIGURE 8-8 Wiring schematics use symbols to show the various components. (Courtesy of Chrysler Corporation)

14. BASIC ELECTRICITY System Components Power Source Circuit Protection
Switches
Wiring
Electrical Loads

15. BASIC ELECTRICITY
FIGURE 8-9 This wiring diagram of a transmission with electronic controls for fourth gear (O/D) shows the power source (battery), three fuses for protection, a control switch and two ECUs (electronic control units), two output devices (the O/D solenoid and indicator light), and the wires that connect them.

16. BASIC ELECTRICITY
FIGURE 8-10 Circuit protection can be fuses with tubular or flat-blade connections (a), a circuit breaker (b and c),or a fusible link (d). (Courtesy of Chrysler Corporation)

17. BASIC ELECTRICITY
FIGURE 8-11 This stop light switch is a normally open switch. When the brake pedal is depressed, battery voltage is sent to the ECT ECU. (Courtesy of Toyota Motor Sales USA, Inc.)

18. BASIC ELECTRICITY
FIGURE 8-12 A de-energized relay. Relays use a magnetic coil to either close or open switch contacts. Note that terminals 85 and 86 are for control, terminals 30 to 87 are normally open, and terminals 30 to 87A are normally closed. (Courtesy of Chrysler Corporation)

19. BASIC ELECTRICITY
FIGURE 8-13 Electrical wire is sized by gauge sizes or cross section in millimeters; three American wire gauge (AWG) sizes are shown for comparison (a). Wire colors with tracers are used to identify particular wires (b). (b is courtesy of Chrysler Corporation)

20. BASIC ELECTRICITY
FIGURE 8-14 Transmission solenoids can take different shapes, but they all include an electromagnet and a valve. The style shown in (b) is the most common. (a is courtesy of Chrysler Corporation; b is courtesy of Toyota Motor Sales USA, Inc.)

21. BASIC ELECTRICITY
FIGURE 8-15 A clamping diode is wired parallel to the coil winding (a). It blocks current flow when the switch is closed, but it allows induced current to dissipate when the switch opens (b).

22. BASIC ELECTRONICS
Solid-state electronics is the basis of automotive computers and control modules.
These devices are constructed from diodes, transistors, capacitors, resistors, integrated circuits, and microchips.
Solid-state devices, for all practical purposes, do not wear out because there are no moving parts.
A major difference between electrical and electronic circuits is the quantity of electrical flow.
The current flow in electronic circuits is very small, thus the voltage requirement is low and circuit resistance must be kept to a minimum.

23. BASIC ELECTRONICS
FIGURE 8-16 This PCM receives sensor input (at left) and controls actuators (outputs) inside the transmissions

24. BASIC ELECTRONICS Sensors
The various sensor types (organized by the type of electrical signal) are as follows:
Frequency generators (creates an ac signal with a frequency relative to speed)
Voltage generator (creates a voltage signal that is relative to speed)
Potentiometer or variable resistor (alters the voltage or resistance)
Switches (an on–off signal)
Serial data (an on–off signal coming from another control module)
Thermistor (changes resistance relative to temperature)
Transducer (changes resistance relative to pressure)

25. BASIC ELECTRONICS
FIGURE 8-17 This transmission uses an input (left) and output (right) speed sensor. The sensors generate a signal frequency that is relative to the speeds of the reluctor rings. (Courtesy of Toyota Motor Sales USA, Inc.)

26. BASIC ELECTRONICS
FIGURE 8-18 The speed sensor switch will close as the magnet moves past it (a).It will generate a square wave/on–off signal (b).

27. BASIC ELECTRONICS
FIGURE 8-19 The reluctor tooth will pull the magnetic field across the coil windings as it moves past (a). It will generate a sine wave/AC signal (b).

28. BASIC ELECTRONICS
FIGURE 8-20 An input speed sensor along with an output speed sensor allows the TCM to calculate the gear ratio and determine how long it takes to complete a shift or if there is internal slippage in the gear train. (Courtesy of Chrysler Corporation)

29. BASIC ELECTRONICS
FIGURE 8-21 ATPS (throttle position sensor) is mounted at the throttle body. It provides an electronic signal of the throttle operation to the ECM.

30. BASIC ELECTRONICS
FIGURE 8-22 The ECT (engine coolant temperature) sensor is mounted close to the engine’s thermostat (a). It is a thermistor (b) that provides a coolant temperature signal to the ECM (c and d).

31. BASIC ELECTRONICS
FIGURE 8-23 A transmission fluid temperature sensor can be checked by connecting an ohmmeter to the harness connector terminals (a). The resistance should change as the temperature changes (b).

32. BASIC ELECTRONICS
FIGURE 8-24 This hydraulic circuit shows three fluid pressure switches that signal the TCM when there is pressure in their circuits. (Courtesy of Chrysler Corporation)

33. BASIC ELECTRONICS
FIGURE 8-25 Some systems include an AD (analog–digital) buffer to convert the ac analog speed sensor signal so it can be read by the ECM.

34. BASIC ELECTRONICS
FIGURE 8-26 This MLP (manual lever position) sensor/neutral start switch is mounted at the transmission. It provides a shift lever position signal to the ECM.

35. BASIC ELECTRONICS
FIGURE 8-27 The stop light switch is mounted at the brake pedal. It provides a brake-apply signal to the TCM. (Courtesy of Toyota Motor Sales USA, Inc.)

36. BASIC ELECTRONICS Electronic Transmission Shift Controls
Serial Data
OBD-II
Controller Area Network
Transmission-Based Control Module
Actuators
Shift Solenoids
Shift Solenoid Operation
Pressure Control Solenoids
CVT Electronic Controls

37. BASIC ELECTRONICS
FIGURE 8-28 Power supply for the electrical circuits of a modern vehicle begins at the power distribution center. It usually includes major relays and the fuses. (Courtesy of Chrysler Corporation)

38. BASIC ELECTRONICS
FIGURE 8-29 Solenoid control occurs when the ECM completes the circuit to ground (top) or switches on B+ (bottom). The ground connection is also B-.

39. BASIC ELECTRONICS
FIGURE 8-30 This electrical schematic shows the various inputs and outputs of the transmission control module for a 42LE transaxle. (Courtesy of Chrysler Corporation)

40. BASIC ELECTRONICS
FIGURE 8-31 The scan tool is being plugged into the diagnostic connector (arrow) under the instrument panel. It can read any DTCs, sensor outputs, and operate the solenoids inside the transmission.

41. BASIC ELECTRONICS
FIGURE 8-32 A weathertight connector is used at this pressure switch (a). Opening the latch allows the connector to be removed (b).

42. BASIC ELECTRONICS
FIGURE 8-33 One of the solenoids is wired directly to this internal electrical harness. Note the case connecter near the bottom.

43. BASIC ELECTRONICS
FIGURE 8-34 The CCD (Chrysler Collision Detection) bus allows the BCM (body control module) and PCM (power-train control module) to share information such as the signal from the transaxle output speed sensor. Among other things, this signal is used for the speedometer. (Courtesy of Chrysler Corporation)

44. BASIC ELECTRONICS
FIGURE 8-35 This control solenoid assembly (a) contains four transmission fluid pressure (TFP) switches, a line pressure control (PC) solenoid, four pressure control (PC) solenoids, two shift solenoids (SS), a torque converter clutch (TCC) solenoid, a transmission fluid temperature (TFT) sensor, and the transmission control module (TCM). It also has a vehicle harness connector and connectors to the shift position switch and the input and output speed sensors. A simplified view is also shown (b).

45. BASIC ELECTRONICS
FIGURE 8-36 This solenoid is on. Magnetic force has pulled the plunger to the right. Fluid pressure has moved the metering ball off its seat, and fluid is passing through the valve. (Courtesy of Toyota Motor Sales USA, Inc.)

46. BASIC ELECTRONICS
FIGURE 8-37 The tapered stems are connected to the shift solenoids. When the solenoids are on, they move downward to move the check balls off their seats and also close the vent. (Courtesy of Chrysler Corporation)

47. BASIC ELECTRONICS
FIGURE 8-38 The No. 1 solenoid is on. Fluid pressure is exhausted at the drain, and the 2–3 shift valve is upshifted. The No.2 solenoid is off, so fluid pressure has the 1–2 shift valve in downshift position. (Courtesy of Toyota Motor Sales USA, Inc.)

48. BASIC ELECTRONICS
FIGURE 8-39 The hydraulic diagram of a Toyota A240E transaxle in second gear. Both the No.1 and No.2 solenoids are turned on.

49. BASIC ELECTRONICS
FIGURE 8-40 The valve body for a 41TE transaxle. Note that there are no shift valves. (Courtesy of Chrysler Corporation)

50. BASIC ELECTRONICS
FIGURE 8-41 The hydraulic diagram of a 41TE transaxle in first gear. The shift to second occurs when the 2–4/LR solenoid is turned on to allow pressure to flow to the 2–4 clutch. (Courtesy of Chrysler Corporation)

51. BASIC ELECTRONICS
FIGURE 8-42 The solenoids and pressure switches of this Chrysler transaxle are mounted under the solenoid sound shield on the outside of the transaxle. (Courtesy of Chrysler Corporation)

52. BASIC ELECTRONICS
FIGURE 8-43 Line pressure increases as the duty cycle of the EPC solenoid increases.

53. BASIC ELECTRONICS
FIGURE 8-44 This block diagram shows the relationship between the TCM, electrical actuators, valve body, and hydraulic actuators for a CVT transmission.

54. BASIC ELECTRONICS
FIGURE 8-45 The stepper motor and pulley ratio link with the CVT in low ratio (A). The stepper motor has extended (B), moving the ratio link and ratio control valve; this should cause the primary pulley to become narrower to produce a higher ratio.

55. SUMMARY
Electronic controls are used for more accurate automatic operation of the transmission.
A basic understanding of electricity and electronic devices is essential to understanding and repairing electronically controlled transmissions.
Electronic controls use sensors to monitor various operational inputs that will be used to control the operation of the transmission.

56. SUMMARY
The hydraulic operation of the transmission is controlled by solenoids that are switched to redirect pressurized fluid to move shift valves or change the operational pressures.
The TCM receives the signals from the sensors and operates the solenoids to produce upshifts and downshifts at the proper speed.
CVT transmissions use the same type of logic for transmission control as conventional electronic transmissions.

57. REVIEW QUESTIONS
Electronic control of the automatic transmission provides for accurate control of shift _____ and _____.
Electronic transmissions replace the governor with a _____ _____ _____ and the throttle valve with a _____ _____ _____.
A complete electrical circuit has a _____ source, circuit _____, _____, conductors, and an electrical _____.
Three types of electrical protection devices are _____, _____, and _____.
When the circuit is _____, current will stop flowing.
A _____ controls a switch by electromagnetism.
A _____ controls fluid flow by electromagnetism.

58. REVIEW QUESTIONS
The three major parts that an electronic control system can be divided into are _____, _____, and _____.
Identify the six inputs that an electronically controlled transmission might use for each of these.
Vehicle _____
Input shaft _____
Engine coolant _____
Engine _____
Driver _____
Transmission _____ temperature

59. REVIEW QUESTIONS
A thermistor is a _____ resistor that changes resistance relative to _____.
Identify each of the following abbreviations.
BOO
PRNDL
ECT
MAP
MAF
MLP
PNP
TOT
TSS
TPS
VSS
TCC
ECM
PCM
Good ground connections are essential for proper operation of _____ circuits.

60. REVIEW QUESTIONS
A diagnostic _____ code (DTC) will set if an electrical problem is identified by the electronic control unit (ECU). DTCs can be read with a _____ tool.
Six actuators that are computer controlled are _____, _____, _____, _____, serial data, and _____.
Shift solenoids are controlled by the ECU to control the fluid pressure in the _____ valve circuits.
If both shift solenoids on a typical Toyota transmission are inoperative, what gear will the transmission be in?
If the shift solenoids fail in a Chrysler 41TE transmission, what gear will the transmission be in?
EPC solenoids use _____ _____ to cycle a circuit on and off.
Ramping a torque converter clutch (TCC) solenoid produces a _____ lockup clutch apply.

61. CHAPTER QUIZ
Student A says that it is important to have an understanding of electricity to understand an automatic transmission. Student B says that in most electronically controlled transmissions, the shift valves are controlled by solenoids. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

62. CHAPTER QUIZ
Student A says that it is important to have an understanding of electricity to understand an automatic transmission. Student B says that in most electronically controlled transmissions, the shift valves are controlled by solenoids. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

63. CHAPTER QUIZ 2. Electrical pressure is measured in amperes. ohms.
volts.
watts.

64. CHAPTER QUIZ 2. Electrical pressure is measured in amperes. ohms.
volts.
watts.

65. CHAPTER QUIZ 3. The current flowing through a circuit is measured in
amperes.
ohms.
volts.
watts.

66. CHAPTER QUIZ 3. The current flowing through a circuit is measured in
amperes.
ohms.
volts.
watts.

67. CHAPTER QUIZ
4. The resistance to electrical flow through a component is measured in
amperes.
ohms.
volts.
watts.

68. CHAPTER QUIZ
4. The resistance to electrical flow through a component is measured in
amperes.
ohms.
volts.
watts.

69. CHAPTER QUIZ
5. The controlling unit for an electronically shifted transmission is the
vehicle speed sensor.
TCM.
throttle position sensor.
None of these

70. CHAPTER QUIZ
5. The controlling unit for an electronically shifted transmission is the
vehicle speed sensor.
TCM.
throttle position sensor.
None of these

71. CHAPTER QUIZ
6. A _____ is an electromagnetic device that can be used to control fluid pressure in a hydraulic circuit.
neutral start switch
TCM
Solenoid
vehicle speed sensor

72. CHAPTER QUIZ
6. A _____ is an electromagnetic device that can be used to control fluid pressure in a hydraulic circuit.
neutral start switch
TCM
Solenoid
vehicle speed sensor

73. CHAPTER QUIZ
7. A normally vented solenoid _____ allow fluid to flow to the sump when it is not energized.
Will
will, but at a reduced flow,
will not
Any of these

74. CHAPTER QUIZ
7. A normally vented solenoid _____ allow fluid to flow to the sump when it is not energized.
Will
will, but at a reduced flow,
will not
Any of these

75. CHAPTER QUIZ
8. Student A says that a transmission with electronic shift controls uses a throttle position sensor in place of a throttle valve. Student B says that a vehicle speed sensor is used in place of a governor. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

76. CHAPTER QUIZ
8. Student A says that a transmission with electronic shift controls uses a throttle position sensor in place of a throttle valve. Student B says that a vehicle speed sensor is used in place of a governor. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

77. CHAPTER QUIZ
9. If the solenoids fail in a transmission with electronic shift controls, the transmission will
be ruined if the car is driven.
not have any forward gears.
operate in reverse only.
operate in only one gear.

78. CHAPTER QUIZ
9. If the solenoids fail in a transmission with electronic shift controls, the transmission will
be ruined if the car is driven.
not have any forward gears.
operate in reverse only.
operate in only one gear.

79. CHAPTER QUIZ
10. Student A says that the neutral start switch in a transmission with electronic shift controls is the same as the ones in all other transmissions. Student B says that the neutral start switch in a transmission with electronic shift controls is operated by the manual shift linkage. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

80. CHAPTER QUIZ
10. Student A says that the neutral start switch in a transmission with electronic shift controls is the same as the ones in all other transmissions. Student B says that the neutral start switch in a transmission with electronic shift controls is operated by the manual shift linkage. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

81. CHAPTER QUIZ
11. Student A says that if a transmission uses a comfort power switch, the switch will raise the shift points when it is in the power position. Student B says that if a transmission uses a comfort power switch, it will produce firmer shifts when it is in the comfort position. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

82. CHAPTER QUIZ
11. Student A says that if a transmission uses a comfort power switch, the switch will raise the shift points when it is in the power position. Student B says that if a transmission uses a comfort power switch, it will produce firmer shifts when it is in the comfort position. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

83. CHAPTER QUIZ 12. The TCC should not apply if the Which is correct?
brakes are applied.
engine coolant sensor senses a cold engine.
Which is correct? A B
Both A and B
Neither A nor B

84. CHAPTER QUIZ 12. The TCC should not apply if the Which is correct?
brakes are applied.
engine coolant sensor senses a cold engine.
Which is correct? A B
Both A and B
Neither A nor B

85. CHAPTER QUIZ
13. An electrical circuit must have which of the following to operate?
Power source, conductors, load
Circuit protection, conductor, load
Power source, switch, load
Conductor, load, ground

86. CHAPTER QUIZ
13. An electrical circuit must have which of the following to operate?
Power source, conductors, load
Circuit protection, conductor, load
Power source, switch, load
Conductor, load, ground

87. CHAPTER QUIZ
14. Student A says that diagnostic trouble codes can be read from a light on the dash. Student B says that the diagnostic trouble codes will pinpoint the problem. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

88. CHAPTER QUIZ
14. Student A says that diagnostic trouble codes can be read from a light on the dash. Student B says that the diagnostic trouble codes will pinpoint the problem. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

89. CHAPTER QUIZ 15. The vehicle speed sensor is driven by the
front wheel.
speedometer.
transmission output shaft.
drive shaft.

90. CHAPTER QUIZ 15. The vehicle speed sensor is driven by the
front wheel.
speedometer.
transmission output shaft.
drive shaft.

91. CHAPTER QUIZ 16. The throttle position sensor is located on the
throttle cable.
throttle body.
gas pedal.
transmission case.

92. CHAPTER QUIZ 16. The throttle position sensor is located on the
throttle cable.
throttle body.
gas pedal.
transmission case.

93. CHAPTER QUIZ 17. The throttle position sensor is typically a
thermistor.
rheostat.
potentiometer.
switch.

94. CHAPTER QUIZ 17. The throttle position sensor is typically a
thermistor.
rheostat.
potentiometer.
switch.

95. CHAPTER QUIZ 18. A pulse-width modulated solenoid can be used to
modulate the engine pulses.
smooth the application of the clutches.
signal the computer of a problem.
give the technician information about a problem.

96. CHAPTER QUIZ 18. A pulse-width modulated solenoid can be used to
modulate the engine pulses.
smooth the application of the clutches.
signal the computer of a problem.
give the technician information about a problem.

97. CHAPTER QUIZ 19. If a conductor has infinite resistance it is
corroded.
open.
closed.
grounded.

98. CHAPTER QUIZ 19. If a conductor has infinite resistance it is
corroded.
open.
closed.
grounded.

99. CHAPTER QUIZ
20. A _____ is used to prevent high-voltage spikes from a collapsing electromagnetic field.
Transistor
Relay
Diode
potentiometer

100. CHAPTER QUIZ
20. A _____ is used to prevent high-voltage spikes from a collapsing electromagnetic field.
Transistor
Relay
Diode
potentiometer