Common Electronic Component Description
K71 Transmission Control Module
The Transmission Control Module (TCM) for this transmission is a standalone controller mounted in a bracket to the side cover of the transmission assembly. The TCM has one 66 way connector to interface with vehicle electrical system, transmission assembly and other vehicle control modules. The TCM receives and sends various input and output signals from a number of switches and sensors within the transmission and throughout the vehicle. In addition, the TCM is part of a network of other control modules on the vehicle. This network of control modules will share information with each other, over a common serial data communications line. Based upon the TCM software/calibrations and input information the TCM receives, it will always have final authority of when to allow an upshift or downshift whether in manual mode operation or in drive position for automatic shifting. The TCM will command a 2-3 shift when the accelerator pedal position is below a certain calibrated value. When the pedal position is above this calibrated value, the TCM will command 2-4 shift.
Q77 Transmission Control Solenoid Valve
The 9 speed transmission could contain a maximum of twelve individual solenoids - RPO dependent - installed in various bore locations on the lower control valve body assembly and transmission case. Eight of the twelve solenoid valves are used to control pressure regulation and direction of transmission fluid. The four ON/OFF solenoid valves are only used to direct transmission fluid.
The normal operating current range for these solenoid valves is between 0 - 1.2 amps. If the TCM detects an electrical circuit malfunction or excessive current flow, the TCM will turn OFF the high side driver to that solenoid and set a DTC. The high side driver will reset when the circuit fault is corrected and the ignition switch is cycled.
There are two slightly different designed variations of the pressure regulating solenoid valves used on this transmission. They are; linear variable force solenoid and normally low variable force solenoid.
Normally Low - Linear Solenoids
- A normally low linear solenoid actuator is an electro-mechanical device that converts electrical power into a mechanic pushing or pulling force or motion.
- When energized, the solenoid armature applies force to the face of a pressure regulating spool valve.
- The solenoid actuator applies minimum force with minimum current applied to the solenoid coil.
- The solenoid actuator applies maximum force with maximum current applied to the solenoid coil.
- Transmission control solenoid valves 1, 2, 5 and 6 are normally low.
Normally Low - Variable Force Solenoid
A normally low variable force solenoid is an electro-mechanically operated valve. The valve is controlled by an electric current through the solenoid coil.
- The solenoid valve varies the control pressure depending on the current applied to the solenoid coil.
- The solenoid valve control pressure is low with no or minimum current applied to the solenoid coil.
- The solenoid valve control pressure increases with increasing current applied to the solenoid coil.
- Nominal resistance of a variable force solenoid is 5.1 Ohms +/-.3 Ohms @ 20°C (68°F). As the temperature of the solenoid windings increase, the resistance will also increase. When the solenoid temperature is at 100°C (212°F), the resistance value will be approximately 6.7 Ohms +/-.4 Ohms.
- Transmission control solenoid valves 3, 4, and 8 are of the normally low design.
Normally High - Variable Force Solenoid
- A normally high variable force solenoid is an electro-mechanically operated valve. The valve is controlled by an electric current through the solenoid coil.
- The solenoid valve varies the control pressure depending on the current applied to the solenoid coil.
- The solenoid valve control pressure is high with no or minimum current applied to the solenoid coil.
- The solenoid valve control pressure decreases with increasing current applied to solenoid coil.
- Nominal resistance of a variable force solenoid is 5.1 Ohms +/-.3 Ohms @ 20°C (68°F). As the temperature of the solenoid windings increase, the resistance will also increase. When the solenoid temperature is at 100°C (212°F), the resistance value will be approximately 6.7 Ohms +/-.4 Ohms.
- Transmission control solenoid valve 7 is a normally high solenoid.
ON/OFF Solenoids
- The ON/OFF solenoid valve is an electro-mechanically operated valve. The valve is controlled by an electric current through the solenoid coil.
- This solenoid is normally closed solenoid that is controlled ON (fully open) or OFF (fully closed).
- Nominal resistance of an On/Off solenoid is 12.0 Ohms +/-.3 Ohms @ 20°C (68°F). As the temperature of the solenoid windings increase, the resistance will also increase. When the solenoid temperature is at 100°C (212°F), the resistance value will be approximately 15.8 Ohms +/-.4 Ohms.
- Transmission control solenoid valves 9, 10, 11 & 12 are ON/OFF solenoids.
Solenoid Characterization
Transmission control solenoid valves 1 - 8 are pressure regulating valves. Each solenoid valve is tested after assembly to determine the output fluid pressure at certain electrical values, applied to the coil winding. This information is referred to as solenoid current/pressure data points. The solenoid valves are tested two ways, with an increasing and then a decreasing electrical current applied to the coil winding. The resultant current versus pressure data points are saved and assigned a file number. This file number is marked on the solenoid valve housing end or on the valve body itself. The solenoid performance data file is stored on the TIS web site. This data file is programmed and stored in the vehicle's TCM. Replacing any of the following components will require the TCM to be programmed with either the new or existing solenoid valve performance data, depending on what component is replaced.
- Transmission assembly - program the TCM with the new data file stored on the TIS web site for all pressure regulating solenoid valves.
- Lower control valve body assembly with solenoid valves - program the TCM with the new data file stored on the TIS web site for all pressure regulating solenoid valves.
- Transmission Control Module - program the TCM with the existing data file stored on the TIS web site for all pressure regulating solenoid valves.
- One or more solenoids - program the TCM with the new data file stored on the TIS web site for all pressure regulating solenoid valves that were replaced.
B13 Transmission Fluid Temperature Sensor
The transmission fluid temperature sensor is a 2 wire negative temperature coefficient thermistor. The TCM supplies a 5 V signal circuit and a low reference circuit to the transmission fluid temperature sensor. The transmission fluid temperature sensor measures the temperature of the fluid in the transmission fluid pan. As the temperature of the fluid increase, the resistance of the sensor decreases, varying the voltage on the signal circuit. The transmission fluid sensor is part of the transmission internal wire harness assembly and has no serviceable parts. If the transmission fluid temperature sensor is faulty, then replace the internal transmission wire harness that has the sensor attached to it.
B14E Transmission Input/Intermediate Shaft Speed Sensor
The input and intermediate speed sensors are housed together in one component assembly. The sensor is mounted on the exterior of the transmission case. Each sensor is triggered by a separate reluctor ring inside the transmission case. The input and intermediate speed sensors are both hall-effect type sensors. The TCM supplies a single 9 V reference circuit to power up both sensors. Each sensor has an independent signal circuit that returns to the TCM. The TCM uses the signals to determine the rotational speed of the input shaft and the reaction gear set. As the rotational speed of the reluctor wheel increases, the frequency of the speed signal increases. The transmission control module uses this information along with the output speed sensor signal to determine transmission line pressure, shift patterns, correct gear ratio and torque converter clutch slip speed.
- The input reluctor ring is part of the 5-7-R and 6-7-9 clutch subassembly.
- The intermediate reluctor ring is part of the 3-8 and 5-7-R clutch hub assembly.
B14A Transmission Output Shaft Speed Sensor
The output speed sensor assembly is a two wire hall-effect type sensor. The sensor is mounted on the interior of the transmission case. The TCM supplies a 9 V reference circuit and signal circuit to the output speed sensor. As the rotational speed of the output carrier assembly increases, the frequency of the output speed sensor signal increases. The reluctor ring is part of the Park gear assembly, which is splined to the transmission output shaft. The TCM used the output speed sensor signal along with the input and intermediate speed sensor signals to determine transmission line pressure, shift patterns, correct gear ratio and the torque converter clutch slip speed.
Automatic Transmission Wiring Harness
The transmission internal wire harness is serviced by replacement only. No repairs to the internal wire harness should be attempted.
B280 Automatic Transmission Accumulator Solenoid Valve - If Equipped
The Transmission Fluid Pressure Accumulator Solenoid Valve is part of the Stop/Start system on the vehicle. The automatic transmission auxiliary fluid accumulator is used to supply transmission fluid line pressure to the appropriate clutches for an auto start event. Attached to the accumulator is a normally closed ON/OFF solenoid. When the ignition is ON, the engine control ignition relay supplies 12 V to the accumulator solenoid. To complete the circuit, the transmission control module (TCM) supplies a control circuit to the accumulator solenoid. When the engine control module (ECM) requests an auto start event, a serial data message is sent to the TCM, to command the solenoid ON. This allows captured pressurized fluid to exit the accumulator to apply the clutches for a 1st gear start.