Content .. 1171 1172 1173 1174 ..
Chevrolet Silverado / GMC Sierra. Manual - part 1173
ELECTRONIC COMPONENT DESCRIPTION (TCM)
Automatic Transmission Input Speed Sensor Assembly
Fig. 537: View Of A/T Input Speed Sensor Assembly
Courtesy of GENERAL MOTORS CORP.
The Automatic Transmission Input Speed Sensor (AT ISS) Assembly is a hall-effect sensor that
produces an input speed signal as the turbine shaft rotor teeth pass in front of the sensor tip.
The AT ISS is made of a permanent magnet with an iron pole piece and an integrated circuit (IC)
chip with a two-element transducer molded into a plastic housing. The two-element transducer
functions as an on/off switch by sensing changes in the magnetic field strength. The dual element
design greatly increases the sensor's switching accuracy.
Because the turbine shaft is splined to the torque converter, it spins at engine speed. As the
turbine shaft spins, the rotor teeth pass in front of the sensor tip, changing the magnetic field. As a
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
result, the transducers are sensing high and low magnetic signals. The IC chip will then amplify
and filter the high and low signal. Therefore, whenever the engine is running, the sensor will
produce high and low signals proportional to turbine shaft speed. The more rotor teeth passing by
the sensor's magnetic field in a specific amount of time, the faster the turbine shaft is spinning.
The ISS assembly is attached to the pump cover with the tip of the sensor passing though the
stator shaft and sleeve. The ISS mounting bolt passes through a steel insert and into a threaded
hole in the pump cover. The ISS wiring harness is routed and secured to the pump cover with
clip-on brackets. At the transmission control module (TCM), the signal is electronically
converted and is interpreted as transmission input speed. The TCM uses transmission input speed
together with the transmission output speed to provide shift energy and torque management
capabilities, improved shift quality (feel), increased TCC function, gear ratios that are more
accurate and enhanced transmission diagnostics.
Electronic Component Description (TCM)
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
Fig. 538: Transmission Control Module (TCM)
Courtesy of GENERAL MOTORS CORP.
The transmission control module (TCM) (5.3L only) is mounted near the lower left front of the
engine and connects directly to the engine wiring harness. A single 49-way connector is used to
make the connection between the vehicle wiring and the TCM. The TCM is an electronic control
module that receives input or provides output in order to control the operation of the 4L60
automatic transmission.
The TCM receives the following inputs from the engine control module (ECM):
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
Engine speed and torque values
Engine intake air temperature (IAT), accelerator pedal position (APP) information
Engine coolant temperature (ECT)
Kick-down request
Traction control status
Driver selected shift mode
Air-conditioning (A/C) status
Cruise control status
The ECM provides this data to the TCM through the controller area network (CAN). The CAN is
a 2-wire communication connection between the 2 controllers.
Other TCM inputs are the following:
Battery and ignition voltage
Brake switch status
Transmission manual shift shaft switch assembly
Transmission fluid temperature (TFT)
Transmission vehicle speed sensor (VSS)
The TCM provides the following outputs in order to control the automatic transmission:
Shift solenoids to control transmission shifting
TCC PWM solenoid operation controls the apply and release of the torque converter clutch
ASM
Pressure control solenoid (PCS) regulates transmission line pressure
Other TCM outputs provided to the ECM are the following:
MIL illumination request
Vehicle speed
Transmission input speed
Transmission fluid temperature
Commanded gear status
TCC status
Torque reduction requests
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
Content .. 1171 1172 1173 1174 ..