Chevrolet Silverado / GMC Sierra. Service manual — part 1175

The torque converter clutch (TCC) solenoid valve is a normally-open exhaust valve that is used to
control torque converter clutch apply and release. When grounded (energized) by the
transmission control module (TCM), the TCC solenoid valve stops converter signal oil from
exhausting. This causes converter signal oil pressure to increase and move the TCC solenoid valve
into the apply position.

Torque Converter Clutch Pulse Width Modulation Solenoid Valve

Fig. 543: View Of Torque Converter Clutch Pulse Width Modulation Solenoid Valve
Courtesy of GENERAL MOTORS CORP.

The torque converter clutch pulse width modulation solenoid valve controls the fluid acting on
the converter clutch valve. The converter clutch valve controls the torque converter clutch (TCC)
apply and release. This solenoid is attached to the control valve body assembly within the
transmission. The TCC PWM solenoid valve provides a smooth engagement of the torque
converter clutch by operating during a duty cycle percent of ON time.

Transmission Fluid Pressure (TFP) Manual Valve Position Switch

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis

Silverado, Sierra & Silverado

Fig. 544: View Of Transmission Fluid Pressure (TFP) Manual Valve Position Switch
Courtesy of GENERAL MOTORS CORP.

The TFP manual valve position switch consists of 5 pressure switches (2 normally-closed and 3
normally-open) on the control valve body that sense whether fluid pressure is present in 5
different valve body passages. The combination of switches that are open and closed is used by
the transmission control module (TCM) in order to determine the actual manual valve position.
The TFP manual valve position switch, however, cannot distinguish between PARK and
NEUTRAL because the monitored valve body pressures are identical in both cases.

The switches are wired to provide three signal lines that are monitored by the TCM. These signals
are used to help control line pressure, torque converter clutch apply and shift solenoid valve
operation. Voltage at each of the signal lines is either 0 or 12 volts.

In order to monitor the TFP manual valve position switch operation, the TCM compares the
actual voltage combination of the switches to a TFP combination table stored in its memory.

The TFP manual valve position switch signal voltage can be measured from each pin-to-ground
and compared to the combination table. On the automatic transmission (AT) wiring harness

IMPORTANT: Seven valid combinations and 2 invalid combinations are

available from the transmission fluid pressure (TFP) manual
valve position switch. Refer to the Transmission Fluid Pressure
Manual Valve Position Switch Logic table for valid/invalid
combinations for range signal circuits A, B and C.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis

Silverado, Sierra & Silverado

assembly, pin N is signal A, pin R is signal B, and pin P is signal C. With the AT wiring harness
assembly connected and the engine running, a voltage measurement of these 3 lines will indicate a
high reading (near 12 volts) when a circuit is open, and a low reading (zero volts) when the
circuit is switched to ground.

The transmission fluid temperature (TFT) sensor is part of the TFP manual valve position switch
assembly.

Vehicle Speed Sensor Assembly

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis

Silverado, Sierra & Silverado

Fig. 545: Vehicle Speed Sensor Assembly
Courtesy of GENERAL MOTORS CORP.

The vehicle speed sensor (VSS) assembly provides vehicle speed information to the transmission
control module (TCM). The VSS assembly is a permanent magnet (PM) generator. The PM
generator produces a pulsing AC voltage as rotor teeth on the transmission output shaft pass

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis

Silverado, Sierra & Silverado