Envoy 2WD V8-5.3L (2007)
If the vehicle is equipped with a column mounted gear shift, it has a linear shift assembly on the steering column. The linear shift assembly has a
cable that runs from the linear shift assembly to the ignition lock cylinder case. The purpose of this cable is to prevent the ignition key from being
turned to the OFF position when the transmission is in gear and the vehicle may still be moving. The linear shift assembly cable contains a pin that
is spring loaded to mechanically prevent the ignition key cylinder from being turned to the lock position when the vehicle transmission is not in the
PARK position. If vehicle power is lost, and/or the transmission is not in the PARK position the operator will not be able to turn the ignition key to
the lock position and will not be able to remove the ignition key from the column.
SIR Coil and Module
For additional information on the operation of the SIR coil and module, refer to SIR System Description and Operation.
Automatic Transmission Shift Lock Actuator
The automatic transmission shift lock control system is a safety device that prevents an inadvertent shift out of PARK when the engine is running.
The driver must press the brake pedal before moving the shift lever out of the PARK position. The system consists of the following components: ^
The automatic transmission shift lock control solenoid ^ The automatic transmission shift lock control switch ^ The body control module (BCM) ^
The powertrain control module (PCM)/engine control module (ECM) With the ignition in the ON position, voltage is supplied to automatic
transmission shift lock control switch. Voltage flows through the normally closed contacts of the automatic transmission shift lock control switch
to the automatic transmission shift lock control solenoid. When the BCM receives a class 2 message from the PCM/ECM indicating the
transmission is in the park position the BCM then grounds the automatic transmission shift lock solenoid control circuit. This energizes the
automatic transmission shift lock control solenoid causing the transmission shift lever to be physically locked in the PARK position. When the
brake pedal is pressed the contacts in the automatic transmission shift lock control switch open, de-energizing the automatic transmission shift lock
control solenoid. This allows the shift lever to be move out of the PARK position.
Steering Wheel Angle Sensor or Steering Wheel Position Sensor
The steering wheel position sensor is located somewhere along the steering shaft assembly. The sensor measures the position of the steering wheel
and the speed at which it is rotated. A signal representing this measurement is provided to the vehicle stability enhancement system (VSES)
module. The VSES module uses this signal, along with several others representing different vehicle conditions, to monitor the driving behavior of
the vehicle and ensure that it stays in control. If the VSES module determines that the vehicle is out of control it provides signals to the powertrain
control module (PCM) and the ABS module. These output signals are used to modulate the transmission torque and brake pressure of each of the
vehicles wheels in order to regain control of the vehicle.
