Automatic Transmission Shift Lock Control System
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 body control module (BCM) |
| • | The powertrain control module (PCM) |
The body control module (BCM) controls the ground circuit of the shift lock
control solenoid. The following conditions must be met before the BCM will supply
a ground to the shift lock control solenoid:
| • | The ignition is in the ON position. |
| • | The powertrain control module (PCM) sends a class 2 message to
the BCM indicating the transmission is in the PARK position. |
| • | The PCM receives a brake applied input from the brake light switch and
sends a class 2 message to the BCM indicating the brake pedal is depressed. |
With the ignition in the ON position the shift lock control solenoid is supplied
battery voltage from the ign 1 fuse. When BCM supplies a ground
to the control circuit of the automatic transmission shift lock control solenoid,
the solenoid energizes, releasing the mechanical lock. This allows the driver to move
the shift lever out of the PARK position.
Vehicles equipped with VTi variable transmission in cold weather temperatures
below -25°C (-13°F) the PCM will send a class 2 message
to the BCM preventing the operation of the shift lock control solenoid and the temperature
gage light will flash. Once the transmission has warmed above -25°C (-13°F)
the temperature gage light will stop flashing and normal shift lock control operation
will resume.
