Page 57 - Hydra-matic 6 Speed RWD Technician's Guide (October 2005)

ELECTRICAL COMPONENTS

COMPONENTS EXTERNAL TO THE TRANSMISSION
Throttle Position (TP) Sensor: The ECM monitors the variable Brake Switch: This parameter displays the state of the brake
voltage signal from the TP sensor to calculate throttle position switch circuit input. This information is transmitted to the TCM
(angle). These input signals are then transmitted over the CAN where it is used as a factor to determine the apply or release state
bus to the TCM, in addition to other vehicle and transmission of the TCC. The scan tool will display Applied when the brake
sensor inputs, in order to determine the appropriate line pressure, pedal is depressed and Released when the brake pedal is released.
shift pattern and TCC apply and release for the transmission. In
general, with greater throttle angle, upshift speeds and line pressure
both increase.
Driver Shift Control (DSC) Switches: These switches are located
either on the steering wheel or on a secondary gate within the
console shift lever mechanism. The TCM uses the switch inputs
Engine Speed Sensor: Monitored by the ECM through the ignition to provide manual shift control to the driver. When a switch is
module, information from this sensor is transmitted over the CAN depressed, the TCM opens a path to ground causing the transmission
bus to the TCM and used to help determine shift patterns and TCC to shift up or down.
apply and release.

Operating Mode Selection Switches: Depending on the customer/
Manifold Absolute Pressure (MAP) Sensor: The MAP sensor application, vehicles may be equipped with switches allowing the
measures changes relative to intake manifold pressure which results driver to select various automatic operating modes (Economy,
from changes in engine load and speed. These changes are Performance, Winter), or manual mode (Driver Shift Control) to
converted to a voltage output which is monitored by the ECM and allow manual shifting by bumping the selector lever up and down.
transmitted over the CAN bus to the TCM in order to adjust line
pressure and shift timing.

Diagnostic Link Connector (DLC): The DLC is a multi-terminal
connector that is located under the vehicle dashboard. The DLC is
Engine Coolant Temperature (ECT) Sensor: The ECM monitors connected by serial data wires to the various control modules
the variable resistance signal from this sensor to determine engine located throughout the vehicle. The DLC can be used to diagnose
coolant temperature. When the engine is cold, resistance is high, conditions in the vehicle's electrical system, TCM or PCM, and
and when the engine is hot, resistance through the sensor is low. various transmission components. Refer to the appropriate Service
The ECM then transmits this information over the CAN bus to the Manual for specific electrical diagnosis information.
TCM where it is used to prevent the TCC from applying when
engine temperature is below approximately 20°C (68°F) (calibratable).

Controller Area Network (CAN) Bus: The CAN bus consists of
two wires that connect the various vehicle control modules together,
Manifold Air Temperature (MAT) Sensor: The ECM monitors allowing them to exchange information about vehicle conditions.
the variable resistance signal from the MAT sensor to determine
manifold air temperature. When the air is cold, resistance is high,
and when the air is hot, resistance through the sensor is low. The
ECM then transmits this information over the CAN bus to the TCM
where it is used as a factor to determine TCC apply. Note: These are typical inputs to the controllers. The
combination and usage of these inputs may vary depending on
model and application.

Accelerator Pedal Position (APP) Sensor: The APP sensor is
monitored by the ECM in order to determine accelerator pedal
position. The ECM uses this signal to open and close the throttle
in response to the driver's commands. It also signals the TCM
when the accelerator pedal is fully depressed, allowing forced
downshifts and maximum performance.

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