Electrical diagram of the automatic transmission control unit (automatic transmission)
Designations:
*ECM: Engine Control Module
*TCM: Transmission Control Module
* VSS: Vehicle Speed Sensor
* TPS: Throttle Position Sensor
* ICP: Manifold Pressure Sensor
* MAP: Manifold Absolute Pressure Sensor
*ECT: Engine Coolant Temperature Sensor
* A/T: automatic transmission
* Sol: Solenoid
*P: Parking
*R: Reverse
*N: Neutral
*D: Drive
*1: First gear
*2: Second gear
Basic scheme:
“`
ECM — VSS — TCM — TPS — ICP — MAP — ECT — A/T
|
|— Sol (P) — Sol (R) — Sol (N) — Sol (D) — Sol (1) — Sol (2)
“`
Control signals:
* The ECM sends speed, throttle position, manifold pressure, and engine coolant temperature signals to the TCM.
* The TCM uses these signals to determine the appropriate gear for the current driving conditions.
* The TCM provides signals to the solenoids to engage or disengage the clutches, which apply torque to the various planetary gears in the automatic transmission.
Feedback signals:
* The TCM sends the selected gear signal back to the ECM.
* The ECM uses this signal to adjust engine idle speed and prevent the transmission from shifting too low at high engine speeds.
Additional components:
*Diagnostic Connector: Used to connect a diagnostic scanner to read trouble codes and real-time data.
* Fuse and Relay Box Relay: Provides power to the automatic transmission control unit and solenoids.
* Instrument Cluster: Displays gear position and warning signals (eg “Check Transmission”).
Note: The electrical diagram may vary depending on the design of the automatic transmission and the vehicle model.