Transmission Control Module
DESCRIPTION
The Transmission Control Module (TCM), or Transmission Control Module Assembly (TCMA) is extremely sensitive to Electrostatic Discharge (ESD). Always use a ground strap and follow the ESD guidelines in ELECTROSTATIC DISCHARGE SENSITIVE DEVICES. Failure to follow these instructions may result in damage to the TCM/TCMA.
On 8HP75/850RE equipped vehicles, the transmission valve body includes the TCM, all solenoids and sensors, and can be referred to as the TCMA. The TCM is attached to the valve body between the transmission case and the valve body. If any component of the valve body including the TCM sensors or solenoids need to be replaced, the complete TCMA (valve body) must be replaced.
OPERATION FOR 8HP75/850RE TCM
| 1 - Solenoid A |
| 2- Solenoid D |
| 3 - Solenoid B |
| 4 - Solenoid E |
| 5 - Solenoid C |
| 6 - Torque Converter Control (TCC) Solenoid |
| 7 - Line Pressure Solenoid |
| 8 - Park Release Solenoid |
| 9 - Park Hold Mechanical Solenoid |
| 10 - Park Release Mechanical Valve |
| 1 - Input Speed Sensor (ISS) |
| 2 - TCM (Includes Transmission Temperature Sensor) |
| 3 - External Wire Harness Connector |
| 4 - Output Speed Sensor (OSS) |
| 5 - Park Position Sensor |
The Transmission Control Module (TCM), or Transmission Control Module Assembly (TCMA) is extremely sensitive to Electrostatic Discharge (ESD). Always use a ground strap and follow the ESD guidelines in ELECTROSTATIC DISCHARGE SENSITIVE DEVICES. Failure to follow these instructions may result in damage to the TCM/TCMA.
The valve body, which includes the TCM, controls the delivery and pressure of transmission fluid. The TCM is integral to the valve body. The TCM regulates the amount of hydraulic pressure used to engage the clutches and the TCC, in addition to directing hydraulic pressure to engage or release any given clutch for any given required gear. The TCM will actuate the valves via solenoids based on the position of the shifter, transmission fluid temperature, engine operating conditions, traction conditions and driver demands. During a shift, the TCM will actuate the solenoids to match the gear ranges to the optimal torque range of the engine based on the position of the accelerator pedal, shifter and vehicle speed as determined by the Powertrain Control Module (PCM) based on input from the Vehicle Speed Sensor (VSS) signal from the Antilock Brake System (ABS) module.
If the TCMA is replaced, it must be programmed and a drive learn needs to be performed before returning the vehicle to the customer.