Transmission Control Module (TCM)

The TCM monitors itself by using various software monitoring functions. The TCM is monitored for:

1. If a RAM Read/Write error is detected during initialization, a P0604 fault code will be stored
2. the flash ROM is checked using a checksum calculation. If the checksum is incorrect during a P0605 fault will be stored
3. CPU performance is monitored for incorrect instructions or resets, if detected a P0607 fault code is set
4. If an error is found with NVRAM a P06B8 fault code will be stored

CAN Communications error 

The TCM receives information from the ECM via CAN. If the CAN link fails the TCM no longer has torque or engine speed information available. The TCM will store a U0073 fault code if the CAN Bus is off. The TCM will store a U0100 fault code if it doesn't receive any more CAN messages from the ECM. A U0401 fault codes will be stored if the ECM received invalid/faulted information for the following CAN message items: engine torque, pedal position.

System Voltage: 

the TCM monitors system voltage and stores fault codes if it is out of range low (P0882) or out of range high (P0883). These thresholds are set based on hardware capability.