Controller Modes of Operation

CONTROLLER MODES OF OPERATION

Permanent limp-in mode
When the TCM determines there is a nonrecoverable condition present that will not allow proper transmission operation, it will place the transmission in permanent limp-in mode. When the condition occurs the TCM will turn off all solenoids as well as the solenoid supply output circuit. If this occurs while the vehicle is moving, the transmission will remain in the current gear until the ignition is turned off or shifter is placed in the "P" position. Once the shifter has been placed in "P" the Transmission will only allow 2nd gear operation. If the problem occurs while the vehicle is not moving the transmission will only allow 2nd gear operation.

Temporary limp-in mode
This mode is the same as the permanent limp-in mode except if the condition is no longer present the system will resume normal operation. (Recoverable DTC)

Undervoltage limp-in mode
When the TCM detects that system voltage has dropped below 8.5 volts it will disable voltage dependent diagnostics and place the transmission in the temporary limp-in mode. When the TCM senses that the voltage has risen above 9.0 volts, normal transmission operation will be resumed.

Hardware Error Mode
When the TCM detects a major internal error the transmission will be placed in the permanent limp-in mode and cease all communication over the CAN bus. Once the TCM has entered this mode normal transmission operation will not resume until all DTCs are cleared from the TCM.

Loss of Drive
If the TCM detects a situation that has resulted or may result in engine or transmission failure, the transmission will be placed in the neutral position. Improper Ratio, Input Sensor Overspeed, or Engine Overspeed DTCs will cause the loss of drive.

Controlled Limp-in Mode
When a failure condition does not require the TCM to shut down the solenoid supply, but the failure is of a degree where the TCM will place the transmission into a predefined gear, there will be several shift performance issues. Examples of this are, with the transmission slipping the controller will attempt to place the transmission into third gear and maintain third gear for all forward drive conditions. Another example is some of the CAN bus message issues if the TCM does not receive required information from the Engine Controller, then default values are used which may result in poor transmission shift performance.