Modules that are connected to the CAN serial data circuits monitor each other for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. the modules have prerecorded information about messages that are exchanged on the serial data circuits. The supervised and periodic messages are used by the receiving module as an availability, and state of health indicator from the transmitting module. If the engine control module (ECM) detects a message that indicates a loss of communication, invalid or corrupted serial data, or an active malfunction in the transmission control module (TCM), that requires ECM intervention, DTC P0701 sets.

This diagnostic procedure supports the following DTC:

DTC P0701 Transmission Control System Performance

A module which loses power during the current ignition cycle, will have a Loss of Communication DTC set by the other modules that require information from the failed module.

If the TCM, using a faulty manifold absolute pressure (MAP) signal, calculates an invalid torque value, the TCM will command ECM intervention and set a DTC P0701.

If there is an active vehicle speed malfunction in the TCM, DTC P0701 will set.

If the ECM's ignition 1 voltage circuit, that is used to wake up the module is open, the TCM may set a DTC U2105 and request a limp-home mode, which will result in DTC P0701 also being set.