Diagnostic Aids
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
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