Theory of Operation-P2801 P2803

The Electronic Shift Module (ESM) on column shift vehicles with the NAG1 transmission is part of the Steering Column assembly. The ESM in this configuration contains all the elements used to determine shifter position (PRNDL) and commanded shift states (Auto shift commands, on, off, up and downshift). These states are determined through the TRS Park switch (in the column), internal PRNDL position sensors and Autostick switch (Shift Lever) which is the only component available separately from the ESM. The ESM communicates over the CAN C BUS. These codes are set when implausible differences are detected in the ESM or on the CAN BUS. such as when the ESM detects Park and Wireless Ignition Node (WIN) and or Transmission Control Module (TCM) see the vehicle as not in Park

• When Monitored: 

  Ignition switch in the Run position.Electronic Shift Module (ESM) supply voltage is between 10 and 16 volts.

  • Set Condition: 

    The Transmission Range Switch (TRS) Park switch state does not match the predicted state. * The PRNDL switch state does not match the predicted state. * The Auto stick switch states do not match the predicted state.