P1877
DTC P1877
TAP Shift Circuit Performance:
Circuit Description
The transmission adaptive pressure (TAP) Shift system allows the driver to manually shift gears by using the TAP Shift switches located on the Automatic Transmission Shifter. Pushing the Up switch will command an upshift and pushing the Down switch will command a downshift. The TAP Shift system is activated when the gear selector is in the D3 position and is deactivated in all other positions.
If the transmission control module (TCM) detects TAP enable switch Inactive and the TR switch indicates D3, DTC P1877 sets. DTC P1877 is a type C DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1877 Up and Down Shift Switch Performance - Range Switch in D3
Conditions for Running the DTC
^ No transmission range switch DTC P0705.
^ No TAP system DTCs P0815, P0816 or P0826.
^ No PSA DTCs P1810, P1816, or P1818.
^ No TAP system performance DTC 1876.
^ No communication DTC U0100.
^ The engine run time is greater than 5 seconds.
Conditions for Setting the DTC
The TCM detects the TAP enable switch is Inactive and the TR switch is D3 for 60 seconds.
Action Taken When the DTC Sets
^ The TCM does not illuminate the malfunction indicator lamp (MIL).
^ The TCM disables TAP Shift operation.
^ The TCM commands an alternate coast shift pattern where downshifts occur at higher vehicle speeds while coasting.
^ The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information a Failure Record.
^ The TCM stores DTC P1877 in TCM history.
Conditions for Clearing the DTC
^ A scan tool can clear the DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non emission related diagnostic fault occurring.
