P1877
DTC P1877
Circuit Description
The 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 Low 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 DTC P0705.
* No TAP system DTCs P0815, P0816 or P0826.
* No PSA DTCs P1810, P1816, or P1818.
* No TAP system performance DTC P1876.
* No communication DTC U0100.
* The engine is running for greater than 5 seconds.
Conditions for Setting the DTC
The TCM detects the TAP enable switch is Inactive and the TR switch indicates D3 for 4 seconds 5 times during the same ignition cycle.
Action Taken When the DTC Sets
* The TCM does not request the ECM to 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 speeds while coasting.
* The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
* 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.
* The TCM cancels the DTC default actions when the fault no longer exists and the DTC passes.
