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. Ignition voltage flows from the ignition 1 fuse through the TAP switch resistor array to the transmission control module (TCM). The TAP shift system is activated when the gear selector is in the manual (M) position. In the M range position, the TAP enable switch is closed and this activates the system by completing the TAP enable signal circuit from the body control module (BCM) to ground. TAP system is deactivated in all other range positions.

The engine speed is between 500-6,500 RPM for at least 5 seconds.

P0815 or P0816

P0815

The TCM detects an upshift request for 3 seconds in PARK, REVERSE, NEUTRAL, or D6- and for 600 seconds in PARK, REVERSE, NEUTRAL, D2, D4, OR D6.

P0816

The TCM detects a downshift request for 3 seconds in PARK, REVERSE, NEUTRAL, or D6- and for 600 seconds in PARK, REVERSE, NEUTRAL, D2, D4, or D6.

P0826

The TCM detects an invalid voltage on the TAP up/down signal circuit for 5 seconds.

DTCs P0815, P0816, and P0826 are Type C DTCs.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

DTC Type Reference

Electrical Information Reference

With the engine ON, engage the Tap Up and Tap Down switch positions while observing the Driver Shift Request scan tool parameter. The parameter should change to reflect the selected Up or Downshift switch position and with no Up or Downshift switch position selected the parameter should display None.

P0815

1. Select the Driver Shift Request parameter.
2. Disconnect the automatic transmission (AT) TAP shift switch connector.

⇒	If the parameter status changes from Upshift to Invalid, replace the AT TAP shift switch.

⇒	If the parameter status does not change, replace the control solenoid (w/body and TCM) valve assembly.

P0816

1. Select the Driver Shift Request parameter.
2. Disconnect the AT TAP shift switch connector.

⇒	If the parameter status changes from Downshift to Invalid, replace the AT TAP shift switch.

⇒	If the parameter status does not change, replace the control solenoid (w/body and TCM) valve assembly.

P0826

1. Inspect the fuse in the ignition 1 voltage circuit for an open.

⇒	If the fuse is open, test the ignition 1 and the tap up and tap down circuit for a short to ground.

⇒	If the fuse is OK, test the ignition 1 and the tap up and tap down signal circuit for an open or short to voltage.

2. Test the AT TAP shift switch for correct resistance value, 8.11-8.39 ohm.

⇒	If the resistance is not within specifications, replace the switch assembly.

⇒	If the resistance is within specifications, replace the control solenoid (w/body and TCM) valve assembly.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.