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.

P0815 or P0816

P0826

P0815 - Condition 1

The TCM detects an upshift request for 3 seconds or greater in PARK, REVERSE, NEUTRAL, or D6.

P0815 - Condition 2

The TCM detects an upshift for 600 seconds in PARK, REVERSE, NEUTRAL, D2, D4, OR D6.

P0816 - Condition 1

The TCM detects a downshift request for 3 seconds in PARK, REVERSE, NEUTRAL, or D6.

P0816 - Condition 2

The TCM detects a downshift request 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 8 seconds or greater.

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

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, transmission shift lever in L (M), observe the scan tool Driver Shift Request parameter. The reading should display None.
2. Observe the scan tool Driver Shift Request parameter while pressing the tap-up and tap-down switch. The reading should change between Upshift and Downshift.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

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 following circuits for a short to ground:

•	The ignition 1 circuit

•	The Tap Up circuit

•	The Tap Down circuit

⇒	If the fuse is OK, test the following circuits for an open or short to voltage.

•	The ignition 1 circuit

•	The Tap Up circuit

•	The Tap Down circuit

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

⇒	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.