Tap Up and Down Shift Switch Circuit

DTC P0826

Circuit Description

The transmission adaptive pressure (TAP) up/down shift system allows the driver to manually shift gears by using the TAP shift switch located on the automatic transmission shift lever. Pushing the switch forward will command an upshift and pushing the switch rearward will command a downshift. The TAP shift system is activated when the gear selector is in the manual (M) position.

DTC P0826 is a type B DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0826 TAP Up and Down Shift Switch Circuit

Conditions for Running the DTC

* The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
* The engine, input, speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.
* The output speed is greater than 200 RPM.
* Driver shift request is commanded.

Conditions for Setting the DTC

DTC P0826 sets when the transmission control module (TCM) detects an open condition in the TAP up/down shift switch circuit for greater than 6 seconds when driver shift request is commanded.

Action Taken When the DTC Sets

* The TCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
* DTC P0826 is stored in TCM history.
* The TCM disables driver shift request operations.

Conditions for Clearing the MIL/DTC

A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids

* Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
- A bent terminal
- A backed-out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation
* When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
* You may have to drive the vehicle in order to experience a condition.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

3. This step tests signal voltage to the TCM.
4. This step tests supply voltage to the driver shift request switch.
5. This step tests resistance of the driver shift request switch.