GM Service Manual Online
For 1990-2009 cars only

Object Number: 1595261  Size: MF
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Control Module References

Circuit Description

The touch activated power (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 commands an upshift and pushing the Down switch commands 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 an invalid voltage on the TAP up/TAP down switch signal circuit, then DTC P0826 sets. DTC P0826 is a type C DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0826 Up and Down Shift Switch Circuit

Conditions for Running the DTC

    • TAP up/TAP down DTC P0826 is not active.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • The time since the last gear selector range change is 6 seconds or greater.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

    • The TCM does not illuminate the malfunction indicator lamp (MIL).
    • The TCM commands an alternate coast shift pattern where downshifts occur at higher vehicle speeds while coasting.
    • The TCM disables the TAP shift operation.
    • 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 P0826 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.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Important: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear DTC Information function erases the Failure Records from the TCM.

  4. Record the DTC Failure Records.
  5. Clear the DTC.
  6. Select Driver Shift Request Status on the scan tool.

Does the scan tool Driver Shift Request parameter display None?

--

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Select Driver Shift Request Voltage on the scan tool.

Does the Driver Shift Request Voltage parameter display a value higher than specified?

0.5 V

Go to Step 4

Go to Step 5

4

Does the Driver Shift Request Voltage parameter display a value lower than specified?

4.5 V

Go to Step 9

Go to Step 8

5

  1. Inspect the fuse in the ignition 1 voltage circuit for an open. Refer to Circuit Protection - Fuses .
  2. Replace the fuse, if necessary.

Is the fuse open?

--

Go to Step 6

Go to Step 7

6

    Important: The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Power Distribution Schematics for complete circuit distribution.

  1. Test the ignition 1 voltage circuit of the automatic transmission shift program switch for a short to ground between the fuse block and the automatic transmission shift program switch.
  2. Test the TAP up/TAP down switch signal circuit for a short to ground between the automatic transmission shift program switch and the TCM.

Refer to Testing for Short to Ground and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Testing for Intermittent Conditions and Poor Connections

7

Test the ignition 1 voltage circuit and the TAP Up/TAP Down switch signal circuit of the automatic transmission shift program switch for an open between the fuse block and the automatic transmission shift program switch. Refer to Testing for Continuity and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 8

8

Test the signal circuit of the automatic transmission shift program switch for a short to voltage between the automatic transmission shift program switch and the TCM. Refer to Testing for a Short to Voltage and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

9

  1. Using the J 35616 GM-approved terminal test kit, connect a DMM between the ignition 1 voltage and the TAP up/TAP down switch signal circuits of the automatic transmission shift program switch.
  2. Measure the resistance of the automatic transmission shift program switch.

Is the resistance within the specified range?

8.11-8.39K ohms

Go to Step 11

Go to Step 10

10

Replace the automatic transmission shift program switch. Refer to Transmission Control Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the TCM. Refer to Control Module References for replacement, set-up, and programming.

Did you complete the replacement?

--

Go to Step 12

--

12

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear DTC Information.
  3. Operate the vehicle under the following conditions:
  4. • Start the engine.
    • Observe Driver Shift Request on the scan tool.
    • Ensure the Driver Shift Request is not invalid for 4 seconds or greater.
  5. Select Specific DTC.
  6. Enter DTC P0826.

Has the test run and passed?

--

Go to Step 13

Go to Step 2

13

With a scan tool, observe the stored information, capture info and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK