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 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
The engine speed is greater than 500 RPM for 5 seconds.
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 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 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 | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||
2 |
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. Does the scan tool Driver Shift Request parameter display None? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | ||||||
3 |
Was the fuse open? | -- | Go to Step 4 | Go to Step 5 | ||||||
4 |
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. Did you find and correct the condition? | -- | Go to Step 10 | Go to Testing for Intermittent Conditions and Poor Connections | ||||||
5 | Test the ignition 1 voltage circuit and the TAP Up/TAP Down switch signal circuit of the A/T Shift Program Switch for an open between the fuse block and the A/T Shift Program Switch. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 | ||||||
6 | Test the signal circuit of the A/T Shift Program Switch for a short to voltage between the A/T 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 10 | Go to Step 7 | ||||||
7 |
Is the resistance within the specified range? | 8.11-8.39K ohms | Go to Step 9 | Go to Step 8 | ||||||
8 | Replace the A/T Shift Program Switch. Refer to Transmission Control Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
9 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
10 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 11 | Go to Step 2 | ||||||
11 | 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? | -- | System OK |
