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 manual, M, position and is deactivated in all other positions.
If the transmission control module (TCM) detects an invalid voltage on the Up/Down Switch Circuit, DTC P0826 sets. DTC P0826 is a type C DTC.
Conditions for Running the DTC
The engine run time is greater than 5 seconds.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0826 Up and Down Shift Switch Circuit
Conditions for Setting the DTC
The TCM detects an invalid voltage on the TAP Up/Down Signal Circuit for 300 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 records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record. |
| • | The TCM stores DTC P0826 in PCM history. |
Conditions for Clearing the DTC
| • | A scan tool can clear the DTC. |
| • | The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring. |
| • | The PCM 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 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||
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 Intermittent Conditions in Engine Controls - 4.6L | Go to Step 3 | ||||||
3 |
Refer to Circuit Protection - Fuses in Wiring Systems. 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 in Wiring Systems for complete circuit distribution. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Intermittent Conditions in Engine Controls - 4.6L | ||||||
5 | Test the ignition 1 voltage 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 in Wiring Systems. 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 an open, short to voltage or short to ground between the A/T Shift Program Switch and the TCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. 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 Parking System Components Removal in Automatic Transmission 5L40/5L50 - Unit Repair. Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
9 | Replace the TCM. Refer to Control Module References in Computer/Integrating Systems for replacement, set-up 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? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
