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 the downshift circuit active for an extended period of time, then DTC P0816 sets. DTC P0816 is a type C DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0816 Downshift Switch Circuit
Conditions for Running the DTC
| • | No TAP up/ TAP down DTC P0826. |
| • | No IMS DTCs P1815, P1820, P1822, P1823, P1825 or P1826. |
| • | The engine run time is greater than 5 seconds. |
| • | The time since last gear selector range change is greater than 6 seconds. |
Conditions for Setting the DTC
The TCM detects a downshift request for 2 seconds in PARK or for 600 seconds in D4.
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 P0816 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 |
Does the Driver Shift Request Status change to None? | -- | Go to Step 6 | Go to Step 4 | ||||||
4 |
Is the resistance within the specified range? | 8.11-8.39K ohms | Go to Step 6 | Go to Step 5 | ||||||
5 | Test signal circuit for a short to voltage condition. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Step 8 | Go to Step 7 | ||||||
6 | 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 8 | -- | ||||||
7 | 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 8 | -- | ||||||
8 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 9 | Go to Step 2 | ||||||
9 | 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 |
