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 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. |
| • | The engine speed is greater than 500 RPM for 5 seconds. |
| • | The time since last gear selector range change is 6 seconds or greater. |
Conditions for Setting the DTC
The TCM detects a downshift request for 1 second or more in PARK and for 10 minutes or more in D4.
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 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 P0816 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 |
Does the Driver Shift Request Status change to Invalid? | -- | Go to Step 4 | Go to Step 5 | ||||||
4 | Replace the Automatic Transmission Shift Program Switch. Refer to Transmission Control Replacement . Did you complete the replacement? | -- | Go to Step 6 | -- | ||||||
5 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 6 | -- | ||||||
6 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 7 | Go to Step 2 | ||||||
7 | 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 |
