Circuit Description
The transmission adaptive pressure (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 powertrain control module (PCM) 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 PSA DTCs P1810, P1816, or P1818. |
| • | The engine speed is greater than 500 RPM for 5 seconds and not in fuel shut off. |
| • | The time since last gear selector range change is greater than 6 seconds. |
Conditions for Setting the DTC
The PCM detects a downshift request for 2 seconds in park or for 5 minutes in D4.
Action Taken When the DTC Sets
| • | The PCM does not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM commands an alternate coast shift pattern where downshifts occur at higher vehicle speeds while coasting. |
| • | The PCM disables TAP Shift operation. |
| • | The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records. |
| • | The PCM 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 PCM. Does the scan tool Driver Shift Request parameter display None? | -- | Go to Intermittent Conditions in Engine Controls - 3.5L | 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 Floor Shift Control. Refer to Transmission Control Replacement . Did you complete the replacement? | -- | Go to Step 6 | -- | ||||||
5 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems 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? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
