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 transmission control module (TCM) detects TAP enable switch Inactive and the TR switch indicates D3, DTC P1877 sets. DTC P1877 is a type C DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1877 Up and Down Shift Switch Performance - Range Switch in D3
Conditions for Running the DTC
| • | No transmission range switch DTC P0705. |
| • | No TAP system DTCs P0815, P0816 or P0826. |
| • | No PSA DTCs P1810, P1816, or P1818. |
| • | No TAP system performance DTC 1876. |
| • | No communication DTC U0100. |
| • | The engine run time is greater than 5 seconds. |
Conditions for Setting the DTC
The TCM detects the TAP enable switch is Inactive and the TR switch is D3 for 60 seconds.
Action Taken When the DTC Sets
| • | The TCM does not 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 vehicle speeds while coasting. |
| • | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information a Failure Record. |
| • | The TCM stores DTC P1877 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. |
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 TR Sw. parameter display Drive 3? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 |
Does the TR Sw. A/B/C/P display indicate the specified value for D3 range? | Low/Low/Low/Low | Go to Step 13 | Go to Step 4 |
4 |
Did the linkage require adjustment? | -- | Go to Step 21 | Go to Step 5 |
5 |
Does the scan tool TR Sw. A/B/C/P display the specified value? | HI/HI/HI/HI | Go to Step 6 | Go to Step 10 |
6 |
Did you measure ignition voltage at all four terminals? | -- | Go to Step 7 | Go to Step 11 |
7 | Install a fused jumper wire from the TR signal A circuit of the Park/Neutral Position Switch connector to ground while monitoring the scan tool TR Sw. A/B/C/P display. Refer to Circuit Testing and Wiring Repairs . When the TR signal A circuit is grounded, do any other circuits indicate LOW? | -- | Go to Step 12 | Go to Step 8 |
8 | Install a fused jumper wire from the TR signal B circuit of the Park/Neutral Position Switch connector to ground while monitoring the scan tool TR Sw. A/B/C/P display. Refer to Circuit Testing and Wiring Repairs . When the TR signal B circuit is grounded, do any other circuits indicate LOW? | -- | Go to Step 12 | Go to Step 9 |
9 | Install a fused jumper wire from the TR signal C circuit of the Park/Neutral Position Switch connector to ground while monitoring the scan tool TR Sw. A/B/C/P display. Refer to Circuit Testing and Wiring Repairs . When the TR signal C circuit is grounded, do any other circuits indicate LOW? | -- | Go to Step 12 | Go to Step 19 |
10 | Test the TR signal circuits of the TR switch assembly that did not indicate HI for a short to ground between the TCM connector and the Park/Neutral Position Switch connector. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 20 |
11 | Test the TR signal circuits of the Park/Neutral Position Switch Assembly that did not indicate ignition voltage for an open between the TCM connector and the Park/Neutral Position Switch connector. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 20 |
12 | Test the affected signal circuits of the Park/Neutral Position switch assembly for a shorted together condition between the TCM connector and the Park/Neutral Position Switch connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 20 |
13 |
Does the scan tool Driver Shift Request display indicate the change? | Active/Inactive | Go to Step 14 | |
14 |
Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 15 |
15 | Using Test Light check TUTD Enable Signal Ground circuit for an Open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 16 |
16 | Using a DMM check across the Tap Enable switch circuit while moving the gear select lever in and out of the D3 position. Did the Tap Enable Switch open and close as expected on the DMM? | -- | Go to Step 17 | Go to Step 18 |
17 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 21 | -- |
18 | Replace the A/T Shift Program Switch. Refer to Automatic Transmission Shift Lock Control Actuator Replacement . Did you complete the replacement? | -- | Go to Step 21 | -- |
19 | Replace the Park/Neutral Position Switch assembly. Refer to Park/Neutral Position Switch Replacement . Did you complete the replacement? | -- | Go to Step 21 | -- |
20 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 21 | -- |
21 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 22 | Go to Step 2 |
22 | 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 |
