GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 G6 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 DTC P1877

Object Number: 1379697 Size: MF
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Control Module References

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 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 TAP system DTCs P0815, P0816 or P0826.
    • No PSA DTCs P1810, P1816, or P1818.
    • No TAP system performance DTC 1876.
    • The engine run time is greater than 5 seconds.

Conditions for Setting the DTC

The PCM detects the TAP enable switch is Inactive and the TR switch is D3 for 3 seconds five times during the same trip.

Action Taken When the DTC Sets
    • The PCM does not illuminate the malfunction indicator lamp (MIL).
    • The PCM disables TAP Shift operation.
    • The PCM commands an alternate coast shift pattern where downshifts occur at higher vehicle speeds while coasting.
    • The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information a Failure Record.
    • The PCM stores DTC P1877 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.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.

    3. 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.

  3. Record the DTC Failure Records.
  4. Clear the DTC.
  5. Select Driver Shift Request Status on the scan tool.

Does the scan tool Driver Shift Request parameter display None?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 3

3

Select Driver Shift Request Voltage on the scan tool.

Does the Driver Shift Request Voltage parameter display a value higher than specified?

0.5 V

Go to Step 4

Go to Step 5

4

Does the Driver Shift Request Voltage parameter display a value lower than specified?

4.5 V

Go to Step 9

Go to Step 8

5
  1. Inspect the fuse in the ignition 1 voltage circuit for an open.

    2. Refer to Circuit Protection - Fuses in Wiring Systems.

  2. Replace the fuse if necessary.

Was the fuse open?

--

Go to Step 6

Go to Step 7

6

    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.

  1. Test the ignition 1 voltage circuit of the Floor Shift Control for a short to ground between the fuse block and the Floor Shift Control.
  2. Test the signal circuit for a short to ground between the Floor Shift Control and the PCM.

Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Intermittent Conditions in Engine Controls - 3.5L

7

Test the ignition 1 voltage circuit of the Floor Shift Control for an open between the fuse block and the Floor Shift Control.

Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 8

8

Test the signal circuit of the Floor Shift Control for an open or short to ground between the Floor Shift Control and the PCM.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

9
  1. Using the J 35616 GM terminal test kit, connect a DMM between the ignition 1 voltage circuit and the TAP up/TAP down signal circuit of the Floor Shift Control.
  2. Measure the resistance of the Floor Shift Control.

Is the resistance within the specified range?

8.11-8.39K ohms

Go to Step 11

Go to Step 10

10

Replace the Floor Shift Control.

Refer to Transmission Control Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

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 12

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12

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear DTC Information.
  3. Operate the vehicle under the following conditions:
    4. • Start the engine.
    • Observe Driver Shift Request on the scan tool.
    • Ensure the Driver Shift Request is not Inactive when in D3 for at least 5 seconds.
  4. Select Specific DTC.
  5. Enter DTC P1877.

Has the test run and passed?

--

Go to Step 13

Go to Step 2

13

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