For 1990-2009 cars

### Circuit Description

The TAP Shift system allows the driver to manually shift gears by using the TAP Shift switches located on the automatic transmission shift lever. Pushing the shifter handle forward will command an upshift and pulling the shifter handle back 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.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Select The DTC Info parameter on the scan tool.

Are DTC's P0815, P0816, P0826 or P1876 set?

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Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 2

2 |

1. Select the Driver Shift Control parameter on the scan tool.
2. Ensure that the automatic transmission (AT) shift lever is in the PARK position.

Does the scan tool Driver Shift Control parameter display Inactive?

--

Go to Step 3

Go to Step 8

3 |

1. Select the Manual Shift (M) position on the AT shift lever.
2. Observe the Driver Shift Control parameter on the scan tool.

Does the scan tool Driver Shift Control parameter display Active?

--

Go to Step 6

Go to Step 4

4 | Using the J 39200 DMM and the J 35616 GM terminal test kit, measure the voltage between the TAP Up/TAP Down enable signal circuit and a known good ground at the AT shift lever connector. Does the voltage measure near the specified voltage? | 12 V | Go to Step 5 | Go to Step 9
5 | Using the J 39200 DMM and the J 35616 GM terminal test kit, measure the voltage between the TAP Up/TAP Down enable signal circuit and the TAP Up/TAP Down ground circuit at the AT shift lever connector. Does the voltage measure near the specified voltage? | 12 V | Go to Step 11 | Go to Step 10
6 |

1. Select the Driver Shift Request parameter on the scan tool.
2. While observing the scan tool, move the AT shift lever in the upshift position.

Does the Driver Shift Request parameter display upshift?

--

Go to Step 7

Go to Step 11

7 | While observing the scan tool, move the AT shift lever in the downshift position. Does the Driver Shift Request parameter display downshift? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 11
8 | Test the Driver Shift Control enable signal circuit for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12
9 | Test the Driver Shift Control enable signal circuit for an open. Refer to Testing for Continuity and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12
10 | Test the Driver Shift Control ground circuit for an open. Refer to Testing for Continuity and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 13 | --
11 | Replace the floor shift control. Refer to Transmission Control Replacement. Did you complete the replacement? | -- | Go to Step 13 | --
12 | Replace the instrument panel cluster (IPC). Refer to Instrument Cluster Replacement. Did you complete the replacement? | -- | Go to Step 13 | --
13 | Perform the following procedure in order to verify the repair:

1. Select the Driver Shift Control parameter on the scan tool.
2. With the AT shift lever in PARK (P) the scan tool should indicate Inactive.
3. With the AT shift lever in Manual (M) the scan tool should indicate Active.
4. Select the Driver Shift Request parameter on the scan tool.
5. With the AT shift lever in Manual (M) the scan tool should indicate None.
6. With the AT shift lever in upshift (+) position the scan tool should indicate Upshift.
7. With the AT shift lever in downshift (-) position the scan tool should indicate downshift.

Do the Driver Shift Control and the Driver Shift Request parameters indicate the proper display?

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System OK

Go to Step 1