Chevrolet Trax: DTC P1876

Up and Down Shift Enable Switch Circuit Low Voltage

Circuit/System Description

When the shift lever is placed in manual mode (M), the driver shift request , also known as the tap shift function, is activated. The driver shift request allows the vehicle operator to shift gears by pushing the plus (+) button for an upshift or minus (-) button for a downshift. The body control module (BCM) supplies a signal circuit to the shift controller. The shift controller has switches connected to a resistor array. When the lever is in the M position, a voltage drop occurs across the resistor network. When the plus or minus button is pushed, a corresponding voltage drop occurs across the resistor network. This voltage drop is monitored by the BCM. The BCM will send the request to the transmission control module (TCM) to perform the upshift or downshift. The TCM will not allow shifting to the next higher gear if the vehicle speed or engine RPM is too low. The transmission will not allow shifting to the next lower gear if the vehicle speed or engine RPM is too high.

Conditions for Running the DTC

• DTC P0815, P0816, P0826, P1761, P1825, P1876, P1877, P1915, or U0100 is not set.
• Engine speed is 400-7,500 RPM for 5 s.
• Ignition voltage is 9-32 V.
• Runs continuously when above conditions are met.

Conditions for Setting the DTC

Transmission control module (TCM) detects a Tap Enable Switch request for 3 s when the shift lever is in Park, Reverse, or Neutral, a total of 5 times.

Action Taken When the DTC Sets

• P1876 is a Type C DTC.
• TCM inhibits Tap-Up/Tap-Down functions.
• TCM inhibits manual up, manual down shifts with the shift selector.

Conditions for Clearing the DTC

P1876 is a Type C DTC

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics (Encore, MH8 or MHB) , Automatic Transmission Controls Schematics (Trax, MH8 or MHB)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

• Inline Harness Connector End Views (Encore) , Inline Harness Connector End Views (Trax)

Description and Operation

• Electronic Component Description
• Transmission Component and System Description
• Transmission General Description

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (LUV) , Powertrain Diagnostic Trouble Code (DTC) Type Definitions (2H0)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

WARNING: Refer to Parking Brake and Drive Wheels Warning .

1. Verify DTC P182E or P1915 was not set by reviewing the scan tool Freeze Frame/Failure Records.

If DTC P182E or P1915 was set

Refer to DTC P182E or P1915.

If DTC P182E or P1915 was not set

2. Ignition ON.

NOTE: The engine may have to be started to move the shift lever out of the Park position. Once out of the Park position, the engine can be turned OFF.

3. Verify the gear shift lever position matches the scan tool TCM Internal Mode Switch parameter while slowly moving the gear shift lever from Park through all ranges.

If the specified values are not correct

Refer to Range Selector Lever Cable Adjustment .

If the specified values are correct

4. Shift lever in the M position.
5. Verify the scan tool Driver Shift Request parameter changes from Inactive to Upshift when the plus button is pressed, and from Inactive to Downshift when the minus button is pressed.

If the Driver Shift Request parameter does not display the correct values

Refer to Circuit/System Testing

If the Driver Shift Request parameter displays the correct values

6. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
7. Verify the DTC does not set.

If the DTC sets

Refer to Circuit/System Testing.

If the DTC does not set

8. All OK.

NOTE: You must perform Circuit/System Verification first.

1. Ignition OFF, disconnect the harness connector at the S3 Transmission Shift Lever.
2. Test for less than 10 ohms between the vehicle harness connector terminal 2 and ground.

If 10 ohms or greater

1. Ignition OFF, disconnect the vehicle harness at the ground connection.
2. Test for less than 2 ohms in the ground circuit end to end

• If 2 ohms or greater, repair the open/high resistance in the circuit
• If less than 2 ohms, repair the open/high resistance in the ground connection.

If less than 10 ohms

3. Ignition ON.
4. Test for 11-13 V at the vehicle harness connector between signal circuit terminal 3 and ground.

If not between 11-13 V

1. Ignition OFF, disconnect the connector at the BCM.
2. Test for infinite resistance between the signal circuit and ground.

• If less than infinite resistance, repair the short to ground in the circuit.
• If infinite resistance.

3. Test for less than 2 ohms in the signal circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the BCM.

If between 11-13 V

5. Ignition OFF, connect the harness connector at the S3 Transmission Shift Lever.
6. Test for voltage between the S3 Transmission Shift Lever connector signal circuit terminal 3 and ground, by back probing the connector, for the conditions listed below.

• 2.0-4.6 V - Plus button pressed
• 5.1-7.3 V - Minus button pressed
• 8.0-10.6 V - Neither button pressed

If voltage values are not correct

Replace the S3 Transmission Shift Lever.

If voltage values are correct

7. Replace the K9 Body Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Transmission Control Replacement for Transmission Shift Lever replacement
• Control Module References - for Body Control Module replacement, programming and setup

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