P1876
DTC P1876
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptor
DTC P1876
- Up and Down Shift Enable Switch Circuit Low Voltage
Circuit/System Description
The 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 L (M) position and is deactivated in all other positions.
If the transmission control module (TCM) detects TAP enable switch Active and the IMS switch does not indicate L (M), DTC P1876 sets. DTC P1876 is a type C DTC.
Conditions for Running the DTC
* No TAP system DTCs P0815, P0816, or P0826.
* No IMS DTCs P1825 or P1915.
* No Communication DTC U0100.
* The engine speed is greater than 500 RPM for 5 seconds.
* The ignition voltage is between 8.6 volts and 19.0 volts.
Conditions for Setting the DTC
The Tap Up/Tap Down switch signal is Active when the IMS does not indicate L (M) for 2 seconds or greater 3 times during the same ignition cycle.
Action Taken When the DTC Sets
* DTC P1876 is a Type C DTC.
* The TCM disables Tap shift functions.
Conditions for Clearing the DIC/DTC
DTC P1876 is a Type C DTC.
Diagnostic Aids
If there are any IMS DTCs, then diagnose them first.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
* Transmission General Description (Transmission General Description)
* Electronic Component Description (Electronic Component Description)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Verify there are not IMS DTCs set.
• If IMS DTCs are set, diagnose them first.
2. Ignition ON, transmission in Park, observe the scan tool Driver Shift Control parameter. The reading should display Inactive.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the transmission shift lever.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal A and ground.
• If the test lamp does not illuminate, test the IGN circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
3. Verify the scan tool Driver Shift Request parameter indicates Invalid.
• If other than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
4. Ignition OFF, test for less than 10 ohms of resistance between the signal circuit terminal B and ground.
• If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the transmission shift lever.
Component Testing
1. Ignition OFF, disconnect the harness connector at the transmission shift lever.
2. Test for 6.74-6.94 K ohms of resistance between terminals A and B of the automatic transmission control.
• If not within the specified range, replace the transmission shift lever.
3. Test for 1.77-1.97 K ohms of resistance between terminals A and B of the automatic transmission control while pressing the upshift button.
• If not within the specified range, replace the transmission shift lever.
4. Test for 3.87-4.07 K ohms of resistance between terminals A and B of the automatic transmission control while pressing the downshift button.
• If not within the specified range, replace the transmission shift lever.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Important: Perform the Service Fast Learn Adapts (Programming and Relearning) following all transmission related repairs.
Control Module References (Programming and Relearning) for body control module (BCM) replacement, setup, and programming
Transmission Control Replacement (Transmission Control Replacement) for AT TAP shift switch replacement
Important: Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection).
Control Module References (Programming and Relearning) for control solenoid (w/body and TCM) valve assembly replacement, setup, and programming