P1761

DTC P1761

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P1761
- Up and Down Shift Switch Signal Message Counter Incorrect

Circuit/System Description

When the shift lever is moved left of the D position, the transmission will enter sport mode. With the shift lever in this position, the transmission will enter manual mode if the gear shift lever is pressed forward or rearward. This allows the operator to select an upshift by pressing the gear shift lever forward, and downshift by pressing the gear shift lever rearward. The body control module (BCM) supplies battery voltage, ground, and a signal circuit to the shift controller. The shift controller has Hall-effect switches connected to a resistor array. When the lever is left of the D position, a voltage drop occurs across the resistor network. When the gear shift lever is pressed forward or rearward, 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 is constantly monitoring the serial data sent from the BCM for the correct number and sequence of counts for Tap Up and Tap Down function.

Conditions for Running the DTC

* Engine speed is 400-7,500 RPM for 5 s.

* Runs continuously when above condition is met.

Conditions for Setting the DTC

TCM detects the internal rolling count value does not match the expected BCM count, 3 times within 10 s.

Action Taken When the DTC Sets

* P1761 is a Type C DTC.

* TCM inhibits the Tap Up Tap Down function.

* TCM inhibits manual shifting of forward gears.

Conditions for Clearing the DTC

P1761 is a Type C DTC.

Reference Information

Schematic Reference

* Automatic Transmission Controls Schematics Electrical Diagrams

* Data Communication Schematics [1][2]Electrical Diagrams

* Body Control System Schematics [1][2]Body Control Systems

Connector End View Reference

* Component Connector End Views Outside Rearview Mirror - Driver

* Inline Harness Connector End Views X100

Description and Operation

* Transmission General Description Transmission General Description

* Transmission Component and System Description Transmission Component and System Description

* Electronic Component Description Electronic Component Description

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

Note:

* DTC P1761 is an informational DTC.

* Diagnose all other body control module DTCs prior to DTC P1761.

1. Verify there are no other body control module or communication DTCs set.

• If a DTC is set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

• If a DTC is not set

2. Complete the diagnosis by looking for a GMLAN circuit fault. Refer to Scan Tool Does Not Communicate with High Speed GMLAN Device Scan Tool Does Not Communicate with High Speed GMLAN Device.

• If a GMLAN circuit fault is found
Repair as necessary.

• If a GMLAN circuit fault is not found

3. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Perform the Transmission Adaptive Values Learn Transmission Adaptive Values Learn following all transmission repairs.

* Control Module References Control Module References for BCM and Control Solenoid Valve Assembly replacement, programming and setup.