MP 3023/3024-NQH - Transfer Case
DTC P2160 or P2161
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 Descriptors
DTC P2160
- Vehicle Speed Sensor (VSS) 2 Circuit Low Voltage
DTC P2161
- Vehicle Speed Sensor (VSS) 2 Circuit Intermittent
Diagnostic Fault Information
Circuit/System Description
The vehicle speed sensor (VSS) provides vehicle speed information to the engine control module (ECM). The VSS is a permanent magnet generator. The sensor is mounted in the transfer case facing the rear internal gear which is splined to the output shaft assembly. As the output shaft and internal gear rotate, the toothed rotor of the internal gear produces AC voltage as the rotor teeth pass through the magnetic field of the sensor. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The ECM converts the voltage to vehicle speed. The ECM uses the output shaft speed signal to determine shift timing, as well as transfer case range.
Conditions for Running the DTC
P2160
* No input speed sensor (ISS) DTCs P0716 or P0717.
* No output speed sensor (OSS) DTCs P0722 or P0723.
* No vehicle speed sensor (VSS) DTCs P2160 or P2161.
* The throttle position is greater than 5 percent and less than 99 percent.
* The transmission is not in Reverse Inhibit state.
* The transmission is not in PARK or NEUTRAL.
* The transmission is not performing garage shifting.
* No engine torque, throttle position, and turbine speed DTCs.
* The engine torque is greater than 60 Nm (44 lb ft) and less than 8192 Nm (6042 lb ft).
* The input speed is greater than 1000 RPM and less than 7500 RPM.
P2161
* The transmission is not performing garage shifting.
* The transmission is not in Reverse Inhibit state.
* The transmission is not in PARK or NEUTRAL.
* The engine speed is 1000 RPM or greater.
* No crank sensor or P2160 DTCs.
Conditions for Setting the DTC
P2160
* No speed signal from the transfer case speed sensor.
* The transfer case output shaft speed is 50 RPM or less.
P2161
* Loss of speed signal from the transfer case speed sensor.
* Output speed signal is increasing: current transfer case speed signal - last valid output speed greater than 475 RPM.
* Output speed signal is decreasing: current transfer case speed signal - last valid output speed less than 255 RPM.
Action Taken When the DTC Sets
* DTCs P2160 and P2161 are Type B DTCs.
* The TCM commands maximum line pressure.
* The TCM freezes transmission adaptive functions.
* The TCM calculates vehicle speed from the automatic transmission input shaft speed sensor and commanded gear.
Conditions for Clearing the DTC
DTCs P2160 and P2161 are Type B DTCs.
Diagnostic Aids
* The transfer case drain plug provides a good ground point.
* The EL-49742 - harness provides a good source for 12 V and ground.
* Inspect the rear internal gear teeth for damage.
* Visually inspect the VSS for cracks or damage.
* Ensure the VSS is properly torqued to the transfer case housing.
* This diagnostic relates to the VSS located in the transfer case and not the OSS located within the transmission.
Reference Information
Schematic Reference
* Transfer Case Control Schematics MP 3023/3024-NQH - Transfer Case
* Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
Transfer Case Description and Operation Transfer Case Description and Operation
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
Special Tools
* EL-49742 - Battery Voltage B+ and Ground Source Harness
* J 35616 - GM-Approved Terminal Test Kit
Circuit/System Verification
1. Raise and support the drive wheels.
2. Start and idle the engine.
3. Place the transmission in DRIVE.
4. Monitor VSS on the scan tool under engine data.
5. The VSS on the scan tool should be greater than 100 RPM.
Circuit/System Testing
1. Key OFF. Let sit for 2 minutes to ensure that the ECM shuts down.
2. Disconnect the X1 connector from the VSS. Using the J 35616-2A GY probes, test for less than 0.1 V between the following circuits and a good ground.
* VSS high signal circuit, VSS harness X1 pin A.
* VSS low signal circuit, VSS harness X1 pin B.
• If the voltage is greater than the specified value, test the affected circuit for a short to voltage. If all circuits and connections test normal, test the ECM for proper operation.
3. Key ON, engine OFF. Test for a diagnostic 2-3 V (low current) between the following circuits and a good ground.
* VSS high signal circuit, VSS harness X1 pin A.
* VSS low signal circuit, VSS harness X1 pin B.
• If the voltage is less than the specified value, test the affected circuit for an open/high resistance, short to ground or short together. If all circuits and connections test normal, test the ECM for proper operation.
• If the voltage is greater than the specified value, test the affected circuit for a short to voltage. If all circuits and connections test normal, test the ECM for proper operation.
4. Test the VSS for proper operation.
Component Testing
VSS
1. Key OFF.
2. Disconnect the X1 connector from the VSS. Using the J 35616-3 GY probes, test for 1200-2140 ohms between the VSS high signal circuit, VSS pin A, and the VSS low signal circuit, VSS pin B.
• If the resistance is outside the specified value, replace the VSS.
3. Test for greater than 10 M ohms between the following circuits and a good ground.
* VSS high signal circuit, VSS pin A.
* VSS low signal circuit, VSS pin B.
• If the resistance is below the specified value, Replace the VSS.
4. Block the front wheels. Raise and support the driver's side rear wheel. While rotating the raised wheel by hand, test for greater than 0.4 V AC between the VSS high signal circuit, VSS pin A, and the VSS low signal circuit, VSS harness pin B. The passenger side rear wheel takes more effort to turn. If both drive wheels are raised and unblocked, twice the effort will be required to reach 0.4 V AC. If the vehicle is sufficiently supported to safely place the transmission in neutral, less effort will be required to turn the raised wheel.
• If the AC voltage is below the specified value, replace the VSS.
ECM
1. Remove key from the ignition. Let sit for 2 minutes to ensure ECM shut down
2. Disconnect the X1 connector from the ECM. Using the J 35616-64B L-BU probes, test for 1200-2140 ohms between the VSS high signal circuit, ECM X1, pin 71 and the VSS low signal circuit, ECM X1, pin 72.
• If the resistance is below the specified value, test the affected circuits for being shorted together. If all circuits and connections test normal, test the VSS for proper operation.
• If the resistance is above the specified value, test the affected circuits for open/high resistance condition. If all circuits and connections test normal, test the VSS for proper operation.
3. Using the J 35616-64B L-BU probes, test for greater than 1 M ohms between the following circuits and a good ground.
* VSS high signal circuit, ECM harness X1 pin 71.
* VSS low signal circuit, ECM harness X1 pin 72.
• If the resistance is below the specified value, test the affected circuit for being shorted to ground. If all circuits and connections test normal, test the VSS for proper operation.
4. Reprogram the ECM. If the DTC continues to set, replace the ECM.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Ensure that the VSS is 500 RPM or greater for 3 seconds and does not change more than 500 RPM or greater for 3 seconds.
* Vehicle Speed Sensor Replacement MP 3010-NP0 - Transfer Case
* Control Module References Control Module References for ECM replacement, setup, and programming