U1827
DTC U1826 or U1827
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 U1826 71
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Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Invalid Serial Data Received
DTC U1826 72
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Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Alive Counter Incorrect/Not Updated
DTC U1826 7F
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Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Erratic
DTC U1827 71
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Lost Communication With Steering Angle Sensor Module on Bus "B" Invalid Serial Data
DTC U1827 72
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Lost Communication With Steering Angle Sensor Module on Bus "B" Alive Counter Incorrect/Not Updated
DTC U1827 74
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Lost Communication With Steering Angle Sensor Module on Bus "B" Value of Signal Protection Calculation Incorrect
DTC U1827 7F
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Lost Communication With Steering Angle Sensor Module on Bus "B" Erratic
Diagnostic Fault Information
Circuit/System Description
The electronic brake control module (EBCM) activates the other modules connected to the CAN serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The EBCM, Yaw Rate Sensor, and the Steering Angle or Steering Wheel Position Sensor are the only modules connected to the CAN bus serial data circuits. For more information on CAN bus serial data refer to Data Link Communications Description and Operation Description and Operation.
Conditions for Running the DTC
* The system voltage is between 9-16 V.
* The vehicle power mode master requires serial data communication to occur.
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter module availability has not been received.
Action Taken When the DTC Sets
* The vehicle stability enhancement system (VSES), if equipped, and traction control system (TCS) will not function.
* System OFF lamps will illuminate for these systems.
Conditions for Clearing the DTC
* A current DTC clears when the malfunction is no longer present.
* A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
Diagnostic Aids
* Use the DTC Descriptor list above to determine the module which is not communicating.
* If there are multiple non-communicating modules choose the one closest to the EBCM.
Reference Information
Schematic Reference
* Data Communication Schematics [1][2]Electrical Diagrams
* Antilock Brake System Schematics [1][2]Antilock Brakes / Traction Control Systems
* Control Module References Control Module References
Connector End View Reference
Component Connector End Views A/C Compressor Clutch
Description and Operation
ABS Description and Operation 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
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Testing
Yaw Rate Sensor DTC U1826
1. Ignition OFF, disconnect the harness connector at the Yaw Rate Sensor.
2. Test for less than 5 ohms between the Yaw Rate Sensor ground circuit terminal 6 and ground.
• If greater than the specified value, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the Yaw Rate Sensor voltage (12 V reference) circuit terminal 1 and ground.
• If the test lamp does not illuminate, test the circuit for a short to ground, or an open/high resistance. If the circuit tests normal, replace the EBCM.
4. Ignition OFF, disconnect the harness connector at the EBCM.
5. Test for less than 1 ohms in each pair of serial data circuits between the Yaw Rate Sensor and the EBCM:
* Yaw Rate Sensor serial data circuit terminal 2 and EBCM serial data circuit terminal 33
* Yaw Rate Sensor serial data circuit terminal 3 and EBCM serial data circuit terminal 21
• If greater than 1 ohms, test the Yaw Rate Sensor serial data circuits terminals 2 and 3 for an open/high resistance.
6. If all circuits test normal, replace the Yaw Rate Sensor.
Steering Wheel Position Sensor (Steering Angle Sensor) DTC U1827
1. Ignition OFF, disconnect the harness connector at the Steering Wheel Position Sensor.
2. Test for less than 5 ohms between the Steering Wheel Position Sensor ground circuit terminal 1 and ground.
• If greater than the specified value, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the Steering Wheel Position Sensor voltage (12 V reference) circuit terminal 2 and ground.
• If the test lamp does not illuminate, test the circuit for a short to ground, or an open/high resistance. If the circuit tests normal, replace the EBCM.
4. Ignition OFF, disconnect the harness connector at the Yaw Rate Sensor.
5. Test for less than 1 ohms in each pair of serial data circuits between the Steering Wheel Position Sensor and the Yaw Rate Sensor:
* Steering Wheel Position Sensor serial data circuit terminal 3 and Yaw Rate Sensor serial data circuit terminal 4
* Steering Wheel Position Sensor serial data circuit terminal 4 and Yaw Rate Sensor serial data circuit terminal 5
• If greater than 1 ohms, test the Steering Wheel Position Sensor serial data circuits terminals 3 and 4 for an open/high resistance.
6. If all circuits test normal, replace the Steering Wheel Position Sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* GMLAN Wiring Repairs GMLAN Wiring Repairs
* Vehicle Yaw Sensor with Vehicle Lateral Accelerometer Replacement Service and Repair
* Steering Wheel Position Sensor or Steering Shaft Lower Bearing Replacement Steering Wheel Position Sensor or Steering Shaft Lower Bearing Replacement
* Control Module References Control Module References for module replacement, setup, and programming