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U1826





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 00

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Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B"

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 00

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Lost Communication With Steering Angle Sensor Module on Bus "B"

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 other control modules connected to the CAN serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The EBCM, Yaw and Lateral Accelerometer Sensor, and the Steering Wheel Position Sensor are the only control modules connected to the CAN bus serial data circuits.

Conditions for Running the DTC

* Ignition is ON and 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 is missing or invalid.

Action Taken When the DTC Sets

* The EBCM disables the VSES for the duration of the ignition cycle.

* The driver information center (DIC) displays the STABILITRAK Off message.

* The ABS/TCS remains functional.

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 control 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

DTC U1826

1. Ignition OFF, disconnect the harness connector at the Yaw and Lateral Accelerometer Sensor.

2. Test for less than 10 ohms between the ground circuit terminal 6 and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 5 and ground.

If the test lamp does not illuminate, test the ignition 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 and the Steering Wheel Position Sensor.

5. Ignition ON, test for less than 1 V between each serial data circuit terminal listed below and ground.

* EBCM serial data circuit terminal 33

* EBCM serial data circuit terminal 21

If greater than the specified range, test the appropriate serial data circuit for a short to voltage.

6. Ignition OFF, test for infinite resistance between each serial data circuit terminal listed below and ground.

* EBCM serial data circuit terminal 33

* EBCM serial data circuit terminal 21

If less than the specified range, test the appropriate serial data circuit for a short to ground.

7. Test for less than 2 ohms in each serial data circuit between the Yaw and Lateral Accelerometer Sensor and the EBCM.

* Yaw and Lateral Accelerometer Sensor serial data circuit terminal 3 and EBCM serial data circuit terminal 33

* Yaw and Lateral Accelerometer Sensor serial data circuit terminal 1 and EBCM serial data circuit terminal 21

If greater than the specified range, test the appropriate serial data circuit for an open/high resistance.

8. Test for infinite resistance between the EBCM serial data circuit terminal 33 and the EBCM serial data circuit terminal 21.

If less than the specified range, test the serial data circuits for a short together.

9. If all circuits test normal, replace the Yaw and Lateral Accelerometer Sensor.

DTC U1827

1. Ignition OFF, disconnect the harness connector at the Steering Wheel Position Sensor.

2. Test for less than 10 ohms between the ground circuit terminal 6 and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 5 and ground.

If the test lamp does not illuminate, test the ignition 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 and the Yaw and Lateral Accelerometer Sensor.

5. Ignition ON, test for less than 1 V between each serial data circuit terminal listed below and ground.

* EBCM serial data circuit terminal 33

* EBCM serial data circuit terminal 21

If greater than the specified range, test the appropriate serial data circuit for a short to voltage.

6. Ignition OFF, test for infinite resistance between each serial data circuit terminal listed below and ground.

* EBCM serial data circuit terminal 33

* EBCM serial data circuit terminal 21

If less than the specified range, test the appropriate serial data circuit for a short to ground.

7. Test for less than 2 ohms in each serial data circuit between the Steering Wheel Position Sensor and the EBCM.

* Steering Wheel Position Sensor serial data circuit terminal 3 and EBCM serial data circuit terminal 33

* Steering Wheel Position Sensor serial data circuit terminal 1 and EBCM serial data circuit terminal 21

If greater than the specified range, test the appropriate serial data circuit for an open/high resistance.

8. Test for infinite resistance between the EBCM serial data circuit terminal 33 and the EBCM serial data circuit terminal 21.

If less than the specified range, test the serial data circuits for a short together.

9. 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 Angle Sensor Replacement Removal and Replacement

* Control Module References Control Module References for control module replacement, programming and setup