U1826
DTC U1826
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
- Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B"
DTC U1826 71
- Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Invalid Data
DTC U1826 72
- Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Message Counter Incorrect
DTC U1826 7F
- Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Bus Signal Erratic
Diagnostic Fault Information
Circuit/System Description
The electronic brake control module (EBCM) activates the 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 and Yaw and Lateral Accelerometer Sensor are 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 control module which is not communicating.
* If there are multiple non-communicating control modules choose the one closest to the EBCM.
Reference Information
Schematic Reference
* Data Communication Schematics Electrical Diagrams
* Antilock Brake System Schematics
* Control Module References Control Module References
Connector End View Reference
Component Connector End Views Connector Views
Description and Operation
ABS 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
1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connector at the Yaw and Lateral Accelerometer Sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohm between the Yaw and Lateral Accelerometer 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 and Lateral Accelerometer 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. Ignition ON, test for less than 1 V between each Yaw and Lateral Accelerometer Sensor serial data circuit terminal listed below and ground.
* Serial data circuit terminal 2
* Serial data circuit terminal 3
• If greater than the specified value, test the appropriate serial data circuit for a short to voltage.
6. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for infinite resistance between each Yaw and Lateral Accelerometer Sensor serial data circuit terminal listed below and ground.
* Serial data circuit terminal 2
* Serial data circuit terminal 3
• If not the specified value, test the appropriate serial data circuit for a short to ground.
7. Test for infinite resistance between the Yaw and Lateral Accelerometer Sensor serial data circuit terminal 2 and terminal 3.
• If not the specified value, test the serial data circuits for a short together.
8. Test for less than 2 ohm in each serial data circuit between the Yaw and Lateral Accelerometer Sensor and the EBCM.
* Yaw and Lateral Accelerometer Sensor serial data circuit terminal 2 and EBCM serial data circuit terminal 33
* Yaw and Lateral Accelerometer Sensor serial data circuit terminal 3 and EBCM serial data circuit terminal 21
• If greater than the specified value, test the appropriate serial data circuit for an open/high resistance.
9. If all circuits test normal, replace the Yaw and Lateral Accelerometer 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
* Control Module References Control Module References for control module replacement, setup, and programming