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 00
-
Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B".
DTC U1827 00
-
Lost Communication With Steering Angle Sensor Module on Bus "B".
Diagnostic Fault Information
Circuit/System Description
The electronic brake control module (EBCM) activates the other modules connected to the Chassis CAN serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The EBCM, Rear Differential Clutch Control Module, Multi-Axis Acceleration Sensor Module, and the Steering Wheel Angle Sensor are connected to the Chassis 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 volts.
* 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.
* Rear differential clutch control module detects an invalid signal from Multi-Axis Acceleration Sensor Module and/or Steering Wheel Angle Sensor.
Action Taken When the DTC Sets
All wheel drive performance will be temporarily degraded.
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 Electrical Diagrams
* Antilock Brake System Schematics [1][2]Antilock Brakes / Traction Control Systems
* Control Module References Programming and Relearning
Connector End View Reference
Component Connector End Views Sunshade - Left Front
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 Programming and Relearning for scan tool information
Circuit/System Testing
Note:
Use the DTC Descriptors and Diagnostic Aids above to determine the control module which is not communicating and should be tested. Use the schematics to identify the following:
* Control modules the vehicle is equipped with
* Control module locations on the Chassis high speed GMLAN serial data circuits
* The control module serial data circuit terminals
1. Ignition OFF, disconnect the harness connector at the non communicating control module.
2. Test for less than 5 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 K17 electronic brake control module (EBCM).
4. Ignition OFF, test for less than 1 ohms in each serial data circuit between the non communicating control module and the control module setting the DTC.
• If greater than the specified range, test the serial data circuits for an open/high resistance.
5. If all circuits test normal, replace the non communicating control module.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* GMLAN Wiring Repairs GMLAN Wiring Repairs
* Control Module References Programming and Relearning for module replacement, setup, and programming