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
- Lost Communication with Multi-Axis Acceleration Sensor Module on Powertrain Expansion CAN Bus
DTC U1827 00
- Lost Communication with Steering Angle Sensor Module on Powertrain Expansion CAN Bus
Diagnostic Fault Information
Circuit/System Description
The Electronic Brake Control Module activates the other devices connected to the chassis high speed GMLAN serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The Electronic Brake Control Module, Rear Differential Clutch Control Module, Multi-Axis Acceleration Sensor, and Steering Wheel Angle Sensor are connected to the chassis high speed GMLAN serial data circuits.
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 device availability has not been received.
* Rear Differential Clutch Control Module detects an invalid signal from Multi-Axis Acceleration Sensor 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 device which is not communicating.
* If there are multiple non-communicating devices choose the one closest to the Electronic Brake Control Module.
Reference Information
Schematic Reference
* Data Communication Schematics 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 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 Control Module References for scan tool information
Circuit/System Verification
1. Refer to the DTC Descriptors to determine the device that is not communicating.
2. Verify that DTC U0073, U2100, U0074, U0077, U0078, U1814, U2099, B1325, B1330, B1370, B1380, B1424, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, or P0562 is not set.
• If any of the DTCs are set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
• If none of the DTCs are set
3. Refer to Circuit/System Testing.
Circuit/System Testing
Note: Terminal and connector identifiers will be different depending on the individual device being tested. Use Schematic Reference and Connector End View Reference to identify device's connector, B+, ignition, ground, and serial data circuit terminals.
1. Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters (9.8 feet) away from vehicle. Disconnect all harness connectors at the device that is not communicating. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 6 and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
3. Ignition ON.
4. Verify a test lamp illuminates between the ignition circuit terminal 5 and ground.
• If the test lamp does not illuminate
1. Ignition OFF, disconnect the harness connectors at the K17 Electronic Brake Control Module.
2. Test for infinite resistance between the ignition circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the ignition circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K17 Electronic Brake Control Module.
• If the test lamp illuminates
5. Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters (9.8 feet) away from vehicle. Disconnect the harness connectors at the device setting the DTC. It may take up to 2 minutes for all vehicle systems to power down.
6. Test for less than 2 ohms in each of the serial data circuits end to end between the non-communicating device and the device setting the DTC.
• If 2 ohms or greater
Repair the open/high resistance in the serial data circuit between the non communicating device and the device setting the DTC or a serial data splice pack.
• If less than 2 ohms
7. Replace the device that is not communicating.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* GMLAN Wiring Repairs GMLAN Wiring Repairs
* Control Module References Control Module References for device replacement, programming and setup