Diagnostic Instructions

DTC Descriptor

DTC U1826 71: Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Invalid Serial Data Received

DTC U1826 72: Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Alive Counter Incorrect/Not Updated

DTC U1826 7F: Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Erratic

DTC U1827 71: Lost Communication With Steering Angle Sensor Module on Bus "B" Invalid Serial Data

DTC U1827 72: Lost Communication With Steering Angle Sensor Module on Bus "B" Alive Counter Incorrect/Not Updated

DTC U1827 74: Lost Communication With Steering Angle Sensor Module on Bus "B" Value of Signal Protection Calculation Incorrect

DTC U1827 7F: Lost Communication With Steering Angle Sensor Module on Bus "B" Erratic

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Steering Wheel Position Sensor Can Bus High Serial Data	U1827 7F	U1827 7F	U1827 7F	U1827 7F
Steering Wheel Position Sensor Can Bus Low Serial Data	U1827 7F	1827 7F	U1827 7F	U1827 7F
Vehicle Yaw Sensor Can Bus High Serial Data	U1826 7F	U1826 7F	U1826 7F	U1826 7F
Vehicle Yaw Sensor Can Bus Low Serial Data	U1826 7F	U1826 7F	U1826 7F	U1826 7F
Vehicle Yaw Sensor Low Reference	U1826 7F	U1826 7F	U1826 7F	U1826 7F
Steering Wheel Position Sensor Low Reference	U1827 7F	U1827 7F	U1827 7F	U1827 7F
Vehicle Yaw Sensor 12-volt Reference	U1826 7F	U1826 7F	U1826 7F	U1826 7F
Steering Wheel Position Sensor 12-volt Reference	U1827 7F	U1827 7F	U1827 7F	U1827 7F
Defective Yaw/Lat Sensor U1826 71, U1826 72 Defective Steering Angle Sensor U1827 71, U1827 72, U1826 74

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.

Conditions for Running the DTC

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

Conditions for Clearing the DTC

Diagnostic Aids

Reference Information

Schematic Reference

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

Yaw Rate Sensor DTC U1826

1. Use the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested.
2. Ignition OFF, disconnect the harness connector at the Yaw Rate Sensor.
3. Ignition ON, verify that a test lamp illuminates between the Yaw Rate Sensor voltage (12-volt ref) circuit terminal 1 and ground.

⇒	If the test lamp does not illuminate, test the circuit for a short to ground, or open/high resistance. If the circuit tests normal, replace the EBCM.

4. Ignition OFF, test for less than 5 ohms between the Yaw Rate Sensor low reference circuit terminal 6 and ground.

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

5. Test for less than 1 ohm in the CAN bus serial data circuits between the Yaw Rate Sensor terminals 3 and 2, and the EBCM connector 21 and 33.

⇒	If greater than 1 ohm, test the serial data circuits for open/high resistance.

6. If all circuits test normal, replace the yaw rate sensor.

Steering Wheel Position Sensor (Steering Angle Sensor) DTC U1827

1. Use the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested.
2. Ignition OFF, disconnect the harness connector at the Steering Wheel Position Sensor.
3. Ignition ON, verify that a test lamp illuminates between the Steering Wheel Position Sensor voltage (12-volt ref) circuit terminal 5 and ground.

⇒	If the test lamp does not illuminate, test the circuit for a short to ground, or open/high resistance. If the circuit tests normal, replace the Steering Wheel Position Sensor.

4. Ignition OFF, test for less than 5 ohms between the Steering Wheel Position Sensor low reference circuit terminal 6 and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the Steering Wheel Position Sensor.

5. Test for less than 1 ohm in the CAN bus serial data circuits between the Steering Wheel Position Sensor terminal 2 and 3, and the Yaw Rate Sensor terminal 5 and 4.

⇒	If greater than 1 ohm, test the serial data circuits for open/high resistance.

6. If all circuits test normal, replace the Steering Wheel Position Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.