Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC U1826 71: Lost Communication With Multi-Axis Acceleration Sensor Module on Bus "B" Invalid Serial Data ReceivedDTC 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 71, U1827 72, U1827 7F | -- | U1827 7F |
Steering Wheel Position Sensor Can Bus Low Serial Data | -- | U1827 71, U1827 72, 1827 7F | -- | U1827 7F |
Vehicle Yaw Sensor Can Bus High Serial Data | -- | U1826 71, U1826 72, U1826 74, U1826 7F | -- | U1826 7F |
Vehicle Yaw Sensor Can Bus Low Serial Data | -- | U1826 71, U1826 72, U1826 74, U1826 7F | -- | U1826 7F |
Vehicle Yaw Sensor Low Reference | -- | 1 | -- | -- |
Steering Wheel Position Sensor Low Reference | -- | 1 | -- | -- |
Vehicle Yaw Sensor 12-Volt Reference | 1 | 1 | -- | -- |
Steering Wheel Position Sensor 12-Volt Reference | 1 | 1 | -- | -- |
1. Circuit Inoperative | ||||
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, Supervisory Control Module (SCM), Electronic Suspension Control Module (ESC), Power Steering Control Module (PSCM), Yaw Rate/Lateral Accelerometer Sensor, and the Steering Angle or Steering Wheel Position Sensor are the only modules 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 .
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.
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 module which is not communicating. |
| • | If there are multiple non-communicating modules choose the one closest to the EBCM. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
Yaw Rate Sensor DTC U1826
- Use the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested.
- Ignition OFF, disconnect the harness connector at the Yaw Rate Sensor.
- Ignition ON, verify that a test lamp illuminates between the Yaw Rate Sensor voltage (12-volt ref) circuit terminal 4 and ground.
- Ignition OFF, test for less than 5 ohms between the Yaw Rate Sensor low reference circuit terminal 1 and ground.
- Test for less than 1 ohm in the CAN bus serial data circuits between the Yaw Rate Sensor and the SCM.
- If all circuits test normal, replace the SCM.
| ⇒ | 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 yaw/accelerometer sensor. |
| ⇒ | If greater than the specified value, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the yaw/accelerometer sensor. |
| ⇒ | If greater than 1 ohm, test the serial data circuits terminals 2 and 3 for open/high resistance. |
Steering Wheel Position Sensor (Steering Angle Sensor) DTC U1827
- Use the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested.
- Ignition OFF, disconnect the harness connector at the Steering Wheel Position Sensor.
- Ignition ON, verify that a test lamp illuminates between the Steering Wheel Position Sensor voltage (12-volt ref) circuit terminal 5 and ground.
- Ignition OFF, test for less than 5 ohms between the Steering Wheel Position Sensor low reference circuit terminal 6 and ground.
- Test for less than 1 ohm in the CAN bus serial data circuits between the Steering Wheel Position Sensor and the Yaw Rate Sensor.
- If all circuits test normal, replace the SCM.
- Test for less than 1 ohm in the CAN bus serial data circuits between the Steering Wheel Position Sensor and the Active Front/Power Steering Control Module.
- If all circuits test normal, replace the steering angle position sensor.
| ⇒ | 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. |
| ⇒ | If greater than the specified value, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the Steering angle Position Sensor. |
| ⇒ | If greater than 1 ohm, test the serial data circuits terminals 3 and 1 for open/high resistance. |
| ⇒ | If greater than 1 ohm, test the serial data circuits terminals 4 and 2 for open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for module replacement, setup, and programming |
