Diagnostic Instructions

DTC Descriptors

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

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

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Sensor B+	U1826 72	U1826 7F, U1826 72	--	--
Yaw Sensor Can Bus High Serial Data	U1826 72, U1826 7F	U1826 71, U1826 72, U1826 7F	U1826 71	U1826 71
Yaw Sensor Can Bus Low Serial Data	U1826 72	U1826 71, U1826 72, U1826 7F	U1826 71	U1826 7F
Low Reference	--	U1826 71, U1826 72, U1826 7F	--	U1826 71

Circuit/System Description

The yaw rate and the lateral accelerometer sensors are combined into one sensor, external to the electronic brake control module (EBCM). The vehicle stability enhancement system (VSES) uses the lateral accelerometer input when calculating the desired yaw rate. The yaw rate/lat sensor communicates with the EBCM via discrete CAN Bus High and CAN Bus Low serial data circuits.

Conditions for Running the DTC

Ignition ON

Conditions for Setting the DTC

Action Taken When the DTC Sets

Conditions for Clearing the DTC

Reference Information

Schematic Reference

Antilock Brake System Schematics

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

1. Ignition OFF, disconnect the harness connector at the yaw/lat sensor.
2. Ignition OFF for 60 seconds, test for less than 5 ohm between the low reference circuit terminal 6 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the EBCM.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 1 and ground.

⇒	If the test lamp does not illuminate, test the B+ 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 volt between the following terminal listed below and ground at the EBCM harness connector.

•	CAN bus high serial data circuit terminal 33

•	CAN bus low serial data circuit terminal 21

⇒	If greater than the specified value, test the appropriate serial data circuit for a short to voltage.

6. Ignition OFF, test for infinite resistance between the following terminal listed below and ground at the EBCM harness connector.

•	CAN bus high serial data circuit terminal 33

•	CAN bus low serial data circuit terminal 21

⇒	If not the specified value, test the appropriate serial data circuit for a short to ground.

7. Test for less than 2 ohms between the following terminals listed below.

•	CAN bus high serial data circuit terminal 33 at the EBCM harness connector and terminal 2 at the yaw/rate sensor.

•	CAN bus low serial data circuit terminal 21 at the EBCM harness connector and terminal 3 at the yaw/rate sensor.

⇒	If greater than the specified range, test the appropriate serial data circuit for an open/high resistance.

8. Test for infinite resistance between the CAN bus high serial data circuit terminal 33 and the CAN bus low serial data circuit terminal 21 at the EBCM harness connector.

⇒	If not the specified value, test the serial data circuits for a short to each other.

9. If all circuits test normal, replace the vehicle yaw sensor with vehicle lateral accelerometer.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.