U0074
DTC U0074
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 U0074
-
Control Module Communication Bus B Off
DTC U0125
-
Lost Communication with Multi-Axis Acceleration Sensor Module
DTC U0126
-
Lost Communication with Steering Wheel Angle Sensor Module
Diagnostic Fault Information
Circuit/System Description
Control modules connected to the CAN bus serial data circuits are high speed serial data modules that monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.
The electronic brake control module activates the multi-axis acceleration sensor and the steering angle sensor, which are connected to the CAN serial data circuits, by applying voltage when the ignition key is in ACC, ON or START.
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 no communication condition exists on the CAN bus serial data between the electronic brake control module, the multi-axis acceleration sensor, and the steering angle sensor.
Action Taken When the DTC Sets
* The vehicle stability enhancement system, if equipped, and traction control system will not function.
* Service StabiliTrak and/or Service Traction Control lamps will illuminate.
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, without a repeat of the malfunction.
Diagnostic Aids
Ensure all inline connections are fully seated.
Reference Information
Schematic Reference
* Data Communication Schematics [1][2]Electrical Diagrams
* Antilock Brake System Schematics [1][2]Antilock Brakes / Traction Control Systems
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Data Link Communications 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. Ignition ON.
2. Verify that DTC U0125, U0126, and U0074 are not set.
• If only DTC U0125 is set
Refer to Circuit/System Testing - Only DTC U0125 is set.
• If only DTC U0126 is set
Refer to Circuit/System Testing - Only DTC U0126 is set.
• If DTC U0074 or both DTCs U0125 and U0126 are set
Refer to Circuit/System Testing - DTC U0074.
• If the DTCs listed are not set
3. All OK.
Circuit/System Testing
Only DTC U0125 is set
1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connectors at the B119 multi-axis acceleration sensor. 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 1 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 4 and ground.
• If the test lamp does not illuminate
Repair the open/high resistance in the circuit between the splice and the B119 multi-axis acceleration sensor.
• If the test lamp illuminates
5. Test for less than 130 ohms between the serial data circuits terminal 2 and 3.
• If 130 ohms or greater
1. Ignition OFF, disconnect the harness connectors at the B99 steering angle sensor.
2. Test for less than 2 ohms in each serial data circuit terminals listed below end to end.
* B119 multi-axis acceleration sensor terminal 2 and the B99 steering angle sensor terminal 2
* B119 multi-axis acceleration sensor terminal 3 and the B99 steering angle sensor terminal 4
• If greater than 2 ohms, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the B99 steering angle sensor.
• If less than 130 ohms
6. Replace the B119 multi-axis acceleration sensor.
Only DTC U0126 is set
1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connectors at the B99 steering angle sensor. 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
Repair the open/high resistance in the circuit between the splice and the B99 steering angle sensor.
• If the test lamp illuminates
5. Replace the B99 steering angle sensor.
DTC U0074
1. Ignition OFF and all vehicle systems OFF. Disconnect the harness connectors at the B99 steering angle sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Ignition ON.
3. 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 B119 multi-axis acceleration sensor, ignition ON.
2. Verify a test lamp illuminates between the ignition circuit and ground.
• If the test lamp illuminates, replace the B119 multi-axis acceleration sensor.
• If the test lamp does not illuminate
3. Ignition OFF, disconnect the harness connectors at the K17 electronic brake control module.
4. Test for infinite resistance between the ignition circuit and ground.
• If less than infinite resistance, repair the short ground on the circuit.
• If infinite resistance
5. Test for less than 2 ohms in the ignition circuit end to end between the B99 steering angle sensor and the K17 electronic brake control module terminal 32.
• If greater than 2 ohms, 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
4. Test for less than 4.5 V between each serial data circuit listed below and ground.
* Terminal 1
* Terminal 3
• If 4.5 V or greater
1. Ignition OFF, disconnect the harness connectors at the K17 electronic brake control module.
2. Test for less than 1 V between each serial data circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K17 electronic brake control module.
• If less than 4.5 V
5. Test for less than 4.5 V between each serial data circuit listed below and ground.
* Terminal 2
* Terminal 4
• If 4.5 V or greater
1. Ignition OFF, disconnect the harness connectors at the B119 multi-axis acceleration sensor.
2. Test for less than 1 V between each serial data circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the B119 multi-axis acceleration sensor.
• If less than 4.5 V
6. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.
7. Test for greater than 100 ohms between each serial data circuits listed below and ground.
* Terminal 1
* Terminal 3
• If 100 ohms or less
1. Ignition OFF, disconnect the harness connectors at the K17 electronic brake control module.
2. Test for infinite resistance between the serial data circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K17 electronic brake control module.
• If greater than 100 ohms
8. Test for greater than 100 ohms between each serial data circuit listed below and ground.
* Terminal 2
* Terminal 4
• If 100 ohms or less
1. Ignition OFF, disconnect the harness connectors at the B119 multi-axis acceleration sensor.
2. Test for infinite resistance between the serial data circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the B119 multi-axis acceleration sensor.
• If greater than 100 ohms
9. Test for 110-130 ohms between the serial data circuits terminal 1 and 3.
• If less than 110 ohms
1. Ignition OFF, disconnect the harness connectors at the K17 electronic brake control module.
2. Test for infinite resistance between the serial data circuits.
• If less than infinite resistance, repair the short between the circuits.
• If infinite resistance, replace the K17 electronic brake control module.
• If greater than 130 ohms
1. Ignition OFF, disconnect the harness connectors at the K17 electronic brake control module.
2. Test for less than 2 ohms in each serial data circuit terminals listed below end to end.
* B99 steering angle sensor terminal 1 and K17 electronic brake control module terminal 24
* B99 steering angle sensor terminal 3 and K17 electronic brake control module terminal 37
• If greater than 2 ohms, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K17 electronic brake control module.
• If between 110-130 ohms
10. Test for 110-130 ohms between the serial data circuits terminal 2 and 4.
• If less than 110 ohms
1. Ignition OFF, disconnect the harness connectors at the B119 multi-axis acceleration sensor.
2. Test for infinite resistance between the serial data circuits.
• If less than infinite resistance, repair the short between the circuits.
• If infinite resistance, replace the B119 multi-axis acceleration sensor.
• If greater than 130 ohms
1. Ignition OFF, disconnect the harness connectors at the B119 multi-axis acceleration sensor.
2. Test for less than 2 ohms in each serial data circuit terminals listed below end to end.
* B99 steering angle sensor terminal 2 and B119 multi-axis acceleration sensor terminal 2
* B99 steering angle sensor terminal 4 and B119 multi-axis acceleration sensor terminal 3
• If greater than 2 ohms, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the B119 multi-axis acceleration sensor.
• If between 110-130 ohms
11. Replace the B99 steering angle sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* GMLAN Wiring Repairs GMLAN Wiring Repairs
* Vehicle Yaw Sensor with Vehicle Lateral Accelerometer Replacement Service and Repair
* Steering Angle Sensor Replacement (LHD) Removal and Replacement
* Control Module References Control Module References for electronic brake control module replacement, programming and setup