U1651
DTC U1651
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 Descriptor
DTC U1651 00
- Chassis System Dedicated Bus Sensor Malfunction
Diagnostic Fault Information
Circuit Description
The yaw and lateral accelerometer sensor communicates to the electronic brake control module (EBCM) through a dedicated CAN Bus serial data circuit. Any fault on either or both CAN Bus circuits will cause DTC U1651 to be set in the EBCM module.
Conditions for Running the DTC
The system voltage is between 9-16 V.
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter module availability has not been received on one or both CAN Bus serial data circuits.
Action Taken When the DTC Sets
The vehicle stability system will not function.
Conditions for Clearing the DTC
* A current DTC clears when the malfunction is no longer present.
* A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
Diagnostic Aids
* Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios:
- A control module on the data communication circuit was disconnected while the communication circuit is awake.
- Power to one or more modules was interrupted during diagnosis.
- A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold.
- Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time.
- If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
* A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
* Some devices may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no device output voltage circuit is shorted to ground before replacing the device.
Reference Information
Schematic Reference
* Data Communication Schematics Electrical Diagrams
* Antilock Brake System Schematics [1][2]Antilock Brakes / Traction Control Systems
Connector End View Reference
Component Connector End Views Connector End Views By Name
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
With a scan tool, verify that all of the vehicle stability enhancement system (VSES) data is present in the EBCM module data list.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector of the yaw and lateral accelerometer sensor.
2. Test for less than 10 ohm between the low reference circuit terminal and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal and ground.
• If the test lamp does not illuminate, test the ignition 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 3 V at the appropriate CAN bus terminals:
• If greater than the specified range, test the circuits for a short to voltage.
6. Test for greater than 5 ohm between the appropriate CAN bus connector terminals and ground:
• If less than the specified range, test the circuits for a short to ground.
7. Test for greater than 5 ohm between appropriate CAN bus terminals.
• If less than the specified range, test for a short between the CAN bus serial data circuits.
8. Test for less than 5 ohm between sensor terminal and EBCM terminal for each individual CAN bus circuit:
• If greater than the specified range, test the appropriate serial data circuit for an open/high resistance.
9. If all circuits test normal, replace the yaw and lateral accelerometer sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Vehicle Longitudinal Accelerometer Replacement Service and Repair
* Control Module References Control Module References for control module replacement, setup, and programming