C0186

DTC C0186

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptor
DTC C0186 55
- Lateral Accelerometer Circuit Expected Number of Transition/Events Exceeded


DTC C0186 5A
- Lateral Accelerometer Plausibility Failure


DTC C0186 0F
- Lateral Accelerometer Circuit Erratic




Diagnostic Fault Information






Circuit/System Description

The lateral accelerometer and the yaw rate 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.


Conditions for Running the DTC

The ignition switch is in the ON position.


Conditions for Setting the DTC

* The yaw/lateral combination sensor fails an internal self test.
* Communication is lost between the EBCM and the yaw/lateral combination sensor.



Action Taken When the DTC Sets

One or more of the following actions may occur:

* The vehicle stability enhancement system (VSES) is disabled.
* Traction control system (TCS) is disabled.
* The TCS/VSES indicators illuminate.
* The driver information center (DIC) displays the Service Traction Control, and or Service Stabilitrak message.



Conditions for Clearing the DTC

* The condition for the DTC is no longer present.
* The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.



Reference Information
Schematic Reference

Antilock Brake System Schematics ([1][2]Antilock Brakes / Traction Control Systems)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

ABS Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for Scan Tool Information


Circuit/System Verification

Ignition ON, observe the scan tool yaw rate and lateral accelerometer sensor parameter. The reading should be the same on all sensors when driving in a straight line at a constant speed greater than 20 km/h (13 mph), on a flat level road, and will vary as the vehicle changes direction.


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the Yaw Rate/Lateral Accelerometer sensor.
2. Test for less than 1 ohm of resistance between the ground circuit terminal 6 and ground.

• If greater than the specified range, test for an open/high resistance in the ground circuit. If the circuit tests normal, replace the yaw rate/lateral accelerometer sensor.

3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 1 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 yaw rate/lateral accelerometer sensor.

4. Ignition OFF, disconnect the harness connector at the EBCM.
5. Ignition ON, test for 0 volts between the communication circuit terminal 21 and ground.

• If greater than the specified value, test the communication circuit for a short to voltage.

6. Test for 0 volts between the communication circuit terminal 33 and ground.

• If greater than the specified value, test the communication circuit for a short to voltage.

7. Ignition OFF, test for infinite resistance between the communication circuit terminal 21 and ground.

• If not the specified value, test the communication circuit for a short to ground.

8. Test for infinite resistance between the communication circuit terminal 33 and ground.

• If not the specified value, test the communication circuit for a short to ground.

9. Test for less than 1 ohm between the communication circuit terminals 21 and terminal 3.

• If greater than the specified range, test the communication circuit for an open/high resistance.

10. Test for less than 1 ohm between the communication circuit terminals 33 and terminal 2.

• If greater than the specified range, test the communication circuit for an open/high resistance.

11. Test for infinite resistance between the communication circuit 21 and the communication circuit 33.

• If not the specified value, test the communication circuits for a short together.

12. If all circuits test normal, replace the Yaw Rate/Lateral sensor.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Brake Pressure Modulator Valve Replacement (Service and Repair)
* Electronic Brake Control Module Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for EBCM replacement, setup, and programming