GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2009 🢒 Allure 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC C0187

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 Descriptor

DTC C0187: Lateral Accelerometer Circuit Range/Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Yaw and Lateral Accelerometer Sensor Signal Circuit

--

--

--

C0187

Circuit Description

The vehicle stability enhancement system (VSES) uses the lateral accelerometer input when calculating the desired yaw rate. The usable output voltage range for the lateral accelerometer 0.25-4.75 volts. The scan tool will report zero lateral acceleration as 2.5 volts with no sensor bias present.

The lateral accelerometer sensor bias compensates for sensor mounting alignment errors and electronic signal errors.

Conditions for Running the DTC
    • The ignition is ON.
    • The vehicle speed is greater than 40 km/h (25 mph).

Conditions for Setting the DTC
    • A reference lateral acceleration from the data of the yaw rate sensor, wheel speed sensors, and steering angle sensor is used to test the lateral accelerometer signal. If during stable driving conditions, the lateral accelerometer signal becomes larger than 0.26 g, the electronic brake control module (EBCM) controller will disregard the signal so that a false EBCM intervention is prevented. A malfunction is detected if this condition continues for more than 2 seconds.
    • Under normal driving conditions, the long time filtered driving direction is straight ahead. The long time filtered lateral accelerometer value is called the offset. If the offset value is higher than 0.23 g, a malfunction is detected. Malfunction time depends on driving distance, vehicle speed and the amount of malfunctioning later accelerometer signal.
    • The lateral accelerometer signal is limited to an electrical stop of 1.8 g. If the lateral accelerometer signal is greater than 1.5 g for more than 500 milliseconds, a malfunction is detected.
    • At a standstill, the range of the lateral accelerometer signal is less than 0.7 g. If the lateral accelerometer signal is greater than 0.7 g at standstill, a malfunction is detected.
    • Lateral accelerometer signal cannot change rapidly under normal driving conditions. If the lateral accelerometer signal is changing faster than 55 g per second, a malfunction is detected.

Action Taken When the DTC Sets

If equipped, the following actions occur:

    • The EBCM disables the traction control system (TCS)/VSES for the duration of the ignition cycle.
    • A malfunction DTC will set.
    • The antilock brake system (ABS) indicator turns ON.
    • The Stability Off indicator turns ON.

Conditions for Clearing the DTC
    • The condition for the DTC is no longer present.
    • A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids

Important:  Perform the steering angle sensor centering procedure after the diagnostic system check-vehicle is performed. Refer to Steering Angle Sensor Centering.

    • Find out from the customer under what condition was the DTC set. This information will help to duplicate the failure.
    • Check the vehicle for proper alignment. The car should not pull in either direction while driving straight on a level surface.
    • During diagnosis, park the vehicle on a level surface.
    • Check for malfunctioning EBCM and lateral accelerometer.
    • The snapshot function on the scan tool can help find an intermittent 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

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Verification

Ignition ON, verify the scan tool Lateral Acceleration G value in the scan tool VSES scan tool data. If the specified value displays one of the following, a malfunction has occurred:

    •  Under normal driving conditions, the long time filtered driving direction is straight ahead. The longtime filtered lateral accelerometer value is called the offset. The offset value is higher than 0.23 g.
    • The lateral accelerometer signal is limited to an electrical stop of 1.8 g. Verify the lateral accelerometer is not greater than 1.5 g for more than 500 milliseconds.
    • During stable driving conditions, the lateral accelerometer signal becomes larger than 0.26 g for more than 2 seconds.
    •  At standstill, the range of the lateral accelerometer signal is greater than 0.7 g.
    •  Lateral accelerometer signal cannot change rapidly under normal driving conditions. The lateral accelerometer signal is changing faster than 55 g per second.

Circuit/System Testing
  1. Ignition OFF, disconnect the EBCM harness connector at the Yaw and Lateral Accelerometer Sensor.
  2. Ignition OFF, with a DMM test for less than 5.0 ohms of resistance between the Vehicle Yaw and Lateral Accelerometer Sensor low reference circuit terminal 6 and ground.
    3. ⇒ If greater than the specified range, with the DMM test the low reference circuit terminal 6 for an open/high resistance. If the circuit tests normal, replace the EBCM.
  3. Ignition ON, with a DMM test for 2.3-2.7 volts between the Yaw and Lateral Accelerometer Sensor lateral accelerometer signal circuit terminal 5 and ground.
    4. ⇒ If less than the specified range, with the DMM test the lateral accelerometer signal circuit terminal 5 for a short to ground or an open/high resistance. If the circuit tests normal, replace the EBCM.
    ⇒If greater than the specified range, with the DMM test the lateral accelerometer signal circuit terminal 5 for a short to voltage. If the circuit tests normal, replace the EBCM.
  4. Ignition ON, with a DMM test for 2.3-2.7 volts between the Yaw and Lateral Accelerometer Sensor yaw rate signal circuit terminal 4 and ground.
    5. ⇒ If less than the specified range, with the DMM test the yaw rate signal circuit terminal 4 for a short to ground or an open/high resistance. If the circuit tests normal, replace the EBCM.
    ⇒If greater than the specified range, with the DMM test the yaw rate signal circuit terminal 4 for a short to voltage. If the circuit tests normal, replace the EBCM.
  5. With the DMM, verify the Vehicle Yaw and Lateral Accelerometer Sensor test control signal circuit terminal 2 range is less than 0.25 volts.
    6. ⇒ If greater than the specified value, test the signal circuit terminal 2 for a short to voltage. If the circuit tests normal, replace the EBCM.
  6. Install a 3A fused jumper wire between the Yaw and Lateral Accelerometer Sensor signal circuit terminal 2 and theYaw and Lateral Accelerometer Sensor 5-volt reference circuit terminal 3. With a DMM, verify the voltage value is greater than 4.75 volts.
    7. ⇒ If less than the specified value, test the signal circuit terminal 2 for a short to ground or an open/high resistance. If the circuit tests normal, replace the EBCM.
  7. If all circuits test normal, test or replace the Yaw and Lateral Accelerometer Sensor.

Component Testing
  1. Install a 3A fused jumper wire between the Yaw and Lateral Accelerometer Sensor 5-volt reference terminal 1 and 5 volts. Install a jumper wire between the low reference circuit terminal 6 and ground.
  2. Sweep the sensor through the entire range while monitoring the resistance between the signal circuit terminal 5 and the low reference circuit terminal 6. The voltage should vary between 0.25-4.75 volts without any spikes or dropouts.
    3. ⇒ If not within the specified range or is erratic, replace the Yaw and Lateral Accelerometer Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Vehicle Yaw Sensor with Vehicle Lateral Accelerometer Replacement
    •  Control Module References for EBCM replacement, setup, and programming