For 1990-2009 cars

### Circuit Description

The vehicle stability enhancement system (VSES) is activated by the electronic brake control module (EBCM) calculating the desired yaw rate and comparing it to the actual yaw rate input. The desired yaw rate is calculated from measured steering wheel position, vehicle speed, and lateral acceleration. The difference between the desired yaw rate and the actual yaw rate is the yaw rate error, which is a measurement of oversteer or understeer. If the yaw rate error becomes too large, the EBCM will attempt to correct the vehicle yaw motion by applying differential braking to the left or right front wheel.

The amount of differential braking applied to the left or right front wheel is based on both the yaw rate error and side slip rate error. The side slip rate error is a function of the lateral acceleration minus the product of the yaw rate and vehicle speed. The yaw rate error and side slip rate error are combined to produce the total delta velocity error. When the delta velocity error becomes too large and the VSES system activates, the driver steering inputs combined with the differential braking will attempt to bring the delta velocity error toward zero.

The VSES activations generally occur during aggressive driving, in the turns or bumpy roads without much use of the accelerator pedal. When braking during VSES activation, the brake pedal will feel different than the ABS pedal pulsation. The brake pedal pulsates at a higher frequency during VSES activation.

### DTC Descriptors

This diagnostic procedure supports the following DTC:

DTC C0186 Lateral Accelerometer Circuit

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description .

DTC Symptom | DTC Symptom Descriptor
--- | ---
00 | No Additional Information
08 | Signal Invalid
09 | Rate of Change Above Threshold
19 | Signal Amplitude Above Maximum
1A | Bias Level Out Of Range
52 | Compare Failure

### Conditions for Running the DTC

#### C0186 00, 09, and 1A

• | The ignition is ON.

• | The ignition voltage is greater than 8 volts.

#### C0186 08

• | The ignition is ON.

• | The ignition voltage is greater than 8 volts.

• | The vehicle speed is greater than 0 km/h (0 mph).

#### C0186 19

• | The ignition is ON.

• | The ignition voltage is greater than 8 volts.

• | The vehicle is stopped.

#### C0186 52

• | The ignition is ON.

• | The ignition voltage is greater than 8 volts.

• | DTC C0196 is not set.

• | The yaw rate is less than 8 degrees per second.

### Conditions for Setting the DTC

#### C0186 00

One of the following conditions exist:

• | The lateral accelerometer sensor input voltage is less than 0.15 volts.

• | The lateral accelerometer sensor input voltage is greater than 4.85 volts for 0.03 seconds.

#### C0186 08

The lateral accelerometer voltage does not increase at least 0.5 volts during the lateral accelerometer sensor self test.

#### C0186 09

The lateral jerk exceeds 11 g per second twice within 0.2 seconds.

#### C0186 19

The lateral acceleration is greater than 0.5 g for more than 1 second.

#### C0186 1A

Both of the following conditions exist:

• | The compensated bias value of the lateral accelerometer sensor is greater than 0.3 g.

• | The yaw rate is centered.

#### C0186 52

The slip rate error exceeds 0.5 g 60 times within one drive cycle.

### Action Taken When the DTC Sets

• | The EBCM disables the VSES for the duration of the ignition cycle.

• | The DIC displays the Service Stabilitrak message.

• | The ABS/TCS remains functional.

### Conditions for Clearing the DTC

• | The condition for the DTC is no longer present and the DTC is cleared with a scan tool.

• | The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

### Diagnostic Aids

The following conditions can cause this concern:

• | Improper steering alignment.

• | Open, short to ground, or short to voltage.

• | Internal lateral accelerometer failure.

• | EBCM internal failure.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Tests for the proper voltage output on the 5-volt reference circuit and the proper operation of the signal circuit.

2. Tests for possible low 5-volt reference output or a problem with the signal circuit.

3. Tests for a short to voltage on the 5-volt reference circuit. If a short to voltage exists, other DTCs may be set for the vehicle stability system.

4. Tests for a problem with the low reference circuit. If a short to voltage exists, other DTCs may be set for the vehicle stability system.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn OFF the ignition.
2. Disconnect the harness connector of the yaw and lateral accelerometer sensor.
3. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the yaw and lateral accelerometer sensor and the signal circuit of the yaw rate/lateral accelerometer sensor.
4. Turn ON the ignition, with the engine OFF.
5. With the scan tool, observe the yaw rate sensor input parameter.

Does the scan tool indicate that the yaw rate signal parameter is in between the specified voltage range?

4.5-5.5V

Go to Step 8

Go to Step 3

3 | With the 3-amp fused jumper wire still connected, does the scan tool indicate that the yaw rate sensor parameter is below the specified voltage value? | 4.5V | Go to Step 5 | Go to Step 4
4 | Test the 5-volt reference circuit of the yaw and lateral acceleration sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7
5 | Test the 5-volt reference circuit of the yaw and lateral acceleration sensor for the following conditions:

• | Open

• | Short to Ground

• | High Resistance

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 6

6 | Test the yaw rate signal circuit for the following conditions:

• | Open

• | Short to Ground

• | High Resistance

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

7 | Test the yaw rate signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11
8 | Test the 5 volt reference circuit of the yaw rate and lateral accelerometer sensor for the following conditions:

• | Open

• | Short to Voltage

• | High Resistance

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

9 | Inspect for poor connections at the harness connector of the yaw and lateral accelerometer sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10
10 | Replace the yaw and lateral acceleration sensor. Refer to Vehicle Yaw Sensor with Vehicle Lateral Accelerometer Replacement . Did you complete the replacement? | -- | Go to Step 12 | --
11 | Replace the electronic brake control module (EBCM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | --
12 |

1. Use the scan tool in order to clear DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK