For 1990-2009 cars

## ABS Description and Operation V275

### General System Description

The ABS/TCS/ESC systems integrate several functional units and provide the pressure volume flow required for the modulation of brake torque in response to wheel slip information supplied by the wheel speed sensors. The TCS system serves to produce a stabilizing torque at the driven wheel running with the highest slip, or to reduce slip at both driven wheels, thereby optimizing the utilization of adhesion of the other driven wheel or driven wheels. The ESC system stabilizes the vehicle in the event of a yawing motion of the vehicle which is not in correlation with the sensed steering angle. It serves to reconcile the yawing motion of the vehicle with the driver's intentions. As input variables for ESP control, the signals of a lateral acceleration sensor, a yaw rate sensor, a steering angle sensor and a pressure sensor are required in addition to the signals provided by the wheel speed sensors available for ABS/TCS control. In addition, these systems may integrate an electronic brake force distribution (EBD) system to regulate effective brake force at the rear wheels in place of the traditional proportional valve.

The MK60EC is based on a housing with solenoid valves, integrated pump and ECU. Each mbrake circuit incorporates pairs of valves (NO inlet valve/NC outlet valve) permitting the brake pressure to be modulated at the front wheels (individual wheel control) and at the rear wheels (select low control or stability control with ABS plus) in response to suitable electrical signals.

The TCS ICU is based on the ABS MK60EC with additional components in the valve block for braking intervention during TCS operation and active yaw control. The isolation valves with integrated pressure relief valve in the TCS valve block permit braking pressure for TCS/ESP control to be built up by means of the pump, by-passing the actuation unit. The electric shuttle valves (ESVs) change the suction connection of the pump from the low pressure accumulators to the TMC. The suction dampers optimize the suction performance of the pump, and minimizes the cut-out impact at the end of a TCS control cycle.

### Basic Knowledge Required

Before using this section, it is important that you have a basic knowledge of the following items. Without this basic knowledge, it will be difficult to use the diagnostic procedures contained in this section.

• | Basic Electrical Circuits : You should understand the basic theory of electricity and know the meaning of potential (voltage), current (amperes) and resistance (ohms). You should understand what happens in a circuit with open or shorted wire. You should be able to read and understand a wiring diagram.

• | Use of Circuit Test Tools : You should be familiar with a DMM, and be familiar with the meter controls and how to use them correctly. You should be able to measure voltage, resistance and current. You should know how to use jumper wire to bypass components for testing circuits.

### ABS System Components

The MK60EC antilock brake system (ABS) consists of a conventional hydraulic brake system plus antilock components. The conventional brake system includes a vacuum booster, master cylinder, front disc brakes, rear drum brakes, interconnecting hydraulic brake pipes and hoses, brake fluid level sensor and the brake warning lamp indicator.

The ABS components include a hydraulic unit, an hydraulic electronic control unit (HECU) , system fuse, four wheel speed sensors (one at each wheel), interconnecting wiring, ABS indicator, the de-coupled dynamic rear proportioning (DDRP) indicator (which is connected to the parking lamp) and the rear drum brakes.

The hydraulic unit with the attached electronic brake control module (EBCM) is located between the surge tank and the fire wall on the left side of the vehicle.

The basic hydraulic unit configuration consists of hydraulic check valves, 2 solenoid valves for each wheel, a hydraulic pump, 2 accumulators. The hydraulic unit controls hydraulic pressure to the front calipers and the rear wheel cylinders by modulating hydraulic pressure to prevent wheel lockup.

### Arrangement of the Functional Units

#### Valve Control

Only the isolation valve and the electric shuttle valve (ESV) for the controlled wheel shall be switched. If both wheels are controlled on one side of the vehicle, then both isolation valves/ESVs shall be switched. The isolation valves shall be switched on continuously. Refer the table for details on valve control during the pressure increase, hold and reduction phases.

Description | NO valve | NC valve | Isolation valve | ESV
--- | --- | --- | --- | ---
Pressure holding phase | Closed | Closed | Closed | Closed
Pressure buildup phase | Open | Closed | Closed | Open (1)
Pressure reduction phase | Closed | Open | Closed | Closed
(1) The ESV of the controlled wheel shall be opened at the same time as the NO valve, but remains open 14 ms longer than the NO valve.

### Hydraulic Electronic Control Unit (HECU)

The HECU performs the following primary functions:

In order to provide efficient braking and vehicle stability. In de-coupled dynamic rear proportioning (DDRP) system, power to the rear hold valve solenoid is provided from Ignition. If the following fault conditions are existing, the red brake warning lamp will be illuminated.

• | Monitor wheel speed sensor inputs.

• | Detect wheel slip tendencies.

• | Control the brake system while in the antilock control mode.

• | Monitor the system for proper electrical operation.

The HECU continuously checks the speed of each wheel to determine if any wheel is beginning to slip. If any wheel slip tendency is detected, the HECU commands appropriate valve positions to modulate brake fluid pressure in some or all of the hydraulic circuits to prevent wheel slip and provide optimum braking. The HECU continues to control pressure in individual hydraulic circuits until a slipping tendency is no longer present. Also the HECU continuously monitors the ABS for proper operation. If the HECU detects an error, it can disable the ABS function and turn on the ABS Warning Lamp in the instrument cluster. The HECU also controls the display of the ABS DTCs (Diagnostic Trouble Codes) while in diagnostic mode.

### Solenoid Relay

The solenoid relay, provides power to the pump motor and solenoids. The switch in the relay is normally open, but is commanded to close during initialization. The relay switch will remain closed for the remainder of the drive cycle as long as no DTCs set which required the switch to open. If a DTC sets which requires the relay to be commanded off, battery voltage will be removed from the pump motor and solenoids for the remainder of the current drive cycle and ABS cannot function. The relay is an integral part of the HECU and cannot be serviced separately.

### Wheel Speed Sensors And Rings

A wheel speed sensor is present at each wheel. The sensors transmit wheel speed information to the HECU by means of a small AC voltage. The signal is transmitted to the HECU through interface that can cause false or noisy wheel speed sensor input to the HECU.

### ABS Warning Lamp

The ABS warning lamp is located in the instrument cluster and will illuminate if a malfunction in the ABS is detected by the HECU. The ABS warning lamp informs the driver that a condition exists which results in turning off the anti-lock brake function. If only the ABS is warning lamp is on, normal braking with full power assist is available.

Conditions for the ABS warning lamp to turn on are as follows.

• | ABS malfunction detected. As previously described, the ABS warning lamp turns on when a problem has been found in the ABS.

• | Instrument panel cluster bulb check. When the ignition is turned to ON, the ABS warning lamp will turn on for approximately 3 seconds and then turn off.

### Brake Warning Lamp

The red brake warning lamp is in the instrument cluster and will illuminate to warn the abnormal condition in the brake system, which may result in reduced braking ability. The lamp will illuminate when the parking brake is applied or not fully released, or if the brake fluid level switch is closed (when the brake fluid is low in the master cylinder reservoir). When the brake fluid level switch is closed (low condition) a brake warning lamp will stay illuminated until the condition has been repaired. Also some failure modes in the system will illuminate the lamp to let the drivers know de-coupled dynamic rear proportioning (DDRP) is disabled

### Electronic Stability Control (ESC)

For control, braking forces are applied to the corresponding wheels of the vehicle which build up a torque opposing the yawing motion. This means that a defined pressure is applied to one or both wheels on the left-hand side of the vehicle if the yawing motion is clockwise, whereas pressure is applied to the wheel circuits on the right-hand side of the vehicle if the yawing motion is counterclockwise.

If the brakes are applied during ESP control, the wheel circuits in which the NO valves are closed in order to keep the wheels depressurized are raised to the pressure level corresponding to the tendum master cylinder (TMC) pressure by the EBCM opening the corresponding inlet valves (NO) accordingly (brake by wire). The pressure level of the controlled wheels is also raised within the physical limits in order to maintain the yawing moment in spite of brake pressure build-up.

The brake pressure in the TMC causes a corresponding increase of the opening pressure of the isolation valves (TMC pressure acts in the closing direction of the isolation valves, which are not pressure balanced). As a result, the pump raises the system pressure by the amount of the TMC pressure, which may lead to unacceptably high pressures in the hydraulic control unit (HCU) unless appropriate countermeasures are taken.

For this reason, the isolation valves are opened by the EBCM at TMC pressures 100 bar in order to limit the pressure. Further pressure build-up in the system by the pump is then impossible. The pressure for ESP control is now supplied by the TMC alone. Same as during ABS/TCS control, the pressure in the wheel circuits is modulated via the inlet and outlet valves. During the pressure reduction phases of the control cycle, the ESVs are closed so that the drained brake fluid can be returned to the braking system from the low pressure accumulators.

### Electronic Brake Force Distribution (EBD)

The EBD system further utilizes the efficiency of the ABS system by controlling the slip of the rear wheels in the partial braking range, and hence, optimizing the driving characteristics in partial braking operation. The brake force is moved closer to the maximum brake force utilization of the rear axle, and controlled electronically.

Upon entry into EBD, the pressure supply to the rear axle is shut off via the NO valves when the slip of at least one rear wheel exceeds a defined limit. Depending on the actual slip of the wheels, this may be followed by further metered pressure build-up pulses. The outlet valves are only used to reduce the pressure if a lock-up tendency is detected at the rear axle. Generally, the control algorithm attempts to achieve a maximum utilization of braking force with a minimum of valve activity (noise, pedal reaction). As the drained volumes are generally very small so that they can be buffered in the low pressure accumulator, the pump of the HCU is not required for the EBD function. After termination of EBD control, the brake fluid is drained from the low pressure accumulators into the brake fluid reservoir via a short operation of the pump.

### Hydraulic Brake Assist (HBA)

In the case of a very fast master cylinder pressure increase a panic braking situation is determined and the hydraulic brake assist (HBA) function is activated. The hydraulic pump and the isolation valves of both hydraulic circuits are activated. The wheel pressures then increase above the master cylinder pressure. The pressure offset feature enabled in the configuration of the HBA allows a certain brake increase by applying an additional pressure offset during the HBA activity in stead of pushing the system always into ABS. This pressure offset depends on the pressure gradient reached during the HBA activation following the simple rule: the faster the driver brakes the more support, i.e. offset, provided.

If the wheel pressures reach the locking pressure the normal ABS function controls the stability of the wheels by switching the inlet (NO) and outlet (NC) valves. Thus, the HBA activation has the same effect as if the driver is braking with an increased pedal force which is sufficient to reach the locking pressure.

If the pedal force is significantly decreased, the HBA function classifies this as the drivers intention to end the full braking. Therefore, at the end of an HBA event, a pressure equalization between the wheel brakes and the master cylinder pressure will occur. This is achieved by performing a pulsed opening of the isolation valves.

## ABS Description and Operation Except V275

#### Hydraulic Diagram

(1) | Reservoir
(2) | Master Cylinder
(3) | Inlet Valve
(4) | Outlet Valve
(5) | Damper
(6) | Pump
(7) | Left Front
(8) | Right Rear
(9) | Left Rear
(10) | Accumulator
(11) | Right Front

The purpose of the MGH-25 antilock brake system (ABS) is to minimize wheel slip during heavy braking. MGH-25 performs this function by monitoring the speed of each wheel and controlling the brake fluid pressure to each wheel independently during a braking event. This allows the driver to retain directional stability and better steering capability.

### Basic Knowledge Required

Before using this section, it is important that you have a basic knowledge of the following items. Without this basic knowledge, it will be difficult to use the diagnostic procedures contained in this section.

• | Basic electrical circuits--You should understand the basic theory of electricity and know the meaning of potential, voltage, current, amperes, and resistance, ohms. You should understand what happens in a circuit with open or shorted wire. You should be able to read and understand a wiring diagram.

• | Use of circuit test tools--You should be familiar with a digital multimeter (DMM), and be familiar with the meter controls and how to use them correctly. You should be able to measure voltage, resistance, and current. You should know how to use jumper wire to bypass components for testing circuits.

### Antilock Brake System (ABS) System Components

Warning: Refer to ABS Component Handling Warning in the Preface section.

The MGH-25 ABS consists of a conventional hydraulic brake system plus antilock components. The conventional brake system includes a vacuum booster, master cylinder, front disc brakes, rear drum brakes, interconnecting hydraulic brake pipes and hoses, brake fluid level sensor, and the brake warning lamp indicator.

The antilock brake system (ABS) components include a hydraulic unit, an electronic brake control module (EBCM), system fuse, 4 wheel speed sensors, 1 at each wheel, interconnecting wiring, ABS indicator, the de-coupled dynamic rear proportioning (DDRP) indicator which is connected to the parking lamp, and the rear drum brakes. For the general layout of this system, refer to Wheels/Vehicle Underbody Component Views.

The hydraulic unit with the attached EBCM is located between the surge tank and the fire wall on the left side of the vehicle.

The basic hydraulic unit configuration consists of hydraulic check valves, 2 solenoid valves for each wheel, a hydraulic pump, 2 accumulators, and 2 dampers. The hydraulic unit controls hydraulic pressure to the front calipers and the rear wheel cylinders by modulating hydraulic pressure to prevent wheel lockup.

### Base Braking Mode

#### Hydraulic Diagram

(1) | Master Cylinder
(2) | Orifice
(3) | Damper
(4) | Positive Displacement Pump
(5) | Accumulator
(6) | Inlet Valve
(7) | Right Rear Drum
(8) | Outlet Valve
(9) | Outlet Valve
(10) | Left Front Caliper
(11) | Inlet Valve
(12) | Electric Motor
(13) | Inlet Valve
(14) | Right Front Caliper
(15) | Outlet Valve
(16) | Outlet Valve
(17) | Left Rear Drum
(18) | Check Valve
(19) | Inlet Valve
(20) | Accumulator
(21) | Positive Displacement Pump
(22) | Damper
(23) | Orifice

The baseline braking mode of the MGH-25 antilock brake system (ABS) used in this vehicle is a diagonal split system. In this system, 1 master cylinder circuit supplies pressure to the right front and the left rear brakes. The other circuit supplies pressure to the left front and the right rear brakes. All valves in the hydraulic modulator are in their normal, non-energized positions as shown in the drawings found the hydraulic diagram.

### Antilock Braking Mode - Apply

(1) | Master Cylinder
(2) | Orifice
(3) | Damper
(4) | Positive Displacement Pump
(5) | Accumulator
(6) | Inlet Valve
(7) | Right Rear Drum
(8) | Outlet Valve
(9) | Outlet Valve
(10) | Left Front Caliper
(11) | Inlet Valve
(12) | Electric Motor
(13) | Inlet Valve
(14) | Right Front Caliper
(15) | Outlet Valve
(16) | Outlet Valve
(17) | Left Rear Drum
(18) | Check Valve
(19) | Inlet Valve
(20) | Accumulator
(21) | Positive Displacement Pump
(22) | Damper
(23) | Orifice

If during the pressure hold or pressure decrease mode the electronic brake control module (EBCM) senses that wheel slip has reduced, the EBCM will increase the pressure to the affected wheels by applying master cylinder pressure. The inlet valve is opened and the outlet valve is closed, now base brake master cylinder pressure can be applied to the wheel.

### Antilock Braking Mode - Hold

(1) | Master Cylinder
(2) | Orifice
(3) | Damper
(4) | Positive Displacement Pump
(5) | Accumulator
(6) | Inlet Valve
(7) | Right Rear Drum
(8) | Outlet Valve
(9) | Outlet Valve
(10) | Left Front Caliper
(11) | Inlet Valve
(12) | Electric Motor
(13) | Inlet Valve
(14) | Right Front Caliper
(15) | Outlet Valve
(16) | Outlet Valve
(17) | Left Rear Drum
(18) | Check Valve
(19) | Inlet Valve
(20) | Accumulator
(21) | Positive Displacement Pump
(22) | Damper
(23) | Orifice

When the electronic brake control module (EBCM) senses the wheel slip, the EBCM closes the inlet valve and keeps the outlet valve closed in the brake pressure modulator valve in order to isolate the system. This holds the pressure steady on the brake so that the hydraulic pressure does not increase or decrease.

### Antilock Braking Mode - Release

(1) | Master Cylinder
(2) | Orifice
(3) | Damper
(4) | Positive Displacement Pump
(5) | Accumulator
(6) | Inlet Valve
(7) | Right Rear Drum
(8) | Outlet Valve
(9) | Outlet Valve
(10) | Left Front Caliper
(11) | Inlet Valve
(12) | Electric Motor
(13) | Inlet Valve
(14) | Right Front Caliper
(15) | Outlet Valve
(16) | Outlet Valve
(17) | Left Rear Drum
(18) | Check Valve
(19) | Inlet Valve
(20) | Accumulator
(21) | Positive Displacement Pump
(22) | Damper
(23) | Orifice

If during the pressure hold mode the electronic brake control module (EBCM) still senses wheel slip, the EBCM will decrease the pressure to the affected wheels. The inlet valve is left closed and the outlet valve is opened. The excess fluid/pressure is temporarily stored into an accumulator within the brake pressure modulator valve (BPMV), until the pump can return the fluid to the master cylinder reservoir.

### De-Coupled Dynamic Rear Proportioning (DDRP)

De-coupled dynamic rear proportioning (DDRP) is a proportioning system to maintain vehicle stability during braking. In normal braking condition, equal wheel speed should be maintained for efficient and balanced braking. In hard braking conditions, a vehicle requires relatively less brake force at rear wheel due to vehicle's weight transfer to the front. DDRP maintains desired brake pressure to the rear wheel by using the antilock brake system (ABS) rear inlet and outlet valve in order to provide efficient braking and vehicle stability. In the DDRP system, the power to the rear hold valve solenoid is provided from the ignition. If the following fault conditions are existing, the red brake warning lamp will be illuminated.

• | Two wheel speed sensors inoperative on same axle

• | Rear inlet solenoid inoperative

• | Battery 2, motor input, short to ground

• | Battery 1, electronic brake control module (EBCM) input, open or short to the ground

• | Motor ground open or short to battery

• | EBCM ground open or short to battery

• | Ignition open or short to ground

#### De-Coupled Dynamic Rear Proportioning (DDRP) Failure Modes

Part | Hypothesized Failure | De-Coupled DRP
--- | --- | ---
ABS Warning Lamp | Brake Warning Lamp | D-DRP Status
Sensor RF | Short or Open | ON | -- | Degraded
Sensor LF | Short or Open | ON | -- | Degraded
Sensor RR | Short or Open | ON | -- | Degraded
Sensor LR | Short or Open | ON | -- | Degraded
2 Sensors, Same Axle | Short or Open | ON | ON | Disabled
1 Front and 1 Rear Sensor | Short or Open | ON | -- | Degraded
Motor | Short to Ground - LOW Side | ON | -- | Degraded
Short to Ground - HI Side | ON | -- | Degraded
Short to Battery - LOW Side | ON | -- | Degraded
Short to Battery - HI Side | -- | -- | None
Motor Circuit Open | ON | -- | Degraded
Motor Stalled | ON | -- | Degraded
Front Apply Solenoids | Short or Open | ON | -- | Degraded
Front Release Solenoids | Short or Open | ON | -- | Degraded
Rear Apply Solenoids | Short or Open | ON | -- | Degraded
Rear Release Solenoids | Short or Open | ON | ON | Degraded
System Relay | Open, Unable to Turn ON | ON | -- | Degraded
Shorted On, Unable to Turn OFF | -- | -- | None
Battery 2, Motor | Short to GND | ON | ON | Degraded
Open | -- | -- | Low Voltage
Ground, Motor | Open or Short to Batt | ON | -- | Enabled
Battery 1, EBCM, Solenoids | Open or Short to GND | ON | ON | Disabled
Ground, EBCM, Solenoids | Open or Short to Batt | ON | ON | Disabled
Ignition | Open or Short to GND | ON | ON | Disabled
Brake Switch | Not Applicable | ON | -- | Enabled
Serial Communication | Open or Short | ON | ON | Enabled

### Electronic Brake Control Module (EBCM)

The electronic brake control module (EBCM) performs the following primary functions in order to provide efficient braking and vehicle stability. In the de-coupled dynamic rear proportioning (DDRP) system, power to the rear hold valve solenoid is provided from the ignition. If the following fault conditions are existing, the red brake warning lamp will be illuminated.

• | Monitor wheel speed sensor inputs.

• | Detect wheel slip tendencies.

• | Control the brake system while in the antilock control mode.

• | Monitor the system for proper electrical operation.

The EBCM continuously checks the speed of each wheel to determine if any wheel is beginning to slip. If any wheel slip tendency is detected, the EBCM commands appropriate valve positions to modulate brake fluid pressure in some or all of the hydraulic circuits to prevent wheel slip and provide optimum braking. The EBCM continues to control pressure in individual hydraulic circuits until a slipping tendency is no longer present. Also the EBCM continuously monitors the ABS for proper operation. If the EBCM detects an error, it can disable the antilock brake system (ABS) function and turn ON the ABS warning lamp in the instrument cluster. The EBCM also controls the display of the ABS DTCs while in diagnostic mode.

### Solenoid Relay

The solenoid relay provides power to the pump motor and solenoids. The switch in the relay is normally open, but is commanded to close during initialization. The relay switch will remain closed for the remainder of the drive cycle as long as no diagnostic trouble codes (DTCs) set which require the switch to open. If a DTC sets which requires the relay to be commanded OFF, battery voltage will be removed from the pump motor and solenoids for the remainder of the current drive cycle and antilock brake system (ABS) cannot function. The relay is an integral part of the electronic brake control module (EBCM) and cannot be serviced separately.

### Wheel Speed Sensors and Rings

A wheel speed sensor is present at each wheel. The sensors transmit wheel speed information to the electronic brake control module (EBCM) by means of a small alternating current (AC) voltage. The signal is transmitted to the EBCM through interface that can cause false or noisy wheel speed sensor input to the EBCM.

### Antilock Brake System (ABS) Warning Lamp

The antilock brake system (ABS) warning lamp is located in the instrument cluster and will illuminate if a malfunction in the ABS is detected by the electronic brake control module (EBCM). The ABS warning lamp informs the driver that a condition exists which results in turning OFF the antilock brake function. If only the ABS warning lamp is ON, normal braking with full power assist is available.

Conditions for the ABS warning lamp to turn ON are as follows:

• | ABS malfunction detected--As previously described, the ABS warning lamp turns ON when a problem has been found in the ABS.

• | Instrument panel cluster bulb check--When the ignition is turned to ON, the ABS warning lamp will turn ON for approximately 3 seconds and then turn OFF.

### Brake Warning Lamp

The red brake warning lamp is in the instrument cluster and will illuminate to warn the driver of abnormal conditions in the brake system which may result in reduced braking ability. The lamp will illuminate when the parking brake is applied or not fully released, or if the brake fluid level switch is closed. Closed is when the brake fluid is low in the master cylinder reservoir. When the brake fluid level switch is closed, low condition, a brake warning lamp will stay illuminated until the condition has been repaired. Also some failure modes in MGH-25 system will illuminate the lamp to let the driver know de-coupled dynamic rear proportioning (DDRP) is disabled.

### Traction Control System (TCS)

When drive wheel slip is noted while the brake is not applied, the electronic brake control module (EBCM) will enter traction control mode.

For the North American system, the EBCM requests the engine control module (ECM) to reduce the amount of torque to the drive wheels via the CAN communication circuit. The ECM reduces torque to the drive wheels by retarding spark timing and turning off fuel injectors. The ECM reports the amount of torque delivered to the drive wheels via the delivered torque signal circuit.

If the engine torque reduction does not eliminate drive wheel slip, the EBCM will actively apply the drive wheel brakes only.

For non North American application, traction control is controlled by actively applying the drive wheel brakes only.

During traction control braking, both applications, hydraulic pressure in each drive wheel circuit is controlled to prevent the drive wheels from slipping. The master cylinder isolation valve closes in order to isolate the master cylinder from the rest of the hydraulic system. The prime valve then opens in order to allow the pump to accumulate brake fluid in order to build hydraulic pressure for braking. The drive wheel inlet and outlet solenoid valves then open and close in order to perform the following functions:

• | Pressure hold

• | Pressure increase

• | Pressure decrease

### Traction Control System Indicators

#### TCS Warning Lamp

The electronic brake control module (EBCM) illuminates the TCS Warning indicator when the EBCM detects a malfunction in the traction control system (TCS). The EBCM supplies a ground signal to the instrument panel (I/P) cluster to illuminate the TCS Warning lamp.

The TCS Warning lamp indicator illuminates under the following conditions:

• | There is a malfunction in the TCS.

• | The TCS has been cancelled by pressing the TCS ON/OFF switch located in the center console.

• | When the ignition is first turned ON, the lamp will illuminate for 3 seconds (bulb test).

#### TCS Active Lamp

The TCS Active lamp illuminates when the ignition is first turned ON for 3 seconds along with the ABS lamp, and then both lamps will turn OFF.

The TCS Active lamp will blink when the traction control system (TCS) is operating. When the electronic brake control module (EBCM) detects a wheel spin condition, the EBCM will activate the TCS and blink the TCS Active lamp as long as the wheel slip event is taking place. Once the wheel slip event is no longer detected, the TCS Active lamp will stop blinking.

The TCS Active indicator will illuminate when the EBCM detects a traction control event. The EBCM supplies a ground signal to the instrument panel (I/P) cluster to illuminate the TCS Active lamp.