Circuit Description

WARNING: This page is about a different car, the 2004 Cadillac SRX. However, it is still accessible from the selected car via links, so may be relevant.

The electronic brake control module (EBCM) and the engine control module (ECM) simultaneously control the traction control. The ECM reduces the amount of torque supplied to the drive wheels by retarding spark timing and selectively turning OFF fuel injectors. The EBCM actively applies the brakes to the front wheels in order to reduce torque.

The EBCM sends a requested torque message via a pulse width modulated (PWM) signal to the ECM. The duty cycle of the signal is used to determine how much engine torque the EBCM is requesting the ECM to deliver. Normal values are between 10-90 percent duty cycle. The signal should be at 90 percent when traction control is not active and at lower values during traction control activations. The ECM supplies a pull up voltage of 12 volts that the EBCM switches to ground to create the signal.

The ECM sends a delivered torque message via a PWM signal to the EBCM. The duty cycle of the signal is used to determine how much engine torque the ECM is delivering. Normal values are between 10-90 percent duty cycle. The signal should be at low values, around 10 percent, at idle and higher values under driving conditions. The EBCM supplies a pull up voltage of 12 volts that the ECM switches to ground to create the signal.

When certain ECM DTCs are set, the ECM will not be able to perform the torque reduction portion of traction control. A serial data message is sent to the EBCM indicating that traction control is not allowed.