Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Description
EBCM and PCM simultaneously control traction control. PCM reduces amount of torque supplied to drive wheels by retarding spark timing and selectively turning off fuel injectors. EBCM actively applies brakes to front wheels in order to reduce torque. EBCM sends a requested torque message via a Pulse Width Modulated (PWM) signal to PCM. Duty cycle of signal is used to determine how much engine torque EBCM is requesting PCM to deliver. Normal values are 10-90 percent duty cycle. Signal should be at 90 percent when traction control is not active and at lower values during traction control activations. PCM supplies a pull up voltage of 5 volts that EBCM switches to ground to create signal. PCM sends a delivered torque message via a Pulse Width Modulated (PWM) signal to EBCM. Duty cycle of signal is used to determine how much engine torque PCM is delivering. Normal values are between 10 and 90 percent duty cycle. Signal should be at low values (around 10 percent) at idle and higher values under driving conditions. EBCM supplies a pull up voltage of 12 volts that PCM switches to ground to create signal. When certain PCM DTCs are set, PCM will not be able to perform torque reduction portion of traction control. A serial data message is sent to EBCM indicating that traction control is not allowed.
DTC C1277 sets when PCM diagnoses requested torque signal circuit and sends a serial data message to EBCM indicating a fault is present.
DTC P1571 sets when PCM detects that requested torque signal is out of valid range or PCM does not receive requested torque signal.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.