Hill Descent Control (HDC) Signal: Function
The HDC signal output from the ECM is via pin 29 of connector C0636. The ECM generates a PWM signal that varies in pulse width in accordance with changing throttle angle or engine torque. The throttle angle data is transmitted on pulses 1, 3, 5 and 37. The engine torque data is transmitted on pulses 2,4,6 and 38. The engine and transmission information is transmitted on pulse 39. A synchronizing pulse is transmitted after every 39th pulse.
The HDC signal can fail in the following ways:
- Harness or connector damage.
A HDC signal failure may be evident from the following:
- HDC/ABS warning light on.
- HDC inoperative.
- Audible warning.
Should a malfunction of the HDC signal occur, the following fault codes may be evident and can be retrieved by TestBook/T4. See Fig 1.