Hill Descent Control (HDC) signal (Engine management system - V8)

Should a malfunction of the rough road signal occur, the following fault codes may be evident and can be retrieved by TestBook:

Hill Descent Control (HDC) signal

The ECM transmits throttle angle, engine torque, engine identification (Td5 or V8), and transmission type (automatic or manual) data to the SLABS ECU to support the Hill Descent Control system. The information is transmitted via a 0 – 12V pulse width modulated (PWM) signal at a frequency of 179.27 Hz.

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 synchronising pulse is transmitted after every 39th pulse.

The HDC signal can fail in the following ways: l Harness or connector damage

A HDC signal failure may be evident from the following: l HDC / ABS warning light on l HDC inoperative l Audible warning

Should a malfunction of the HDC signal occur, the following fault codes may be evident and can be retrieved by TestBook:

Low fuel level signal

When the fuel level in the fuel tank becomes low enough to illuminate the low fuel level warning lamp in the instrument cluster, the instrument cluster generates a low fuel level signal. If the low fuel level signal is present during the ECM misfire detection function the ECM can use it to check for a 'false misfire'.

Conditions The fuel sender generates the low fuel level signal when the fuel sender resistance is greater than 158 ± 8 ohms.