Cruise control – circuit operation

CRUISE CONTROL – CIRCUIT OPERATION

SET/ACCEL

To set a cruise speed, the Cruise Control Switch (X115) must be on and vehicle speed must exceed 28 mph (45 km/h). When the SET/ACCEL Switch is depressed under these conditions, the Inverter/Converter (Z249) is suppplied with a ground signal. This signal is transmitted via the OY wire to the Engine Control Module (ECM) (Z132) causing the vehicle to accelerate. When the SET/ACCEL Switch is released, the signal is removed signalling the Engine Control Module (ECM) (Z132) to set the speed.

RES

When the RES Switch is depressed, a signal is applied to the ECM (Z132) and the vehicle will return to the previously set speed.

Speed Input

The BeCM (Z238) receives the vehicle speed signal from the Anti-lock Brake System ECU (Z108). The BeCM (Z238) then provides the vehicle speed signal to the Engine Control Module (ECM) (Z132). This signal is a pulsing voltage and its frequency changes with the vehicle speed.

System Disable

The cruise control system can be disabled in two ways: 1. The Cruise Control Switch (X115) is put in the 0 position, causing the BeCM (Z238) to remove power from the Engine Control Module (ECM) (Z132) and erasing the set speed memory. 2. The Voltage applied via the Inverter/Converter (Z249) to the Engine Control Module (ECM) (Z132) terminal 20 is interrupted, causing the Engine Control Module (ECM) (Z132) to disengage the system. This voltage path is interrupted when : The brake pedal is depressed. The Engine Con
trol Module (ECM) (Z132) has two Stop Lamp Switch (X168) inputs, each of opposite polarity. The ECM (Z132) compares the polarity states to determine when the brake pedal has been depressed. The vehicle speed does not exceed 28mph (45
km/h). The vehicle is not in a forward gear (P, R, or N)
(Automatic Transmission).

The clutch pedal is depressed (Manual Trans
mission).

The BeCM (Z238), which monitors these signals, will then remove power from C255/Pin 18.