Adaptive Speed Control Module (ASCM)

The Adaptive Speed Control Module (ASCM) is attached to a bracket located in the armature of the front bumper, in the centerline of the vehicle.

The ASCM contains a forward looking radar transceiver together with related controlling hardware and software. The HS CAN powertrain systems bus connection allows the ASCM to communicate with other system control modules. Power supplies to the ASCM are from the Extended ignition relay in the Rear Junction Box (RJB) and the ACC relay in the Engine Junction Box (EJB).

The ASCM is active whenever the ignition is on, even if speed control is not engaged, in order to operate the forward alert and Advanced Emergency Brake Assist (AEBA) functions. With the ignition on, the ASCM is powered up but no radar transmissions are emitted until the vehicle is in motion.

The ASCM transmits a radar beam forward of the vehicle and detects the returning signals reflected off other vehicles and objects ahead. The radar beam is electronically scanned at a rate of 20 sweeps/second across a total arc of 20° centered on the longitudinal axis of the vehicle. The radar operates at millimetric wavelengths (76 - 77 GHz) and transmits a frequency modulated continuous wave signal at a relatively low power level (no high power pulses). The control module detects the range, relative velocity and angle of objects within the scanned arc for up to a distance of approximately 130 meters (426.5 feet).

The ASCM compares vehicle speed data from the ABS control module with the relative speed of an external object as detected by the radar to ascertain whether the object is stationary or not. If tires are fitted which are different in diameter from those specified for the vehicle, the vehicle speed, calculated by the ABS module, will not be the true road speed. This situation may cause stationary objects to be falsely identified as moving vehicles and result in automatic deceleration on a clear road.

The ASCM continuously monitors both moving vehicles and stationary objects to determine if it can 'see' normally. If the control module can detect only a few objects, because it is physically blocked (for example by an accumulation of snow or mud on the upper grille, fitting of a vehicle front protector or metallized badges), or there are few roadside objects or other vehicles in the area, it may determine that it is blocked. The ASCM then inhibits adaptive speed control and records a DTC (Diagnostic Trouble Code). The system will reset after the ignition is cycled. In this case the ASCM is not faulty and should not be replaced.

A vertically misaligned ASCM (caused by minor front collision) can detect only a few objects because it is physically misaligned, it may determine that it is blocked and generates a DTC. In this case, the ASCM should not be replaced; it must be mechanically vertically aligned.

Refer to: SPEED CONTROL SENSOR ADJUSTMENT  .

If the ASCM is replaced in service it must be mechanically aligned vertically. Horizontal alignment is achieved by putting the control module into service mode using approved Jaguar diagnostic equipment. The vehicle then needs to be driven for a short period while the control module calibrates itself. Calibration is complete when the follow mode warning indicator in the instrument cluster stops flashing.

Refer to: SPEED CONTROL SENSOR ADJUSTMENT  .