General
The control module has a built-in diagnostics system (Volvo on-board diagnostic (OBD) system), which monitors input and output signals continuously. Information about system performance can be obtained using the Volvo Scan Tool (ST) connected to the data link connector (DLC).
Miscellaneous
The control module also stores a code indicating the most recent cause of cruise control disengagement. This code is stored in control module memory only as long as the ignition is on.
This test mode displays the last reason the cruise control was disengaged.
This test mode can be used when the cruise control has been disengaged even though the driver has not activated any of the system's components. The code stored will only remain in the memory until the ignition is turned off or the next time the cruise control is disengaged.
Note that the code is not identified as a diagnostic trouble code (DTC) because a code is stored even when the system is disengaged normally, for example when braking.
Note. If the engine is turned off after a test drive the response code 2-1-4 will always be posted when the ignition is turned on even if there is no actual fault.
The following reasons for cruise control disengagement give these codes
- safety disengagement
- gear selector in P or N
- selector switch is set to OFF
- brake valve activated
- clutch valve activated
- brake light switch activated
- supply voltage too low.
Using the Volvo Scan Tool (ST) it is possible to
- Read off and erase diagnostic trouble codes (DTCs) stored.
- Check input signals to the control module.
- Read off the cause of the last cruise control disengagement.
Activating the Volvo on-board diagnostic (OBD) system
- ignition on
- normal battery voltage.
The cruise control selector switch is located on the turning indicator stalk. To activate cruise control vehicle speed must be above 35 km/h, the switch must be ON and the SET button must be pressed in.
When the system has been engaged vehicle speed can be adjusted up or down by pressing the + or - SET button. Every time the SET button is pressed the vehicle speed setting changes by 1.6 km/h (1 mph). If the control module is switched off (by pressing the brake/clutch pedals, the ON/OFF button or by moving the gear selector from D to N) that latest vehicle speed setting is stored in memory until the ignition is switched off. This vehicle speed can be restored by moving the ON/OFF button to the RESUME position.
Braking
Vehicle speed can always be reduced by braking. Cruise control is automatically disengaged. This also happens when the clutch is depressed.
Acceleration
The car can be accelerated with cruise control engaged. When the accelerator pedal (AP) is released the car returns to its set speed.
Vehicle speed can also be increased by pressing the + button. The car will maintain the same speed it has when the button is released.
Disengaging cruise control
Cruise control is disengaged if one of the following occurs
- Selector switch is set to OFF.
- Vehicle speed drops below 35 km/h (22 mph).
- The brake or clutch pedals are used, activating a control circuit via a pressure switch on the pedal.
- The brake pedal is used, activating another control circuit via the stop (brake) light switch.
- Park/Neutral position (PNP) switch on automatic transmission models. Emergency switch. Activated by the control module if the wheels lock or spin. The system is also disengaged the engine cannot achieve the set vehicle speed.