Vacuum Pump Assembly
Vacuum Pump Assembly
The vacuum pump assembly contains three components:
- The vacuum pump.
- The vacuum control valve.
- The vacuum dump valve.
The vacuum pump provides the vacuum for the system while the two valves work in conjunction to allow the pump to increase the vacuum to the pneumatic actuator (increase vehicle speed) or release vacuum from the pneumatic actuator (decrease vehicle speed).
The vacuum control valve opens to allow the vacuum pump to increase the vacuum in the pneumatic actuator to increase vehicle speed. When the vehicle reaches the set speed, the vacuum pump control valve closes to hold vacuum in the pneumatic actuator and the vacuum pump is turned off by the cruise control ECU.
The vacuum dump valve is normally open. When cruise control is active, the cruise control ECU provides voltage to close the vacuum dump valve. If power is lost, (e.g. when the brakes or clutch are applied or cruise control is turned off at the cruise control master switch) the vacuum dump valve will immediately open and cruise control will be deactivated.
The cruise control ECU provides power for all three components within the vacuum pump assembly. The cruise control ECU provides earth control circuits for the vacuum pump and the vacuum control valve. The vacuum dump valve is permanently grounded.
Input/Output
The cruise control ECU provides both power and earth to the components within the vacuum pump assembly. Current draw at the vacuum pump assembly varies depending on components operating.
Vacuum Pump Current Draw:
When cruise is requested, the cruise control ECU provides voltage to the vacuum pump assembly and provides a pulsed earth signal. The pulse period is dependent on the difference between the vehicle set speed and the actual road speed. Removing the earth path switches off the pump.
Several fault codes can be generated:
Fault codes
1 "Output power LOW when HIGH is expected" is flagged when Pin C0239-11 is shorted to earth.
This could be due to an external fault or an internal ECU fault and will be set if pin C0239-11 is LOW for longer than 240 milliseconds, while in cruise mode.
2 "Output power HIGH when LOW is expected" is flagged when Pin C0239-11 is shorted to battery voltage.
This could be due to an external fault or internal ECU fault and will be set if pin C0239-11 is HIGH for longer than 250 milliseconds while not in cruise mode.
3 "Output pump LOW, when High is expected" is flagged when Pin C0239-7 is shorted to earth.
This could be due to an external fault or an internal ECU fault. This fault will be set if pin C0239-11 is HIGH for longer than 7.5 milliseconds while pin C0239-7 is LOW for longer than 2.5 milliseconds while decelerating under control of cruise.
4 "Output pump HIGH, when LOW is expected" is flagged when Pin C0239-7 is shorted to battery voltage.
This could be due to an external fault or an internal ECU fault. This fault will be set if pin C0239-7 is LOW for longer than 7.5 milliseconds of the last 8 pulses when the pump is switched on while accelerating under the control of cruise.
5 Output valve LOW, when HIGH is expected is flagged when Pin C0239-7 is shorted to battery voltage.
This could be due to an external fault or an internal ECU fault and will be set if pin C0239-17 is LOW for longer than 2.5 milliseconds while pin C0239-7 is HIGH for longer than 2.5 milliseconds and pin C0239-11 is also HIGH for longer than 7.5 milliseconds, while decelerating under control of the cruise control ECU.
6 Output valve HIGH, when LOW is expected is flagged when Pin C0239-17 is shorted to battery voltage.
This could be an external fault or an internal ECU fault. The fault will be set if pin C0239-17 remains HIGH for longer than 35 milliseconds after the vacuum control valve is switched on, while accelerating under control of the cruise control ECU.
TestBook can be used to determine the fault codes present as well as the general status of the system.