Cruise Control: Testing and Inspection

The instrument described can no longer be ordered. Instead, a BOB and a multimeter should be used.
1 Connect the test instrument.
2 Set the cruise control switch to OFF and turn the ignition switch to ON.
Check that LEDs 1 3 and 5 light up.


NOTE: LED 5 is most likely to light up when the car is moving.


- If diode 1 does not light up, check the power supply to the electronic unit.
- If diode 3 does not light, check the pedal switches and wiring harnesses for these.
- If diode 5 does not light up, drive the car and check the vehicle speed sensor at the speedometer and the wiring harness for it.
3 Press the brake pedal and check that diode 3 goes out. Release the pedal (diode lights up).
Manual gearbox: Press the brake pedal and check that diode 3 goes out again.
- If there is a fault, check the operation and adjustment of the relevant pedal switch as well as the wiring harness (short to ground).
4 Set the cruise control switch to ON and check that LED 9 lights up.
- If the LED does not light up, check the switch and wiring harness.
5 Press the "SET" button and check that LED 2 lights up when the button is held pressed.
- If LED 2 does not light up, check the switch and wiring harness.
6 Press the switch to position "RES" and check that LED 6 lights up when the button is held pressed.
- If LED 6 does not light up, check the switch and wiring harness.
7 Press the "VALVE" button on the test box and listen for whether the cruise control pump is activated.
- If the pump does not work, check the valve and the wiring harness.
8 Press the "PUMP" button on the test box and listen for whether the pump is working.
- If the pump does not work, check the pump and the wiring harness.
9 Pump and valve can also be checked while driving. If the "PUMP" button is pressed, the throttle opens. When "VALVE" is pressed (or the clutch brake pedal is pressed) throttle opening ceases.
- If this does not happen, check the vacuum system.
If the tests in points 1 to 9 give the correct result, the fault lies in the electronic unit.