Technical questions at the CSDD exam

A winter tyre is recognised by the 3PMSF “mountain and snowflake” marking on the sidewall — since 1 October 2024 only such a tyre counts as a winter tyre in Latvia; the older “M+S” mark is no longer enough. Winter tyres are mandatory from 1 December to 1 March for vehicles up to 3.5 t. Tread depth in that period must be at least 4 mm, and at least 1.6 mm for a car the rest of the year. Studded tyres are banned from 1 May to 1 October. A summer tyre hardens in the cold and loses grip, so the temperature matters as much as the date.

What the examiner is checking: The examiner expects you to point at the marking on the sidewall, not just name the season.

Pressure is measured with a gauge and only on cold tyres: after driving the air warms up and the reading is higher than the real value. The required pressure is set by the car maker — it is on the sticker in the driver's door opening, sometimes on the fuel flap or in the manual, and differs for the front and rear axle and for a fully loaded car. By eye you can only spot a badly deflated tyre. Too little pressure raises fuel use and wears the shoulders, makes the car feel floaty and the tyre easier to damage in a pothole; if only one tyre is low, braking can pull the car sideways. Too much pressure wears the centre of the tread, reduces comfort and shrinks the contact patch.

What the examiner is checking: Do not quote a single “correct” figure: the car sets the pressure, not an average value.

Safety first: stop as far from the carriageway as possible on firm level ground, switch on the hazard lights, put on a reflective vest and set out the warning triangle. Then switch off the engine, apply the parking brake and engage a gear (or “P”), and chock the opposite wheel. Loosen the bolts while the wheel is still on the ground; raise the car with the jack only at the designated jacking point; change the wheel; start the bolts crosswise; lower the car and only then tighten fully. Before fitting, clean rust and dirt off the mounting face, as they can let the bolts work loose; start the first two bolts by hand, opposite each other. Never get under a raised car, and while it is on the jack do not start the engine or leave anyone inside. Finally collect the tools and triangle, check the pressure as soon as you can and re-check the bolt torque after 100 km.

The coolant sits in the expansion tank under the bonnet — the tank is semi-transparent and marked “MIN” and “MAX”. Check the level visually on a cold engine and on level ground: it must be between the marks. Never open a hot system — it is pressurised and the steam can scald you. To top up, undo the cap slowly to release the pressure and add the same fluid that is already in the system; in an emergency distilled water will do, but the antifreeze strength must be checked afterwards. A level that keeps dropping means a leak, and that is a job for the garage.

The car must stand level with the engine off and cool (or a few minutes after running, so the oil drains back). Pull out the dipstick — its handle is usually yellow or orange, sometimes marked “Engine Oil” — wipe it, push it fully back in and pull it out again. The oil film must be between the “MIN” and “MAX” marks (the gap is usually about 1–1.5 litres). Some newer cars have no dipstick and show the level on the trip computer. Top up a little at a time with the same oil and check again: overfilling is as harmful as running low.

The washer reservoir cap carries a windscreen-and-jet symbol; check the level by eye — many cars warn about a low level on the dashboard. In winter use winter fluid: summer fluid freezes and can split the tank. Switch the wipers on with the stalk by the steering wheel, with the ignition on. The stalk positions give a single wipe, an intermittent mode and two continuous speeds; pulling the stalk towards you runs the washer together with the wipers, pushing it away works the rear wiper or washer if fitted.

The hazard button with the red triangle is on the dashboard and works even with the ignition off. On most European cars the light switch is to the left of the steering wheel or on the indicator stalk; the usual positions are off, side lights, dipped beam, with fog lights separate. Main beam goes on by pushing the stalk away, a flash by pulling it towards you. In Latvia daytime running lights or dipped beam must be on around the clock, all year. The dashboard tell-tale confirms what is switched on.

The dashboard normally has a speedometer, rev counter, fuel and coolant temperature gauges and an odometer. Read the warning lights like traffic lights: red means do not drive on — stop and find the cause (oil pressure, brakes, overheating, charging); amber means you may drive, but only as far as the garage (ABS, engine fault, tyre pressure); blue and green only tell you a function is on, such as main beam or an indicator. When you switch on the ignition the lights come on briefly for a self-test and then go out.

With the engine off, press the brake pedal several times: it must firm up and stay high. If the pedal slowly sinks to the floor, the system has a leak or air in it. When you start the engine the pedal drops slightly — that is the vacuum servo working and it is normal. Also check the brake fluid in the translucent reservoir between “MIN” and “MAX”, and the parking brake, which must hold the car on a slope. On the move braking must be even, without pulling to one side, knocking or squealing. An “ABS” light means the brakes work but without ABS, so drive to a garage.

Cruise control holds a set speed so the driver need not keep a foot on the throttle: on a long monotonous road it reduces fatigue, helps avoid speeding and saves fuel. Plain cruise control cannot see distance — the speed stays the same even if the car ahead brakes. Adaptive cruise uses radar or a camera to keep a chosen gap, slowing and accelerating on its own. The risks are shared: attention fades, reaction time grows, and on a wet or icy road or in dense traffic the system does not take responsibility off the driver. Pressing the brake pedal switches cruise control off.

Parking sensors use ultrasound to measure the distance to an obstacle and turn it into sound: the closer you get, the faster the beeps, and a continuous tone means stop. Many cars also show the distance on screen as coloured bars or with a camera image. The sensors work at low speed and are an aid, not a replacement: they can miss a low kerb, a narrow post, or be blinded by snow or dirt on the sensors themselves. So even with them you must look around and in the mirrors when reversing.

Radar, lidar or a camera constantly measures the distance and speed difference to the object ahead. If a collision becomes likely, the system warns first — a red symbol on the dash, a sound, sometimes a vibration in the wheel or belt. If the driver does not react, autonomous emergency braking (AEB) brakes by itself to avoid the impact or at least cut the speed and the damage. The system is not absolute: fog, rain, snow, a dirty camera and a very large speed difference all limit it, and it never replaces a safe gap and attention.

Lane assist watches the road markings with a camera and warns if the car starts to leave its lane without an indicator on; the active version nudges the steering back. It only works where the markings are clearly visible, so snow, a worn line or heavy rain switch it off. Blind-spot sensors use radar to watch the adjacent lanes and the area behind: if a vehicle is there, a light comes on in that door mirror, and with the indicator on it flashes or adds a sound. Blind-spot sensors often fail to pick up a bicycle or a motorcycle — in town that is a danger of its own. Neither system replaces turning your head before changing lanes.