Typical Vauxhall Astra components

1

The air mass sensor is located within the intake trunking towards the righthand side of the engine bay. The sensor works by monitoring the rate of air flowing through the system. This info is used by the ECU in determining fuelling requirements.

2

The drive-by-wire system’s throttle body assembly, incorporating the throttle flap that regulates fuel mixture supply in response to driver demands, is positioned in the right-hand rear corner of the underbonnet area.

3

Found near the dipstick is the inlet camshaft’s variable valve timing (VVT) sensor. Each camshaft is equipped with a VVT sensor, responsible for changing the camshaft position by altering the supply of oil pressure to the camshaft depending on engine speed and load.

4

Shown in the centre of this photo is the exhaust camshaft’s VVT sensor, located towards the rear of the engine. As with the inlet camshaft VVT set-up, altering the valve timing enables the engine to run more efficiently with regards power, economy and emissions.

5

This is the mass absolute pressure (MAP) sensor, located rather inaccessibly at the rear of the engine. Its function is to monitor the pressure within the manifold at all times, thus aiding the ECU to work out fuelling levels.

6

Here, we’re highlighting the positions of the two camshaft sensors, found at the left-hand end of the cylinderhead. The sensors for both the inlet and exhaust camshafts read from the rear of their respective camshafts. The sensors are three-wire digital form types and an oscilloscope is necessary for testing them.

7

The coolant temperature sensor is integral with the thermostat housing and advises the ECU with regard to the engine temperature. This enables the ECU to judge and apply fuelling levels for optimum running in all conditions, whether the engine is hot or cold.

8

At the front of the engine is the pre-catalytic converter oxygen/o2/ Lambda sensor, which acts to measure the proportion of oxygen in the exhaust gas. This information is delivered to the ECU which, in turn, calculates and applies optimum fuelling levels.

9

The catalytic converter is hidden behind a shield at the front of the engine and is a vital component in minimising emissions. It’s essential that this is positioned close to the engine, as it relies on heat to function correctly and needs to warm up rapidly to operate.

10

The management system’s ECU is located towards the left-hand side of the engine bay, to the right of the battery. This location can result in troubles due to the ingress of moisture, as well as heat from the engine. A good coating of sealant spray at each service can help prevent water damage.

11

The main fuses, plus the live feeds for the battery and alternator, are normally concealed by a plastic cover, found towards the rear of the battery and just ahead of the coolant reservoir. Make sure that the connections are clean and free from corrosion, and that the cover fits snugly.

12

The battery is located on the left-hand side of the engine bay, just inboard of the left-hand headlamp. A traditional lead acid battery is used in this Astra, so it’s less expensive to renew than the enhanced flooded batteries (EFBS) used in many modern cars.