Typical Toyota Avensis components

With the engine cover removed, the upper part of the motor becomes accessible,

1 including the fuel injectors, at the top of the unit. The injectors are individually coded (marked on the injectors) and it’s essential that their codes are correctly input to the ECU.

With its wiring connector plug

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detached, fuel injector resistance can be assessed using a quality multimeter. The code for the injector – visible in this photograph – can be seen, marked in white on the top of the component’s body.

Your trusty multimeter can also

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be used for checking the electrical resistance of the glow plugs. As with the fuel injectors, the four glow plugs are readily accessible close to the top of the power unit.

Towards the right-hand side of the engine compartment you will find the highpressure

4 fuel pump. The pump body and its pipework are vulnerable to corrosion; check this aspect and ensure that there are no fuel leaks.

The Mass Absolute Pressure (MAP)

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sensor is located at the inlet/intake manifold. Its job is to monitor the pressure at all times within the manifold, relaying this information to the ECU, which accordingly determines the required fuelling levels.

Not very easy to see, nor to photograph, 6

is the air temperature sensor. In this photograph it is the hexagonal component seen approximately in the centre of the shot, beneath the steel bracket supporting the nearby section of the wiring loom.

The Mass Air Flow (MAF) meter/

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sensor is positioned within the inlet/ intake trunking, and is secured in place by two screws. Its function within the system is to monitor air flow rates and to feed this info to the ECU, to adjust fuelling levels.

Should you ever need to reach it,

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it may help you to know that the starter solenoid is hidden away at the front of the engine compartment, and can be seen here in the centre of the photograph.

The 12V battery is partially obscured

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from above, but not too difficult to reach and deal with. Renewal is helped by the fact that it is a traditional lead-acid type. When renewing, no coding is required for the ECU to work correctly with the new unit.

Close to the fuel filter, on the

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left-hand side of the engine compartment, is the glow plug relay. This relay controls the glow plug system, using data from the temperature sensor on the cylinderhead. (See Fault 2).

The underbonnet fusebox is located on the left-hand side of the engine

11 compartment, and inscriptions on the underside of the fusebox lid show the locations and amperage ratings of the fuses within.

Way down low within the engine

12 compartment, and close to the lefthand end of the cylinderhead, is the Exhaust Gas Recirculation (EGR) valve assembly.

Mounted

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low down on the left-hand side of the engine bay is the high-pressure diesel fuel pump. Helpfully, Toyota has built-in a manual primer button on top of the pump, to help draw through fuel if ever the system had been disturbed/ drained and re-filled.

The turbocharger can be seen

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here in the background. For long turbo life it’s essential that the engine oil is clean at all times. Check all pipework connected to the turbocharger; difficulties will arise if air leaks are present.

At the righthand 15 end of the engine, and hidden beneath the cover shown here, is the cambelt. It’s imperative that the belt is renewed at least as often as recommended by Toyota. Always check water pump condition when renewing the cambelt (see ‘Preparation’ section).

The diagnostic socket is located on 16

the right-hand side of the facia, and when not in use is protected by a black clip-on plastic cover, embossed with the lettering ‘OBD-II’.