Typical BMW 1-Series components
7 Found just to the rear of the electronic throttle body is the mass absolute pressure (MAP) sensor. This sends information on the pressure within the manifold to the ECU, which uses the figures to help calculate correct fuelling. 8 Very well-hidden, the oil pressure switch (you can just see its electrical cables) illuminates if the oil pressure drops too low. However, by the time the red warning lamp illuminates, damage may already have been done (see Preparation). 9 The water-cooled oil filter housing is very accessible, being positioned at the top of the engine. Always use high-quality oil filters; a dodgy filter may restrict engine oil flow and can cause the oil pressure warning lamp to flash. 10 The L-shaped component visible here just behind the engine bay’s vertical rear bulkhead panel is the ambient temperature sensor – important in a car with automatic temperature control. It monitors external temperatures to set the optimal interior temperature. 11 The bonnet position sensor detects whether the bonnet is fully shut. If not, a warning lamp on the dash will illuminate. Note: on newer BMWS, it is necessary to pull the bonnet handle twice to open the bonnet – this catches out a lot of people. 12 Visible just left of the centre of this photograph is the variable valve timing solenoid for BMW’S sophisticated VANOS valve timing system. The solenoid employs engine oil pressure to activate the mechanical parts of the system to vary the timing.
14 Positioned on the driver’s heelboard, but almost completely hidden by the accelerator pedal, is the throttle position sensor. This instantly supplies precise information on the accelerator position to the ECU, which adjusts engine speed accordingly.
17 This screenshot of the Snap-on Verus Pro diagnostic tool shows the fault code readout from the engine ECU. There are multiple ECUS around the vehicle and the Verus Pro can very effectively communicate with them all. 15 Powering all electrical systems is the battery, with an extra (and costly) complication in the form of a fuseboard assembly. If any of the fuses blow, a complete assembly is required (around £250 new, but secondhand units can be found, although they will need to be coded to the car). Don’t allow the battery to become discharged or else…
18 The Verus Pro tool shows function options available to the operator, relating to the immobiliser system. Here it shows if the key is being read and indicates the state of the immobiliser (ie, active or not), which is useful in a non-start situation. 16 …when the ignition key is pushed into the slot, nothing will happen. Another problem in this area can be the lock/immobiliser assembly. When you push the key, you should hear a clunk to show the ignition lock has been released. 19 Another handy function of the Verus Pro tool when used with this BMW model is that it can tell the operator about the quality/condition of the engine oil. In this case, we had just changed the oil and filter, so the quality level was 99%. The Verus Pro can also advise the operator regarding wear levels on the front and rear brake pads (the system should be reset when the pads are renewed). With this 1-Series, the complete service history can be recorded in the maintenance book and by computer.