Secondary Air Pump (SLP)

Secondary Air Pump (SLP)




The electrically-operated secondary air pump is mounted to the vehicle body. The pump draws out filtered fresh air from the air cleaner housing during the warm-up phase and supplies it to the two secondary air Non-return Valves.

Once the engine has been started, the secondary air pump is supplied with voltage by the ECM via the secondary air pump relay. It remains switched on until the engine has taken in a certain amount of air.

The ON period may be a maximum of 90 seconds and it depends on the following engine operating conditions:

- Coolant temperature (from -10 °C to approximately 60 °C)
- Air temperature (NTC sensor in HFM)
- Engine speed

One non-return valve is mounted on each cylinder head (see also Engine Views).

The non-return valves are opened by the pressure generated from the secondary air pump. The secondary air is led through a pipe to the secondary air ducts (integral in the cylinder heads) for distribution into the exhaust ports.

The non-return valves are sprung closed when the secondary air pump is deactivated. This prevents exhaust vapors, pressure and condensation from flowing back into the secondary air pump.