Electronic Control Unit (Ecu)
All components of the control system are electrically connected to the ECU. See Fig 1. The ECU is a preprogrammed computer which receives and interprets data from various sensors. It calculates the amount of fuel required by the engine to maintain efficiency with minimum exhaust emissions.
Impulses from the oxygen sensor inform the ECU of oxygen content of exhaust gases and the ECU constantly adjusts the air/fuel ratio by controlling the injector "open" time.
The ECU provides fuel enrichment whenever engine is cranked, regardless of engine temperature. This is activated by a direct electrical connection from the starter circuit to the ECU. On BMW, Porsche 944 and Renault Fuego Turbo models, the ECU also controls ignition timing. The ECU is a sealed unit. No service is required.