Back Up Facility

Back Up Facility

In the event of certain input failures the ECM will implement a back-up air fuel ratio to maintain driveability. A back-up value is provided for the coolant sensor, inlet air sensor and manifold absolute pressure sensor.

Back Up Values:

Coolant sensor 60C Inlet air sensor 35C

Manifold absolute pressure. The ECM implements air fuel ratio relating to engine speed and throttle position.

Throttle position sensor The throttle position sensor is a potential divider which is connected to the throttle disc spindle. The ECM provides a 5 volts supply to the throttle position sensor on the Y/P wire and an earth return on the K/B wire. A third wire, Y/G is connected to the position sensor and transmits a voltage output signal back to the ECM indicating the rate of throttle opening.

Inlet air temperature sensor The inlet air temperature (IAT) sensor is located in the side of the inlet manifold. The IAT sensor is a negative coefficient (NTC) type, which reduces its resistance with increasing temperature. The ECM receives a signal proportional to the temperature of the intake air on the G/B wire, earth is on the K/B wire. This signal is used in conjunction with the signal from the manifold absolute pressure sensor, by the ECM to calculate the volume of oxygen in the air and adjust the quantity of fuel being injected to achieve optimum fuelling of the engine.

Exhaust Emission Control (closed loop) The ECM uses a signal from the oxygen sensor on the S and LG/S wires to control exhaust emissions. This system controls the air/fuel ratio to 14.7:1 at idle and cruise conditions.