Programmed ignition system (page 2 of 2)

Camshaft position (CMP) sensor The camshaft position sensor has two functions; the first is to enable the ECM to run a sequential fuelling mode; the second is to measure the actual cam period, this measurement is achieved using teeth on the camshaft to indicate when the valve opens and closes. The CMP sensor is monitored by the ECM on BU and RY wires

Manifold absolute pressure (MAP) sensor The manifold absolute pressure sensor is mounted directly on the inlet manifold and provides the ECM with an accurate representation of the load placed on the engine. This allows the ECM to adjust the quantity of fuel being injected together with the ignition timing, to achieve optimum fuelling of the engine. The MAP sensor achieves this by detecting pressure variations inside the manifold, then converting these variations into graduated electrical signals which are monitored by the ECM on RG and YP wires to determine engine load. Earth supply is on a KB wire.

Engine Coolant Temperature (ECT) Sensor The engine coolant temperature (ECT) sensor is located on the coolant outlet elbow. It is a temperature dependent resistor (thermistor), the voltage output of which varies in inverse proportion to temperature, in that the output increases as temperature decreases or the reverse. The change in resistance is monitored by the ECM on a KG wire and as a result the ECM can adjust the length of injector opening time required. The ECM supplies the coolant temperature sensor with an earth path on a KB wire.

Manifold Heater (Japan only) One side of the manifold heater relay coil receives battery voltage from link 4 in the engine compartment fuse box on an NK wire via the closed contacts of the main relay (providing it is energised). The other side of the relay coil receives a control earth on a BK wire from the ECM which energises the relay causing the contacts to close. This switches battery voltage from link 4 in the engine compartment fuse box on an N wire via the relay contacts to the manifold heater on an NU wire. The heater will commence heating since the other side of it is connected to earth

Throttle position sensor The throttle position (TP) sensor is a potentiometer attached to the throttle housing and is directly coupled to the throttle disc. Closed throttle is detected by the TP sensor which initiates idle speed control via the idle air control valve (IACV).

The TP sensor receives a 5 volt supply from the ECM on a YP wire and is supplied with an earth on a KB wire. The sensor then provides a signal which is proportional to throttle disc position on a YG wire to the ECM.