Boost Pressure (BP) Sensor (Engine management system - EDC)

If the MAF sensor fails the ECM implements a back up strategy, which is based on engine speed. In the event of a MAF sensor signal failure any of the following symptoms may be observed: l Difficult starting. l Engine stalls after starting. l Delayed engine response. l Emissions control inoperative. l Idle speed control inoperative. l Reduced engine performance.

Should the IAT sensor fail the ECM defaults to an assumed air temperature of -5 °C (23 °F).

In the event of an IAT sensor signal failure any of the following symptoms may be observed: l Over fuelling resulting in black smoke. l Idle speed control inoperative.

Boost Pressure (BP) Sensor

The BP sensor is located on the front side of the intake manifold and has a three pin connector. It provides a voltage signal relative to intake manifold pressure to the ECM. The BP sensor works on the piezo ceramic crystal principal. Piezo ceramic crystals are pressure sensitive and, in the BP sensor, oscillate at a rate dependent on air pressure. The BP sensor produces a voltage between 0 and 5 volts proportional to the pressure level of the air in the intake manifold. A reading of 0 volts indicates low pressure and a reading of 5 volts indicates high pressure. The ECM uses the signal from the BP sensor for the following functions: l To maintain manifold boost pressure. l To reduce exhaust smoke emissions while driving at high altitude. l Control of the EGR system. l Control of the vacuum control module

ECM supplies the BP sensor with a 5 volt power supply. The output from the BP sensor is measured at the ECM. The earth path is supplied via the ECM.

In the event of a BP sensor signal failure any of the following symptoms may be observed: l Altitude compensation inoperative (engine will produce black smoke). l Active boost control inoperative. l The ECM assumes a default pressure of 0.9 bar (13 lbf/in²).

Engine Coolant Temperature (ECT) Sensor

The ECT sensor is located in the engine block at the front of the engine. It provides the ECM with engine coolant temperature information. The ECM uses this ECT information for the following functions: l Fuelling calculations. l Temperature gauge. l To limit engine operation if coolant temperature is too high. l Cooling fan operation. l Glow plug operating time.