MANIFOLDS AND EXHAUST SYSTEM – Td6, DESCRIPTION AND OPERATION, Description. If the boost control solenoid valve fails, the vanes remain in the fully open position. In the event of solenoid valve failure, the following symptom will be observed: l The engine will produce less torque at lower engine speeds. The solenoid coil has a resistance of 15.4 ± 7.0 Ω at CF. The solenoid valve can be activated using TestBook/ T4 for test and diagnostic purposes. Engine Coolant Temperature (ECT) Sensor The ECT sensor is located on the LH side of the cylinder head, between the two rear air inlet ports. The ECT sensor provides the ECM and the instrument pack with engine coolant temperature status.
ENGINE MANAGEMENT SYSTEM – TD6 DESCRIPTION AND OPERATION The ECM uses the temperature information for the following functions: l Fuelling calculations l Limit engine operation if engine coolant temperature becomes too high l Cooling fan operation l Glow plug activation time. The instrument pack uses the temperature information for the following functions: l Temperature gauge operation. The engine coolant temperature signal is also transmitted on the CAN by the instrument pack for use by other systems. The ECM ECT sensor circuit consists of an internal voltage divider circuit which incorporates an NTC thermistor. As the coolant temperature rises the resistance through the sensor decreases and visa versa. The output from the sensor is the change in voltage as the thermistor allows more current to pass to earth relative to the temperature of the coolant. The ECM compares the signal voltage to stored values and adjusts fuel delivery to ensure optimum driveability at all times. The engine will require more fuel when it is cold to overcome fuel condensing on the cold metal surfaces inside the combustion chamber. To achieve a richer air/fuel ratio, the ECM extends the injector opening time. As the engine warms up the air/fuel ratio is leaned off. The input to the sensor is a V reference voltage supplied from the voltage divider circuit within the ECM. The ground from the sensor is also connected to the ECM which measures the returned current and calculates a resistance figure for the sensor which relates to the coolant temperature. The following table shows engine coolant temperature values and the corresponding sensor resistance values. If the ECT sensor fails, the following symptoms maybe observed: l Difficult cold start l Difficult hot start l Engine performance compromised l Temperature gauge inoperative or inaccurate reading. In the event of ECT sensor signal failure, the ECM applies a default value of CF) coolant temperature for fuelling purposes. The ECM will also permanently operate the cooling fan at all times when the ignition is switched onto protect the engine from overheating.