Bosch Motronic - Component Datasheet |
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Coolant Temperature Sensor (G62) This device is also known as the Engine Coolant Temperature sensor (or ECT for short). Located on the rear of the cylinder head, G62 provides the ECU with a signal pertaining to the coolant temperature. This is needed to provide adjustments to ignition timing; injection timing during cold or hot starts. It is also used to ensure proper fuel enrichment in the warm-up cycle and cold idle stabilisation. G62 is a negative temperature coefficient (NTC)
thermistor. That means the resistance value decreases with an increase in temperature.
As such, when it fails or is disconnected, one would expect the
ECU to interpret settings for a cold engine. However a little more intelligence
is built into the ECU such that a substitute value is utilised with knowledge
of the intake air temperature measured at G42. This is a good thing as the subsequent rich running (as if the engine was cold) would provide both poor performance and poor fuel economy.
Testing the Engine Coolant Temp sensor (ECT), G62 Using a DMM set for resistance, and the engine
cold at an ambient air temperature of 20 degrees Celsius, expect a value
of approx 2500 ohms across the two pins of G62. The figure below shows the temperature - resistance graph for G62. This is very useful for tests across at a wide range of values. |
Last Updated 11th November 2007