The Engine Coolant Temperature Sensor (ECT) input to the EMS is a primary input for the calculation strategies and control of fuel delivery and spark timing. The ECT is also used to determine loop status (open/closed) timer requirements (inside the EMS) and to support cooling fan operation. ECT failures can cause excessive rich conditions, increased injector pulse-width and retarded spark timing. The ECT reads the coolant temperature at the intake manifold. When the engine coolant is cold the information given to the ECM causes the fuel mixture to richen. As the coolant temperature gradually increases the voltage signal from the ECT changes signaling the ECM to adjust the fuel mixture accordingly.
The following symptoms can be caused by a faulty Engine Coolant Temperature Sensor or circuit loose connections: