2005 ford focus zx4 st 2.3L. I've changed cyl head temp sensor, thermostat, fuel pressure sensor! Question = Dear Sir, i have some problems with my car, some time stalling, hesitating, cutting out and some few cases it would shut off, so i've checked most of the sensors till i come to the coolant temp sensor; i've checked the sensor and i've found there's no resistance on it at all (engine is cold, haven't run it for 12 hours; next i did disconnect connectors and with key on.
I've made a test to the wires; pcm side, and i noticed there's no power at all (no 5 volt nor the ground are exists), then i've checked the wires to see if they are shorted wires and they are not and i'vr checked the wires from the sensor connector all the way to the pcm by using a multimeter and wires seems to be good both, so please help me what the problem is and how to resolve it if possible. Thanks in advance. Look forward to reading your answer.
Answer: If you are testing for resistance at the coolant temperature sensor, and the sensor has no resistance, then the sensor is bad. If you are testing the entire circuit from the computer connector to the sensor and back to the computer, with the computer disconnected and there is no resistance, then there is an open in that circuit, or you are not testing the correct wires. If with all connected and there is no 5 volt reference or ground, then the either the PCM is bad or again, you are testing the wrong wires.
The sensor itself has the have resistance in it for the system to work. If the PCM does not know the resistance, then it does not know the coolant temperature and this could be giving you your driving problems. It should also set a code in the PCM with a check engine light on.
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