Rick's Free Auto Repair Advice

Posts Tagged: ECT

P0125 Fix

P0125 Fix Insufficient Coolant Temperature For Closed Loop Fuel Control You need to determine whether the engine coolant temperature sensor is telling the truth and the engine really isn’t coming up to operating temperature, or whether the sensor is bad. Many DIYers rush to replace the sensor. And yes, they do go bad. But not nearly as often as the thermostat. So start your diagnostics by checking coolant level. If it’s low, fill it. Then, using an infra-red thermometer, check the temp around the thermostat housing. At operating temperature, it … Read More

Test engine coolant temperature sensor ECT

How to test an engine coolant temperature sensor An engine coolant temperature sensor is usually a variable resistor that changes resistance and thus voltage as the coolant temperature changes. To test the sensor, you can remove the electrical connector and check the resistance value of the sensor and compare it to specs. If it’s way off, replace it. But if it’s close, you really need to perform a voltage test, since it’s far more accurate than an ohm test. To test the voltage, you’ll need to either back probe the … Read More

Hard starting and stalling, bad gas mileage

What causes Hard starting, stalling, and  poor gas mileage There are many things that can cause hard starting and stalling poor gas mileage, but the key to solving this particular puzzle is the clue about poor gas mileage. One inexpensive sensor can be the cause of all these problems—the engine coolant temperature sensor (ECT). When you turn the key, the computer takes a quick look at the ambient air temperature and the ECT. By comparing the two temperature readings the computer knows whether the engine is cold or at operating … Read More


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