Haier Washing Machines Temperature sensor error, can I fix this myself?
The first thing to do is to clean the machine following the manufacturer's directions in the owner's manual. I've seen a number of washing machines that generated fault codes because lint or other muck gummed up a sensor; the cleaning process often is enough to take care of the problem. In the U. S., we have a product called CLR (Calcium, Lime and Rust remover) that does a nice job of cleaning out washing machines. I think the primary ingredient is dilute citric acid. Some manufacturers recommend chlorine bleach - go with what is in the manual first.
If the cleaning process doesn't eliminate the error code, yes, you probably still can fix the washer, if you can open it. If you know the model number, you may even be able to obtain a service manual that will tell you what to look for. Warning: unplug the machine before removing any covers. Exposed electrical terminals are a shock hazard if the machine is plugged in.
Some appliances have a wiring diagram attached inside, or on a service sheet stored inside the control panel. If you find it, the wires going to the temperature sensor will be identified by the colors. For example, a YEL/BLK wire is yellow with a black stripe. You can trace these wires to find and identify the temperature sensor.
Once you find the sensor (it will be somewhere in contact with the wash water, probably on or near the tub), inspect the electrical connections at the sensor and at the control unit, and clean up or repair any corroded connections. Check the wiring to make sure it hasn't been pinched between parts and damaged. If the wiring looks good, take the sensor out and remove any muck that is built up on it. Be sure to wipe clean the gasket or o-ring, and any sealing surfaces in contact with the gasket. Re-install, put the machine back together (being careful not to pinch any wires between parts or panels!) and test it.
If you still get the error, you may have to replace either the sensor or the controller.