I have a 20005 Volvo V50 T5, and the engine light comes on. When checking the

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engine codes: 1.P0031,P0036,P0030 come up for the Heater low voltage sensor. Replaced them and it blows a fuze and the engine light comes on. Whats going on-checked for any wires shorting out-nothing! could you give me any guidance. Many thanks. My Volvo has 65,000 miles, and engine check light comes on.