P1289 - CHT Sensor High Input
It's shown in the upper left of this first drawing.
If you're going solely on this fault code with no further testing, be aware diagnostic fault codes never say to replace a part or that one is bad. They only indicate the circuit or system that needs further diagnosis. This is especially true in temperature sensor circuits. Those have an extremely low failure rate because there is just one component inside them. The only notable exception was Ford had a huge failure rate with their coolant temperature sensors in the early 1990s. Other than that, you're much more likely to find a cut wire, or corroded or stretched connector terminals.
Most temperature circuits get 5.0 volts applied to them by a computer, then the circuit draws that down to typically around 1.5 to 4.0 volts, depending on temperature. When there's a break anywhere in that circuit, the voltage pops back up to 5.0 volts. That is what sets this fault code of voltage "high".
To add to the confusion, the circuit diagram shows a coolant temperature sensor for only the Marauder, but in the labor tables, they do list the cylinder head temperature sensor. You'll have to figure out which one is right.
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Saturday, March 1st, 2025 AT 5:55 PM
