Final answer:
The input terminal of a 2-wire, coolant temperature sensor in a typical truck diesel engine should show a value close to 5 V-DC, supplied by the ECU and independent of the starting batteries configuration.
Step-by-step explanation:
The input voltage value that should be indicated as the input terminal of a 2-wire, coolant temperature sensor in a typical truck diesel engine is usually close to 5 V-DC. This voltage is provided by the engine control unit (ECU) and is expected to vary proportionally to the engine temperature, which can be determined by the varying resistance of the sensor in response to temperature changes. In the case of a truck diesel engine, which may use two 12-V batteries in parallel for larger current during engine start, the sensor's input voltage itself remains standard at around 5 V-DC to be compatible with the electronics of the ECU.