A sensor circuit may use a defined reference return rather than any convenient metal point. Measuring against an unsuitable reference can change the apparent result and lead to an incorrect diagnosis.
Keep the measurement location
Ask the technician to identify both probe locations and the circuit diagram used. A voltage number without that information is incomplete evidence. Do not add a chassis-ground jumper to a sensor return as an improvised repair.
For an ECU enquiry, include the original measurements, operating state and related sensor symptoms. The specialist should explain whether the observation concerns the signal, supply or reference path. Correct reference selection helps distinguish a genuine abnormality from a result created by the measurement method itself.
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