A probe is part of the measurement circuit. If connecting it changes the symptom, the result may be revealing a sensitive circuit or a test arrangement that is loading the signal.

What to check next

Record exactly how the behaviour changes and review probe impedance, grounding and access method. Compare with the approved test setup before drawing a conclusion. An intermittent connector that moves during probing is another possibility, so preserve the original condition as far as practical.

Useful information for an enquiry

Include the instrument, probe type and whether the fault clears only while connected.

A temporarily improved reading is not a repair. Avoid leaving improvised probe connections installed to keep the vehicle functioning.

Speak to AXION

For complex vehicle-electronics diagnostics, send your vehicle details and fault report. Workshop assessment is in Didcot, Oxfordshire. Suitable postal or remote work is confirmed before booking.

Technical background from Pico Technology. The referenced design explains the principle; the vehicle-specific procedure determines the repair.