Which sequence best represents a basic troubleshooting flow for a non-responsive sensor?

• A. Replace the sensor and hope for best
• B. Disconnect the power and leave it for an hour
• C. Increase supply voltage beyond rating
• D. Check power presence, verify sensor output with a known-good indicator, inspect wiring/connectors, test for shorts/opens, swap with a known-good sensor or input module, verify controller expectations

Answer: (D)

A methodical diagnostic flow is used to locate a non-responsive sensor by first confirming basic power and signal readiness, then verifying the actual output with a known-good reference, and finally isolating the fault through wiring checks, short/open tests, and comparisons with a known-good sensor or input module. Start by ensuring power is present to the sensor; without power, nothing will respond. Next, test the sensor’s output with a known-good indicator (like a test tool or reference meter) to confirm that the sensor is producing a signal rather than the issue being on the controller side. Then inspect wiring and connectors for any damage, looseness, or corrosion, since physical faults frequently suppress or distort signals. Check for shorts to supply or opens in the circuit, which can mask or distort readings. Swapping in a known-good sensor or input module helps determine whether the problem follows the sensor or the controller/input channel. Finally, verify that the controller’s input expectations (signal type, range, polarity, scaling, and wiring conventions) match what the sensor provides and that the controller is configured correctly to read that signal. This sequence quickly narrows down the root cause and avoids unnecessary replacements or unsafe changes.

Other options lack this systematic approach, such as replacing the sensor without diagnosis, or actions like disconnecting power for a long period or pushing voltage beyond rating, which can mask issues or cause damage.