How to troubleshoot an Arduino sensor failure inside a concrete enclosure?

Likely explanation

The sensor may have stopped working because of physical damage to the wiring, moisture‑induced corrosion, or a software fault in the Arduino sketch.

Confirmed facts

• Concrete can hold moisture and alkaline compounds that accelerate corrosion of exposed conductors.
• A broken wire or short circuit will prevent the sensor from communicating with the MCU.
• If the MCU and power supply are functional, re‑flashing the last known‑good firmware often restores operation.

Diagnostic steps

1. Power down and remove the board (if possible) – Disconnect all power sources and, if the enclosure allows, gently extract the Arduino board to avoid further stress on the concrete.
2. Visual inspection – Look for crushed or abraded wires, water stains, white/green corrosion on terminals, or loose connectors. Note any discoloration or brittle insulation.
3. Continuity testing – With a multimeter set to resistance (Ω), measure each wire pair from sensor to Arduino pin while the circuit is powered off.
   • Expect low resistance (< a few ohms) for signal lines.
   • Expect high resistance (> MΩ) between adjacent conductors (insulation check).
   • Record any open circuit (∞) or short (≈0 Ω) as evidence of physical damage.
4. Isolate the microcontroller – Disconnect the sensor and connect a known‑good test load (e.g., a 220 Ω resistor or LED with resistor) to each I/O pin used by the sensor.
   • Upload the Blink example sketch.
   • Verify the onboard LED blinks at the expected rate; this confirms the MCU, power regulator, and crystal are functional.
5. Firmware verification – Re‑flash the Arduino with the last known‑good firmware version using the IDE’s upload button.
   • If upload succeeds and sensor readings resume, the fault was software‑related.
   • If readings remain absent, keep the firmware unchanged and proceed to hardware verification.
6. Rollback if a test does not help – After each step, reverse the last change before moving on:
   • Re‑connect the original wiring if you inserted a test load.
   • Re‑install the previous firmware if you re‑flashed a different version.
   • Replace the test load with the original sensor.

Missing diagnostic detail

Do you have access to a multimeter capable of measuring resistance and continuity? If not, the continuity test cannot be performed and you would need to rely solely on visual inspection and MCU isolation, which may miss hidden wire breaks.