P2ADC

Code

Generic P — Powertrain

Reductant Tank Temperature Sensor B Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 24 EN: 33 RU: 19

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Causes

Open or high-resistance connection in sensor signal or ground circuit
Short to battery voltage on the sensor signal wire
Failed/rejected reductant tank temperature sensor (thermistor or harnessed sensor)
Corroded, contaminated, or water-damaged connector
Faulty reference supply (module 5 V reference) or module internal fault
Faulty wiring due to chafing, pinched cable, rodent damage, or insulation wear

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Diagnostic trouble code P2ADC stored
Incorrect reductant temperature displayed in scan tool or freeze-frame
Possible reduced SCR dosing or limited emissions control functionality
Inability to perform DEF system diagnostics or inhibited regen function (manufacturer-dependent)

What to check

Retrieve freeze frame and monitor live data for reductant tank temperature B and compare to ambient/other temp sensors
Observe sensor voltage or temperature PID with ignition ON and engine OFF; note any fixed high reading
Inspect connector and wiring for corrosion, bent pins, water intrusion, damage, or loose terminals
Backprobe connector to measure signal voltage, reference (usually ~5 V) and ground
Measure sensor resistance at the sensor (cold) and compare to expected developer specs, or check for open/short
Wiggle test wiring while observing live data for intermittent changes

Signal parameters

Typical sensor signal voltage: approximately 0.1–4.5 V during normal operation (varies by design)
Circuit-high condition: sensor signal >4.5–4.8 V (indicates pull-up to supply or open circuit depending on design)
Expected reference supply to sensor: ~5 V (verify with manufacturer spec)
Thermistor resistance example (manufacturer-specific): at ~20°C often in the kΩ range (e.g., 1.5–10 kΩ); consult service data
If sensor is open, resistance reads OL/infinite; if shorted to battery, signal ~battery voltage (~12 V) or highest ECU-sensed level

Diagnostic algorithm

Read and record all related codes and freeze frame data. Confirm P2ADC is current or intermittent.
With connector connected, use a scan tool to monitor reductant tank temperature B PID and sensor voltage. Note value with ambient temp for plausibility.
Visually inspect sensor, connector, and wiring from sensor to module for corrosion, coolant/DEF contamination, pin damage, or chafing.
Backprobe the sensor connector: verify reference voltage (usually ~5 V) and ground presence. If reference is missing or erratic, trace to the ECM/PCM.
Check signal wire voltage with ignition ON: a fixed high voltage (near reference or supply) suggests open sensor or pull-up; near battery voltage indicates possible short to battery.
Disconnect sensor and measure sensor element resistance across its terminals with a multimeter. Compare to manufacturer specification or check for open circuit. If resistance is out of range, replace sensor.
Perform wiring continuity and short-to-power/short-to-ground checks between the sensor connector and the control module connector with harness disconnected. Repair any opens or shorts.
If wiring and sensor test good, swap with known-good identical sensor (if available) or temporarily substitute to confirm fault.
After repairs, clear codes and perform a drive or operation cycle to confirm the code does not return and that reductant temperature readings are plausible.
If all wiring and sensor tests pass but code persists, consider module diagnostics or reflash per manufacturer procedure.