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Generic P — Powertrain

Reductant Tank Temperature Sensor B Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 23 EN: 31 RU: 25

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Temperature sensor element failed (open or shorted)
Short to ground in sensor signal or ground circuit
Damaged, corroded, or loose connector at sensor or ECM
Broken or shorted wiring harness (pinched, chafed, water intrusion)
Extreme low ambient temperature or frozen reductant; sensor reading legitimately very low
ECM/PCM fault or internal input circuitry failure

Read freeze-frame and live data with a scan tool: note reductant tank temperature B value and related reductant system codes
Perform a visual inspection of the sensor, connector, and harness for corrosion, damage, or moisture
Backprobe the sensor connector to verify reference voltage, signal voltage, and ground with ignition on
Measure resistance of the sensor (if removable) and compare change vs. temperature; verify it changes smoothly as warmed/cooled
Check for continuity to ECM and for shorts to ground or battery using a multimeter
Inspect reductant tank for signs of contamination, flooding, or ice that could affect the sensor

Sensor type: typically a thermistor (NTC or PTC) that changes resistance with temperature
Expected behavior: resistance changes with temperature (NTC: resistance decreases as temperature rises); signal voltage moves accordingly
Typical signal interface: ECM provides a reference and reads sensor voltage; expected signal range varies by vehicle (commonly within ~0.1–4.9 V), consult OEM service data for exact values
A persistently low signal voltage (near 0 V) usually indicates a short to ground or failed sensor
A fixed/open signal (no change with temperature) indicates open circuit, corrosion, or failed sensor

Retrieve freeze-frame and pending history using a scan tool. Note any related reductant/DEF system codes.
Visually inspect sensor connector and harness for corrosion, bent pins, water intrusion, damage, or loose terminals. Repair as necessary.
With connector plugged in, backprobe the sensor connector and verify reference voltage and ground presence per OEM data. If no reference/ground, suspect wiring or ECM.
Measure the sensor signal voltage with ignition on and engine off. Compare to expected range from service manual. Wiggle harness to check for intermittent faults.
If possible, disconnect sensor and measure sensor resistance across its terminals. Warm or cool the sensor (hot water/ice as safe) and confirm resistance changes smoothly. Replace sensor if resistance is out of spec or does not change.
Check continuity between sensor signal and ECM input; check for short to ground by measuring resistance from signal wire to chassis ground with power removed.
Repair any damaged wiring, clean/replace corroded connectors, and secure harness against chafing. Replace sensor if failed.
After repairs, clear codes and perform a test drive or required drive cycle. Re-scan to confirm code does not return and that reductant system operates normally.
If wiring and sensor check good but fault persists, consider ECM input circuit fault and consult OEM procedures for module testing or replacement.