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DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P2046

P2046Reductant Temperature Sensor Circuit Intermittent

P2046 indicates that the powertrain control module has detected an intermittent fault in the reductant temperature sensor circuit, which monitors the temperature of the diesel exhaust fluid (DEF) tank or lines. The circuit's signal momentarily drops out or becomes erratic, rather than failing completely, so the computer cannot reliably trust the sensor reading.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms.
  • Intermittent or erratic DEF temperature gauge readings on vehicles equipped with a display.
  • Possible activation of a limp mode or reduced engine power if the fault persists and the system cannot verify DEF temperature.
  • Difficulty starting the engine in extreme cold if the heater strategy relies on accurate temperature data.
  • Occasional false low-fluid or quality warnings triggered by the unstable signal.

Common causes, most likely first

  1. Chafed, corroded, or loose wiring in the reductant temperature sensor circuit, especially near connectors or where the harness passes through the DEF tank flange.
  2. A failing reductant temperature sensor that intermittently opens or shorts internally when exposed to vibration or temperature swings.
  3. Water or DEF contamination inside the sensor connector causing intermittent conductivity.
  4. Poor terminal tension at the sensor or powertrain control module connector, leading to an intermittent open circuit.
  5. A failing DEF tank heater element that draws excessive current and disturbs the sensor reference voltage.
  6. Rarely, a software glitch or internal fault in the powertrain control module that misinterprets a valid signal.

How to diagnose and fix it

  1. Inspect the reductant temperature sensor connector and the full wiring harness for chafing, corrosion, or loose pins, and repair as needed.
  2. Measure the sensor's resistance with a multimeter while wiggling the harness to check for intermittent changes; compare to the manufacturer's specification.
  3. Backprobe the sensor signal circuit at the powertrain control module and monitor for voltage drops or spikes while tapping on the sensor and harness.
  4. Check the DEF tank heater circuit for excessive current draw that could interfere with the sensor reference voltage.
  5. If the sensor is faulty, replace it according to the service procedure, which may require draining and refilling the DEF tank.
  6. Clear the diagnostic trouble codes and perform a road test, including cold starts and vibration-inducing conditions, to verify the repair.
  7. If the fault persists after sensor and wiring repairs, reprogram or replace the powertrain control module as a last resort.

Intermittent faults hide in plain sight

  • Many technicians replace the reductant temperature sensor only to find the real problem is a chafed wire hidden behind the DEF tank shield, so always perform a wiggle test before condemning the sensor.
  • A weak or failing battery or charging system can cause intermittent sensor codes across multiple modules, so verify stable voltage before diving into the DEF circuit.
  • The code can be set by a momentary loss of signal during a cold start when the DEF heater is commanded on, even if the sensor tests fine at room temperature.
  • Aftermarket DEF fluid with incorrect concentration can cause the sensor to behave erratically, so verify fluid quality before replacing parts.
  • Some vehicles require a relearn or adaptation reset after sensor replacement, and skipping this step can cause the code to return immediately.

Can I keep driving with P2046?

You can generally continue driving with P2046, but avoid long trips or heavy loads until the fault is repaired because an intermittent sensor can escalate to a complete failure and trigger reduced engine power. If the check engine light begins flashing or the vehicle enters limp mode, stop driving and seek service.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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