Emissions

P2055 — Reductant (DEF/AdBlue) Tank Temperature Sensor Circuit High

Severity: medium Drive with care, to a shop

What P2055 means

The engine control unit constantly reads the temperature sensor in the reductant (DEF/AdBlue) tank. The SCR system uses it to decide when to heat the tank and whether dosing is allowed. P2055 sets when the sensor circuit voltage stays above the expected range, which usually points to an open circuit or a short to positive.

Symptoms

  • Check engine light on
  • SCR or AdBlue/DEF warning on the dash
  • SCR system faults stored in the ECU
  • Possible engine start countdown
  • Reduced torque on some vehicles
  • Increased NOx emissions

Possible causes

  1. Open circuit in the temperature sensor wiring
  2. Failed tank temperature sensor
  3. Unplugged or corroded tank module connector
  4. Signal wire shorted to positive voltage
  5. Damaged harness near the tank
  6. Faulty tank module or SCR control unit (rare)

How to diagnose

  1. Read codes and freeze frame data, and check dosing system status and the tank temperature reading
  2. Compare the scan tool tank temperature with actual ambient temperature on a cold vehicle
  3. Check reductant level and quality, looking for crystals or contamination
  4. Inspect the tank module connector for a loose fit, corrosion or bent pins
  5. Inspect the harness from the tank to the ECU for chafing or past repairs
  6. Unplug the sensor and measure reference voltage and sensor resistance against specs
  7. Test the signal wire for a short to positive and for an open circuit
  8. Check for technical bulletins and software updates for your model

Common fixes

  • Repair or replace the damaged connector and wiring
  • Replace the tank module with the temperature sensor
  • Repair the short to positive in the harness
  • Update the ECU software if the manufacturer offers it
  • Clear the codes and confirm SCR operation on a test drive

Questions and answers

What does P2055 mean?

The ECU is getting too high a voltage from the DEF/AdBlue tank temperature sensor. The usual causes are an open circuit, a poor connector or a failed sensor.

Can I drive with P2055?

For a short time, yes, but the SCR system may run with limits. On some vehicles a start countdown or reduced power follows the warnings, so repair it soon.

Will adding AdBlue fix P2055?

Usually not. The fault is in the temperature sensor's electrical circuit, not the fluid level. Check the connector, wiring and sensor first.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.