A faulty reductant tank temperature sensor with an internal intermittent connection or failing thermistor element.; Damaged, chafed, or corroded wiring in the sensor circuit, especially near the tank or where the harness flexes.; Loose or contaminated electrical connectors at the sensor or PCM, causing an erratic signal.; Water or DEF intrusion into the connector or sensor housing, leading to shorting or resistance changes.; A failing PCM driver circuit for the sensor, though this is less common than sensor or wiring issues.; Extreme temperature fluctuations or DEF freezing and expanding, which can stress the sensor and its wiring.

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P205E

P205EReductant Tank Temperature Sensor A Circuit Intermittent/Erratic

P205E indicates that the powertrain control module (PCM) has detected an intermittent or erratic signal from the reductant tank temperature sensor 'A' circuit, which monitors the temperature of the diesel exhaust fluid (DEF) tank. The PCM expects a steady voltage or resistance value from this sensor, and when the signal jumps, drops out, or behaves unpredictably, the code is stored.

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 (malfunction indicator lamp, MIL), often with no other noticeable symptoms.
A driver information message warning of poor DEF quality or a DEF system fault.
Possible reduction in engine power or speed limiting if the fault persists and the system enters limp mode.
Inconsistent or inaccurate DEF level and temperature readings on the dashboard gauge.
Difficulty clearing the code, as it may reset immediately after clearing if the intermittent fault is still present.

Common causes, most likely first

A faulty reductant tank temperature sensor with an internal intermittent connection or failing thermistor element.
Damaged, chafed, or corroded wiring in the sensor circuit, especially near the tank or where the harness flexes.
Loose or contaminated electrical connectors at the sensor or PCM, causing an erratic signal.
Water or DEF intrusion into the connector or sensor housing, leading to shorting or resistance changes.
A failing PCM driver circuit for the sensor, though this is less common than sensor or wiring issues.
Extreme temperature fluctuations or DEF freezing and expanding, which can stress the sensor and its wiring.

How to diagnose and fix it

Use a scan tool to record live data from the reductant tank temperature sensor and look for erratic or implausible values while wiggling the harness and connectors.
Visually inspect the sensor, its wiring, and connectors for damage, corrosion, or DEF residue, and repair or replace as needed.
Perform a resistance test on the sensor at known temperatures and compare to specifications to confirm the sensor is stable and within range.
Check for continuity and short-to-ground or short-to-power on each wire of the sensor circuit, repairing any faults found.
If wiring and sensor test good, substitute a known-good sensor or simulate the signal with a resistor box to see if the code returns.
Clear the code and perform a road test or drive cycle to verify the repair, monitoring live data for stability.
If the fault persists after all external checks, diagnose the PCM and its connections, replacing or reprogramming only as a last resort.

Intermittent sensor faults that fool technicians

A common misdiagnosis is replacing the sensor when the real problem is a chafed wire hidden inside the loom where it rubs against the frame or tank bracket.
The code can be set by a momentary glitch that occurs only when the vehicle is cold or after a rough road, so the sensor may test perfectly when the engine is warm.
DEF crystallization around the sensor connector can create an intermittent short that appears only in damp weather, so look for white residue.
Some vehicles use the same sensor for both temperature and level, and a failing level circuit can cause erratic temperature readings that set P205E.
A weak battery or charging system can cause voltage spikes that confuse the PCM and set intermittent sensor codes, so always check system voltage first.

Can I keep driving with P205E?

You can generally continue driving with P205E, but avoid long trips or heavy loads until it is repaired because the fault may escalate to a derate or limp mode. If the engine warning light begins flashing or power is noticeably reduced, have the vehicle checked promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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