What Does P205B Mean?
The DEF tank temperature sensor is providing readings that are implausible or inconsistent with other system parameters. The sensor signal is present but does not correlate properly with ambient temperature, engine temperature, or expected operating conditions.
Common Causes
40%
Faulty reductant tank temperature sensor providing inaccurate readings
25%
High resistance in sensor circuit wiring or connections
15%
Contaminated or crystallized DEF affecting sensor accuracy
12%
Sensor mounting issues causing poor thermal contact with fluid
8%
ECM software calibration issue or faulty ECM
Diagnostic Steps
1
Step 1: Monitor live data for DEF tank temperature and compare to ambient and engine coolant temperatures
2
Step 2: Check for correlation between temperature readings during cold start and normal operation
3
Step 3: Inspect DEF quality and check for contamination or crystallization in tank
4
Step 4: Measure sensor resistance at various temperatures and compare to specification chart
5
Step 5: Replace sensor if readings are consistently out of range, verify DEF quality is correct
Estimated Repair Cost
$200 - $500
Parts + labor, varies by vehicle and location
The DEF tank temperature sensor is providing readings that are implausible or inconsistent with other system parameters. The sensor signal is present but does not correlate properly with ambient temperature, engine temperature, or expected operating conditions.
The most common cause of P205B (Reductant Tank Temperature Sensor Circuit Range/Performance) is: Faulty reductant tank temperature sensor providing inaccurate readings
Typical repair costs for P205B range from $200 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive short distances but may limit vehicle performance. Continued operation may trigger DEF system shutdowns or prevent engine restart.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P205B to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control (SCR/DEF System)
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
