What Does P205A Mean?
The powertrain control module has detected a malfunction in the electrical circuit for the diesel exhaust fluid (DEF) tank temperature sensor. This indicates a general circuit fault that prevents the sensor from communicating properly with the ECM.
Common Causes
35%
Damaged or corroded wiring harness/connectors at DEF tank sensor
30%
Faulty reductant tank temperature sensor
20%
Water intrusion or corrosion in sensor connector
10%
Broken or chafed wiring between sensor and ECM
5%
ECM internal fault or poor ground connection
Diagnostic Steps
1
Step 1: Visually inspect DEF tank temperature sensor connector for corrosion, moisture, or damage
2
Step 2: Check wiring harness from sensor to ECM for chafing, breaks, or shorts to ground/power
3
Step 3: Measure sensor resistance and compare to manufacturer specifications at ambient temperature
4
Step 4: Test circuit voltage and ground integrity at sensor connector with harness connected
5
Step 5: Replace sensor if circuit tests pass but code persists, then retest system
Estimated Repair Cost
$150 - $450
Parts + labor, varies by vehicle and location
The powertrain control module has detected a malfunction in the electrical circuit for the diesel exhaust fluid (DEF) tank temperature sensor. This indicates a general circuit fault that prevents the sensor from communicating properly with the ECM.
The most common cause of P205A (Reductant Tank Temperature Sensor Circuit) is: Damaged or corroded wiring harness/connectors at DEF tank sensor
Typical repair costs for P205A range from $150 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle remains safe to drive but may enter reduced power mode. Extended operation can result in increased emissions and potential DEF system damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P205A 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
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