P205D: Reductant Tank Temperature Sensor A Circuit High

P205D is the top-of-range fault of the tank's temperature sensor. On voltage-read NTC sensors a high signal looks like extreme cold and typically comes from an open circuit, a lost ground or a short to supply: Ford's 2023 diesels set it above 4.3 V, GM's 2025 DEF controller above 4.75 V (about −40 °C, 0.5 s, Type A), and GM's 2018 diesel table above 60,000 Ω. On the 6.6L LML and 2014 Cruze GM reads a CAN raw value instead, where High means above 1022, i.e. 160 °C or more, the hot side (6 s, Type B). Ford's bulletin 18-2190 for 2011–2015 6.7L Super Duty treats P205D like P205C: new reductant heater and sender assembly plus PCM update. Hino names P205D next to P205B and P205C as a source of wrong DEF temperature input. The low end is P205C.

Symptoms

• MIL and DEF warning
• Tank heater runs although the tank is warm
• Dosing delayed after start

Most likely causes

• Open circuit, unplugged connector or broken ground
• Sensor in the heater/sender assembly open internally
• Signal wire shorted to supply voltage

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the AdBlue/DEF level and quality, and do not add additives or water
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Look for white crystals around the injector and the tank
4. Check connectors and heaters with the scanner
5. Run the dosing test available on your diagnostic tool
6. Replace parts only when the test points to that component

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P205D means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 0: Subsystem depends on the code range
• 5D: Specific fault in that system

Frequently asked questions

Can I keep driving with code P205D?

Deal with it soon. If the instrument cluster shows a countdown, the car may not restart once it reaches zero.

What causes code P205D?

The most common causes are: open circuit, unplugged connector or broken ground; sensor in the heater/sender assembly open internally; signal wire shorted to supply voltage.

Related codes

• P205AReductant Tank Temperature Sensor A Circuit
• P205CReductant Tank Temperature Sensor A Circuit Low
• P205BReductant Tank Temperature Sensor A Circuit Range/Performance
• P2043Reductant Temperature Sensor A Circuit Range/Performance
• P2ADCReductant Tank Temperature Sensor B Circuit High

Sources

• gsi.ext.gm.com: 25OBDG04A
• fordservicecontent.com: obd summary diesel 2023
• static.nhtsa.gov: MC 10144185 9999
• static.nhtsa.gov: MC 10184991 9999

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.