P205B code meaning
Reductant Tank Temperature Sensor A Circuit Range/Performance
Powertrain system Generic code P20xx codes Check engine light
What P205B means
P205B is the rationality check of the DEF tank temperature: after a long cold soak every sensor should read about the same, so a tank value far off the rest is flagged. GM's 6.6L LML compares it with fuel temperature after 28,800 s engine off (beyond +35/−35 °C, Type B); GM's 2018 diesel table uses the exhaust gas temperature average (>35 °C, Type A), and the 2025 DEF controller needs at least four reference sensors and over 8 h off (>30 °C, Type A). Ford's 2023 diesels compare it with the quality sensor at start (>40 °C), VW's Touareg with outside air. Volvo/Mack (KC-2107) have it re-run before replacing the level sensor, and Ford (2019 6.7L), Land Rover (2016 TDV6) and GM (2021–22 3.0L) cured cases by software. Circuit faults are P205C/P205D.
P205B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.4 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P205B
- MIL, sometimes with an emissions service message
- Usually no change in driving
Common causes of P205B
- Most likelyCalibration error, fixed by reprogramming
- PossibleTank temperature sensor reading off (offset or gain)
- PossibleFrozen tank or low fill level distorting the reading
- Less likelyFaulty reference sensor (fuel, exhaust or quality sensor)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant tank temperature sensor
What each part of P205B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| 5B | The exact fault in that area. |
What to do next
- Note P205B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P205B
What does P205B mean?
P205B means "Reductant Tank Temperature Sensor A Circuit Range/Performance". P205B is the rationality check of the DEF tank temperature: after a long cold soak every sensor should read about the same, so a tank value far off the rest is flagged. It is a generic code, so it means the same on every make.
Is it safe to drive with P205B?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P205B fail an emissions test?
Yes, it can. P205B is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P205B to fix?
Difficulty: medium. A typical repair takes 0.4 to 3 hours of work. This is a job for a workshop.
Will P205B clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.