P205B: Diesel exhaust fluid tank temperature sensor signal out of range or not plausible
Reductant tank temperature sensor circuit range/performance
Severity: Severity not verified — if the car runs badly, have it inspected
The sources read list causes and symptoms but give no driving-risk rating. On SCR trucks a DEF fault can bring other SCR codes, so check what else is stored.
P205B in short
P205B means the engine computer sees a diesel exhaust fluid tank temperature sensor reading that is out of range or does not make sense. Likely causes are a failed sensor, open or shorted wiring, or occasionally the SCR controller. It applies to diesels with an SCR system.
Diesel trucks with selective catalytic reduction (SCR) inject diesel exhaust fluid (DEF) to cut nitrogen oxides. The DEF tank has a temperature sensor so the system knows whether the fluid is frozen or warm enough to use.
P205B sets when that sensor's signal is outside the expected range. Kelley Blue Book describes the out-of-range voltage; both references list the sensor and its wiring first.
Check for other SCR codes stored at the same time before replacing parts.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Failed DEF tank temperature sensor
Common general cause- Why it ranks here
- Both TroubleCodes.net and Kelley Blue Book list the tank temperature sensor as a cause.
- What would change this
- Rises if the reading is stuck or the sensor tests out of spec. Falls if it reads sensibly against ambient temperature.
Cause 2: Open or shorted wiring or connector in the sensor circuit
Common general cause- Why it ranks here
- Both references list the sensor wiring. Kelley Blue Book specifically names open or shorted circuits.
- What would change this
- Rises if a wiring test finds a short, open or damaged connector. Falls if the wiring tests fine.
Cause 3: SCR controller or engine computer fault, or programming
Possible — needs testing- Why it ranks here
- Both references list the computer last. Volvo SP-284-042 names P205B in a software update for 2013 trucks, but its summary does not define the code.
- What would change this
- Rises only if sensor and wiring test good, or if a dealer finds an update for the VIN. Falls otherwise.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read all codes and note whether other DEF or SCR codes are stored with P205B.
IfOther SCR codes are stored
It meansWork the SCR codes together; a shared wiring or software fault is possible.
IfP205B is alone
It meansTest the sensor circuit.
Step 2: Compare the DEF tank temperature reading with ambient temperature, then test the sensor and wiring with a multimeter.
Warning:The DEF tank sits near hot exhaust parts and DEF can irritate skin and eyes. Let a shop do it unless you are experienced.
IfThe sensor reads stuck or out of range
It meansSensor fault.
IfThe sensor tests good but the wiring shows an open or short
It meansWiring fault.
Points to: Open or shorted wiring or connector in the sensor circuit
IfBoth test good
It meansAsk a dealer about software.
Points to: SCR controller or engine computer fault, or programming
Symptoms
- Check engine light
- Other SCR or diesel exhaust fluid codes stored
- Reduced performance on some trucks
How to fix
Parts and cost context
- Engine control module (ECM / PCM):The sensor and wiring are tested before the controller. Labour varies; get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
We don't have reviewed vehicle-specific evidence for P205B yet. The causes and tests above apply across vehicles.
Related codes
No curated relationships for P205B yet.
Sources and review
- P205B trouble code page
- P205B OBD-II code
- Volvo SP-284-042: ECM and ACM software updates for P1086, P0420, P205B, P2002
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error