U02A5Lost Communication With Reductant Heater Control Module
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- At roughly -11 °C diesel exhaust fluid turns solid, while EU type approval asked for usable fluid within 20 minutes of a start at -15 °C, so tank, pump and lines carry heaters. Some systems leave their switching to a separate heater control module that reports state and temperatures to the engine or dosing controller. U02A5 is set when this module goes silent. No manufacturer documents U02A5 publicly. Many engines do without such a module: Ford's 2023 diesel summary drives the heaters straight from the engine controller and checks them with output codes such as P20BB, P20BC and P21DD. CARB 1968.2 requires every input to the inducement strategy to be monitored, and thaw control feeds it. In frost, dosing may start late, with a DEF warning and later inducement.
- What you may notice
- MIL and DEF system warning
- Dosing delayed in cold weather
- Inducement countdown if it persists
- Likely causes
- PossibleFuse, relay or supply of the heater module faulty
- PossibleWater or salt corrosion at the module connector near the tank
- PossibleShared bus disturbed by another faulty module
- RareHeater control module internally failed
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.