U05A6 code meaning
Invalid Data Received From Reductant Heater Control Module
Network system Generic code U05xx codes Check engine light
What U05A6 means
Diesel exhaust fluid freezes at about -11 °C, and EU rules demanded that it be usable within 20 minutes after a start at -15 °C, so tanks, pumps and lines get electric heaters. Where these heaters are driven by a separate control module, it reports heater states, temperatures and faults to the engine or dosing controller over the bus. U05A6 is stored when those reports arrive but are inconsistent or corrupt. No manufacturer documents this code publicly. CARB 1968.2 requires every component that feeds the emission control or its inducement to be monitored, which covers thaw control. U02A5 means the module is silent, P20B9 points to a heater circuit itself. In cold weather, dosing may start late and warnings may appear.
U05A6 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairAfter a drive cycle
Symptoms of U05A6
- Check engine light or DEF system warning
- Delayed DEF dosing after cold starts
Common causes of U05A6
- PossibleHeater control module electronics faulty
- PossibleWater or salt corrosion at module connector or bus wiring
- Less likelySoftware levels of heater module and engine controller do not fit
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant heater module
What each part of U05A6 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A6 | The exact fault in that area. |
What to do next
- Note U05A6 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 U05A6
What does U05A6 mean?
U05A6 means "Invalid Data Received From Reductant Heater Control Module". Diesel exhaust fluid freezes at about -11 °C, and EU rules demanded that it be usable within 20 minutes after a start at -15 °C, so tanks, pumps and lines get electric heaters. It is a generic code, so it means the same on every make.
Is it safe to drive with U05A6?
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 U05A6 fail an emissions test?
Yes, it can. U05A6 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 U05A6 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will U05A6 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.