P056DReductant Control Module System Voltage
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- Diesels with SCR may have a separate module for AdBlue/DEF dosing (pump, heaters, dosing valve) talking to the engine module over CAN. It measures its supply; outside its window no safe dosing is possible, so dosing and SCR diagnoses are suspended and NOx rises, and if it persists the SCR warnings and power limits apply. No manufacturer document available to us uses P056D – Ford's diesel reports the dosing module supply as P21CB below 8.5 V and P21CC above 19 V. CARB requires SCR modules to be monitored.
- What you may notice
- Check engine light and DEF warning
- Possible countdown to start inhibit or power limit
- Further SCR codes
- Likely causes
- LikelyFuse, relay or supply line of the DEF module
- PossibleCorrosion at module connector or ground (underbody, road salt)
- PossibleSystem under- or overvoltage
- RareModule faulty
- 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: €30 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.