P221EReductant Heater C Current Too Low
- 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
- P221E says DEF heater C pulls too little current while commanded on. Which element is C depends on the system. In GM's 2025 Duramax tables heater 3 is a second tank heater; the code needs a PWM command above zero and trips under 0.75 A after 40 readings taken every 0.1 s, a Type A fault with the MIL after one trip. GM's 2014 tables for the 6.6L LML gave the letter to the heater in the supply (pump) module instead: conductance of 0.14 S or less, checked once per trip with the battery at 11 V or more, Type B. Ford's 2023 diesel summary has a heater C only with a supply voltage check (P20C2) and does not list P221E. In frost the thawing of DEF around that heater is slow. P221F is the high-current partner, P20C1 the open control circuit.
- What you may notice
- Malfunction indicator lamp on
- Slow DEF thawing in cold weather, dosing starts late
- Likely causes
- LikelyHeater C element open or burnt (tank or supply module, by system)
- PossibleCorroded or wet connector at the tank or pump unit
- RareHeater supply missing (fuse, relay, harness)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.