Powertrain, generic (extended)

P20C6 Reductant Heater D Control Circuit Performance

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

P20C6 is the functional check of heater D. FCA documents it for the 3.0 L EcoDiesel under the name Reductant Heater 4 Control Circuit Performance: bulletin 18-068-20 reflashed 2017 Ram 1500 engine computers that showed it, and a 2021 STAR case for 2020–2021 Ram 1500, Wrangler and Gladiator notes that it turns up mostly in severe cold, often without a defect. FCA asks technicians to confirm that ambient and tank temperatures read above 4 °C, inspect the supply line to the injector and run a dosing quantity test, which should capture 26–35 ml, before replacing anything; many returned pumps showed no fault. Deutz lists the code for its downstream line heater with an undetermined root cause (FMI 11). Only a failed dosing test or a leaking line justifies new parts.

Likely causes

False detection in extreme cold with a still-frozen tank (FCA STAR S2118000006)

Outdated engine control software (FCA 18-068-20)

Leaking or blocked DEF supply line to the injector

DEF pump unable to build pressure or injector delivering the wrong quantity

Symptoms

Malfunction indicator lamp, mostly after very cold nights
DEF system message, sometimes alongside pressure codes
Often no noticeable change in how the vehicle drives

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€0–1,500

Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant line heater d

References: static.nhtsa.gov, static.nhtsa.gov, serdia.deutz.com.