P20C6 code meaning
Reductant Heater D Control Circuit Performance
Powertrain system Generic code P20xx codes Check engine light
What P20C6 means
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.
P20C6 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P20C6
- Malfunction indicator lamp, mostly after very cold nights
- DEF system message, sometimes alongside pressure codes
- Often no noticeable change in how the vehicle drives
Common causes of P20C6
- Most likelyFalse detection in extreme cold with a still-frozen tank (FCA STAR S2118000006)
- PossibleOutdated engine control software (FCA 18-068-20)
- PossibleLeaking or blocked DEF supply line to the injector
- Less likelyDEF pump unable to build pressure or injector delivering the wrong quantity
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant line heater d
What each part of P20C6 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| C6 | The exact fault in that area. |
What to do next
- Note P20C6 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 P20C6
What does P20C6 mean?
P20C6 means "Reductant Heater D Control Circuit Performance". P20C6 is the functional check of heater D. It is a generic code, so it means the same on every make.
Is it safe to drive with P20C6?
Drive gently and only to a workshop. With P20C6 the car can go into limp mode (reduced power) to protect itself.
Will P20C6 fail an emissions test?
Yes, it can. P20C6 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 P20C6 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P20C6 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.