P20C0 code meaning
Reductant Heater B Control Circuit High
Powertrain system Generic code P20xx codes Check engine light
What P20C0 means
P20C0 reports that heater B's control circuit is high, typically a wire touching a battery feed or a driver that will not switch off. On Ford diesels B is the pressure line heater: with the power stage off, a current below 3 A while the output still carries over 5 V triggers it, and the glow plug module flags the condition in 250 ms. GM's 2025 tables test heater 2 (line heater) with the output off and an elevated voltage window, Type A with a two-second filter; the 2018 tables use a short-to-battery status from the DEF control module. VW uses more than 2.20 A reported by the power stage on the Touareg CNRB, and Deutz FMI 3 for its pressure line heater. A line heater that is powered all the time can overheat the hose, while one the module has shut down leaves it frozen.
P20C0 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P20C0
- Malfunction indicator lamp and DEF warning
- Line heater may stay on with the engine off, draining the battery
- Frozen pressure line once the module disables the heater
Common causes of P20C0
- Most likelyLine heater control wire shorted to a positive feed
- PossibleHeater output stage in the DEF, engine or glow plug module stuck on
- Less likelyBridged pins in a shared connector next to a supply terminal
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant line heater b
What each part of P20C0 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. |
| C0 | The exact fault in that area. |
What to do next
- Note P20C0 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 P20C0
What does P20C0 mean?
P20C0 means "Reductant Heater B Control Circuit High". P20C0 reports that heater B's control circuit is high, typically a wire touching a battery feed or a driver that will not switch off. It is a generic code, so it means the same on every make.
Is it safe to drive with P20C0?
Drive gently and only to a workshop. With P20C0 the car can go into limp mode (reduced power) to protect itself.
Will P20C0 fail an emissions test?
Yes, it can. P20C0 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 P20C0 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P20C0 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.