P20B1 code meaning
Reductant Heater Coolant Control Valve Circuit/Open
Powertrain system Generic code P20xx codes Check engine light
What P20B1 means
Many heavy-duty SCR systems thaw the DEF tank and supply module with engine coolant, and an electrically switched valve decides when that warm coolant may circulate; Bosch offers its larger supply modules with either electric or cooling-water heating. P20B1 is set when the control unit finds the drive circuit of this valve open or otherwise defective. No manufacturer documents P20B1 publicly. Hino, which fits such a coolant cutoff valve, explains in TT-16-014 that once its dosing control unit detects an open load it stops powering the valve until a UREA SCR memory reset, so circuit tests only work while the valve stays connected. Without a working valve, DEF stays frozen longer in winter.
P20B1 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P20B1
- Malfunction indicator and SCR warning on
- DEF thaws slowly or not at all in cold weather
- Valve does not click during an actuator test
Common causes of P20B1
- Most likelyValve connector unplugged, loose or corroded
- PossibleOpen solenoid coil in the coolant valve
- PossibleBroken wire between control unit and valve
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant coolant valve
What each part of P20B1 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. |
| B1 | The exact fault in that area. |
What to do next
- Note P20B1 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 P20B1
What does P20B1 mean?
P20B1 means "Reductant Heater Coolant Control Valve Circuit/Open". Many heavy-duty SCR systems thaw the DEF tank and supply module with engine coolant, and an electrically switched valve decides when that warm coolant may circulate; Bosch offers its larger supply modules with either electric or cooling-water heating. It is a generic code, so it means the same on every make.
Is it safe to drive with P20B1?
Drive gently and only to a workshop. With P20B1 the car can go into limp mode (reduced power) to protect itself.
Will P20B1 fail an emissions test?
Yes, it can. P20B1 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 P20B1 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will P20B1 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.