P20D8 code meaning
Exhaust Aftertreatment Fuel Supply Control Performance
Powertrain system Generic code P20xx codes Check engine light
What P20D8 means
The supply valve ahead of the exhaust doser is electrically sound, but the pressure it produces in the feed line does not follow its commands. A typical layout, described in a patent assigned to International Engine, measures that line pressure and uses it both to meter the dose and to diagnose the regulating valve. Hino's J08E manual lists P20D8 among the codes to resolve before chasing a regeneration fault; its trucks use a fuel cut valve ahead of the dosing injector. CARB treats a supply that runs out of control authority as a feedback fault. Circuit faults are P20D7, P20D9 and P20DA; a valve fixed open or shut is P20DB or P20DC.
P20D8 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P20D8
- Check engine light on
- Regenerations take longer or fail
Common causes of P20D8
- Most likelySluggish or contaminated supply valve
- PossibleLow feed pressure from a clogged fuel filter or weak low-pressure pump
- Less likelyLine pressure sensor reading off
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Aftertreatment fuel supply solenoidAftertreatment fuel pump
What each part of P20D8 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. |
| D8 | The exact fault in that area. |
What to do next
- Note P20D8 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 P20D8
What does P20D8 mean?
P20D8 means "Exhaust Aftertreatment Fuel Supply Control Performance". The supply valve ahead of the exhaust doser is electrically sound, but the pressure it produces in the feed line does not follow its commands. It is a generic code, so it means the same on every make.
Is it safe to drive with P20D8?
Drive gently and only to a workshop. With P20D8 the car can go into limp mode (reduced power) to protect itself.
Will P20D8 fail an emissions test?
Yes, it can. P20D8 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 P20D8 to fix?
Difficulty: hard. A typical repair takes 1 to 3 hours of work. This is a job for a workshop.
Will P20D8 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.