P20D4 code meaning
Exhaust Aftertreatment Fuel Injector B Control Circuit High
Powertrain system Generic code P20xx codes Check engine light
What P20D4 means
On the second exhaust fuel doser (B), the control line sits at or near battery voltage, so the driver cannot pull it low to open the valve. No manufacturer documents P20D4 publicly. For injector A, GM's diesel tables flag excess current in the switched-on state as a short to power and rate it Type B (P20CE). With doser B out of action, the share of the exhaust it serves no longer gets enough heat for regeneration. CARB requires circuit monitoring for every electronic part of an in-exhaust injection system. For the same doser, P20D1 covers a broken line and P20D3 a grounded one.
P20D4 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 P20D4
- Check engine light on
- Regeneration impaired, soot load rising
Common causes of P20D4
- Most likelyControl wire to doser B shorted to a powered circuit
- PossibleShorted turns in the doser B solenoid
- Less likelyFaulty output stage in the control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Aftertreatment fuel injector
What each part of P20D4 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. |
| D4 | The exact fault in that area. |
What to do next
- Note P20D4 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 P20D4
What does P20D4 mean?
P20D4 means "Exhaust Aftertreatment Fuel Injector B Control Circuit High". On the second exhaust fuel doser (B), the control line sits at or near battery voltage, so the driver cannot pull it low to open the valve. It is a generic code, so it means the same on every make.
Is it safe to drive with P20D4?
Drive gently and only to a workshop. With P20D4 the car can go into limp mode (reduced power) to protect itself.
Will P20D4 fail an emissions test?
Yes, it can. P20D4 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 P20D4 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will P20D4 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.