P21D2 code meaning
Cylinder 4 Injector B Circuit/Open
Powertrain system Generic code P21xx codes Check engine light
What P21D2 means
P21D2 reports an open in the drive circuit of the B injector on cylinder 4. On four-cylinder engines with dual injection it is the last of the set, for example Ford's 2.0 EcoBoost from 2022 or the 2.3 introduced for the 2024 Mustang, both of which added port injectors to direct injection. Ford tests it like its siblings, continuously with at least 11 V and a 5 s window, and assigns letter A to the direct injector (P0204). Mitsubishi, whose Eclipse Cross uses B for the direct injectors, has no open code here and files such faults under the low code P21E2. On Ford's 3.5 V6 cylinder 4 opens the second bank. In GM's 2019 LT5 module the check samples every 100 ms. Expect a misfire on cylinder 4.
P21D2 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P21D2
- Check engine light on
- Misfire on cylinder 4 (P0304)
- Uneven idle
Common causes of P21D2
- Most likelyOpen winding in the cylinder 4 port injector
- PossibleWire broken at a bend or clip near the intake manifold
- PossibleCorroded or loose injector connector
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injectorInjector wiringEngine control module
What each part of P21D2 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 1 | Area: fuel and air metering. |
| D2 | The exact fault in that area. |
What to do next
- Note P21D2 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 P21D2
What does P21D2 mean?
P21D2 means "Cylinder 4 Injector B Circuit/Open". P21D2 reports an open in the drive circuit of the B injector on cylinder 4. It is a generic code, so it means the same on every make.
Is it safe to drive with P21D2?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P21D2 fail an emissions test?
Yes, it can. P21D2 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 P21D2 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P21D2 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.