P21CF code meaning
Cylinder 1 Injector B Circuit/Open
Powertrain system Generic code P21xx codes Check engine light
What P21CF means
P21CF flags an open drive circuit of the second injector on cylinder 1. Which of the two injectors is B depends on the maker: Ford gives the letter to the port injector and keeps A, coded P0201, for direct injection, whereas Mitsubishi calls its direct injectors B and files open circuits under the low code P21DB. Ford's 2020 to 2025 gasoline summaries test the B circuits continuously above 11 V and need 5 s. GM's 2019 LT5 V8 judges it in a separate injection module: over 200 kOhm on the switched-off low side in 20 of 25 samples, Type A with the MIL in the first trip. Ford bulletin SSM 49996 lists it with P21D0 and P21D1 on 2021 Bronco Sport 1.5 models with a harness damaged at the transmission. With direct injection still working, rough idle or P0301 is the usual sign.
P21CF at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P21CF
- Check engine light on
- Rough idle or misfire on cylinder 1, often with P0301
- Further harness codes stored at the same time
Common causes of P21CF
- Most likelyChafed or broken wire in the port injector harness (on the Bronco Sport near the transmission cover)
- PossibleOpen coil in the cylinder 1 port injector
- PossibleLoose or corroded plug at the injector
- Less likelyFaulty driver stage in the engine module or separate injector module
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 P21CF 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. |
| CF | The exact fault in that area. |
What to do next
- Note P21CF 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 P21CF
What does P21CF mean?
P21CF means "Cylinder 1 Injector B Circuit/Open". P21CF flags an open drive circuit of the second injector on cylinder 1. It is a generic code, so it means the same on every make.
Is it safe to drive with P21CF?
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 P21CF fail an emissions test?
Yes, it can. P21CF 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 P21CF to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P21CF clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.