P21CF: Cylinder 1 Injector B Circuit/Open
Standardized SAE J2012 code · P21xx — Fuel & air metering and auxiliary emission controls
What does P21CF mean?
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.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Check engine light on
- Rough idle or misfire on cylinder 1, often with P0301
- Further harness codes stored at the same time
Common causes
- High Chafed or broken wire in the port injector harness (on the Bronco Sport near the transmission cover)
- Medium Open coil in the cylinder 1 port injector
- Medium Loose or corroded plug at the injector
- Low Faulty driver stage in the engine module or separate injector module
Likelihood is a general estimate across vehicles; your make and model may differ.
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