P21D1: Cylinder 3 Injector B Circuit/Open
Standardized SAE J2012 code · P21xx — Fuel & air metering and auxiliary emission controls
What does P21D1 mean?
P21D1 concerns the B injector of cylinder 3, which on Ford's 1.5 EcoBoost three-cylinder is the last one in the block. That engine combines port and direct fuel, and Ford names the port injectors B. Bulletin SSM 49996 for the 2021 Bronco Sport describes P21CF, P21D0 and P21D1 appearing together with transmission and other codes, in some cases with a no-crank condition, because the harness was damaged at the transmission cover; when all three B codes show at once, a shared wiring fault is far more likely than three bad injectors. Ford's summary checks the B circuits continuously above 11 V within 5 s. GM's LT5 V8 module flags an open low side once 20 of 25 samples fail. The direct injector of the cylinder is coded P0203.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Check engine light on
- Rough running or misfire on cylinder 3
- With harness damage also transmission codes or no crank
Common causes
- High Harness damage affecting several injectors at once (Ford Bronco Sport, transmission cover)
- Medium Open coil in the cylinder 3 port injector
- Low Connector not latched or corroded
Likelihood is a general estimate across vehicles; your make and model may differ.
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