P21D0: Cylinder 2 Injector B Circuit/Open

What does P21D0 mean?

P21D0 is the open-circuit code for the B injector of cylinder 2. Where that cylinder sits varies: GM's small-block V8 alternates odd and even numbers between the banks, so cylinder 2 opens the right bank, while Ford's V6 and V8 count one bank first and place it next to cylinder 1. Ford defines B as the port injector, the direct injector being A with P0202. Ford runs the check in every engine with combined port and direct injection, from the three-cylinder 1.5 to the 5.0 V8, continuously at 11 V or more for 5 s. GM's LT5 injection module samples the circuit every 100 ms once the powertrain relay supplies at least 11 V. On engines that run on port fuel alone at light load, like Ford's second 3.5 EcoBoost, the cylinder then misfires mostly at idle. Low and high faults are P21DE and P21DF.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Misfire on cylinder 2, mainly at idle and light load
• Code P0302 stored as well

Common causes

• High Port injector of cylinder 2 with an open winding
• Medium Broken wire or pushed-back terminal in the injector harness
• Low Output stage in the engine or injection module failed

Likelihood is a general estimate across vehicles; your make and model may differ.