P21E1: Cylinder 3 Injector B Circuit High

What does P21E1 mean?

P21E1 is the high fault on the cylinder 3 B injector circuit. In Mitsubishi's 2022 Eclipse Cross that is the direct high-pressure injector, and the module reacts to a short circuit lasting 2 s, checked with 10 to 16.5 V battery voltage. To confirm a repair, the manual points to its OBD drive cycle pattern 1. GM's 2019 LT5 V8 monitors the low side of the supplemental cylinder 3 injector in its separate FICM module and flags under 0.5 Ohm toward power as Type A with the MIL in the first trip. A short to power keeps the low side from ever reaching ground, so the injector cannot open, and switching against the short can strain the driver stage. P21E0 covers the low fault and P0268 the port injector high fault on Mitsubishi; a cylinder 3 misfire often follows.

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

Symptoms

• Check engine light on
• Cylinder 3 not firing properly
• Torque reduction if several injectors fail (Mitsubishi)

Common causes

• High Cylinder 3 injector line shorted to supply voltage
• Medium Shorted injector coil
• Low Damaged driver in the control module

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