P21DF: Cylinder 2 Injector B Circuit High

P21DF is set when the cylinder 2 B injector circuit shows a short toward supply. Mitsubishi's 2022 Eclipse Cross applies it to the direct high-pressure injector and stores it after a 2 s short with the ignition on and the driver supply above 10 V; troubleshooting first inspects the negative DI wire of cylinder 2 up to the engine module and names the injector, the harness and the ECM as possible causes. The fail-safe is graded: with one cylinder affected, both injectors of that cylinder stop; with several, the engine falls back to port injection and torque is limited. GM's 2019 LT5 V8 judges the same title on its supplemental injector by less than 0.5 Ohm toward power on the low side, Type A. The port injector high code of this Mitsubishi cylinder would be P0265; P21DE is the low fault.

Medium severity. Can I keep driving?Drive as little as possible and go to a repair shop. If you smell fuel or the engine is shaking badly, do not keep driving.

Cylinder 2 is numbered according to the manufacturer: check your engine's manual before working on it.

Symptoms

Check engine light on
Cylinder 2 switched off or misfiring
Less pulling power with multiple faults

Most likely causes

Negative injector line of cylinder 2 shorted to supply
Injector coil shorted
ECM or injection module driver defective

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and wiring of the injector indicated
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Measure the resistance and compare it with the manufacturer's specification
Check the control signal with an oscilloscope; on direct injection or diesel engines, leave this to a repair shop because of the high voltages
On diesels, check the per-cylinder injection corrections

Good to know

Repair difficulty: hard
It can trigger limp mode.
It affects emissions.

What each character of P21DF means

P: Powertrain: engine and transmission
2: Generic code: same on every make
1: Air and fuel
DF: Specific fault in that system

Frequently asked questions

Can I keep driving with code P21DF?

Drive as little as possible and go to a repair shop. If you smell fuel or the engine is shaking badly, do not keep driving.

What causes code P21DF?

The most common causes are: negative injector line of cylinder 2 shorted to supply; injector coil shorted; eCM or injection module driver defective.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.