P21E0: Cylinder 3 Injector B Circuit Low

P21E0 reports a low circuit state on the B injector of cylinder 3. Mitsubishi lists it for the 2022 Eclipse Cross as the direct injector code and does not use the open code P21D1, so an interrupted wire and a short to ground both end up here once they last 2 s. Its procedure measures the injector across its two DI terminals at the intermediate connector, then the harness on both sides of that connector, and only then suspects the ECM. Port injector faults on the same cylinder are P0267 and P0268. On GM's 2019 LT5 V8 cylinder 3 is the second cylinder on the left bank; its supplemental injector fails this test with less than 0.5 Ohm between low side and ground in 20 of 25 samples while the driver is off, Type A in one trip. Expect a cylinder 3 misfire; P21E1 is the high 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 3 is numbered according to the manufacturer: check your engine's manual before working on it.

Symptoms

Check engine light on
Misfire on cylinder 3 (P0303)
Rough idle

Most likely causes

Cylinder 3 injector wire broken or shorted to ground
Injector of cylinder 3 with open or shorted coil
Engine control module output faulty

What to check, in order

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

Check the connector and wiring of the injector indicated
With the connector unplugged, check whether the signal wire is making contact with ground.
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 P21E0 means

P: Powertrain: engine and transmission
2: Generic code: same on every make
1: Air and fuel
E0: Specific fault in that system

Frequently asked questions

Can I keep driving with code P21E0?

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 P21E0?

The most common causes are: cylinder 3 injector wire broken or shorted to ground; injector of cylinder 3 with open or shorted coil; engine control module output faulty.

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.