P21E7: Cylinder 6 Injector B Circuit High

P21E7 is stored when the B injector of cylinder 6 shows a short toward power. GM's 2019 Corvette ZR1 with the LT5 V8 is the documented user; there the FICM checks the low side only in the driver-off state, flags 0.5 Ohm or less to power, and needs at least 11 V at the powertrain relay with the engine running. The result is a Type A fault after one trip. With the low side tied to supply, every switching attempt would push current straight into the driver, so the injector on the right-bank cylinder 6 delivers nothing. A useful check is to unplug the injector: if the voltage on the control wire stays, the harness is at fault; if it disappears, the injector coil is suspect. P21E6 is the matching low fault and P0277 the A injector high code.

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

Symptoms

Check engine light on
Lean condition on bank 2 under load
Cylinder 6 misfire at high load

Most likely causes

Cylinder 6 B injector control wire in contact with a live wire
Shorted turns in the injector coil
Output stage of the injection control module damaged by the short

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 affects emissions.

What each character of P21E7 means

P: Powertrain: engine and transmission
2: Generic code: same on every make
1: Air and fuel
E7: Specific fault in that system

Frequently asked questions

Can I keep driving with code P21E7?

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 P21E7?

The most common causes are: cylinder 6 B injector control wire in contact with a live wire; shorted turns in the injector coil; output stage of the injection control module damaged by the short.

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.