P21EB: Cylinder 8 Injector B Circuit High

P21EB is set when the cylinder 8 B injector circuit is shorted toward power. It closes GM's run of B-injector codes for the 2019 Corvette ZR1 LT5: the FICM sees the switched-off low side within 0.5 Ohm of supply in 20 of 25 samples and stores a Type A fault, lighting the MIL in the first trip. The supplemental injector of the right-rear cylinder can then no longer be opened, while the direct injector keeps working, so the car usually drives normally until high boost, where bank 2 may lean out. If several of these high codes appear together, a common feed or a shared connector is more likely than eight bad injectors. P21EA is the matching low fault, P0283 the A injector high fault and P0308 the misfire counter of this cylinder.

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

Symptoms

Check engine light on
Lean bank 2 under boost
Normal behaviour at part load

Most likely causes

Cylinder 8 B injector control wire shorted to a feed wire
Shared harness connector shorted when several injectors are affected
Injector coil shorted
Injection control module damaged

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 P21EB means

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

Frequently asked questions

Can I keep driving with code P21EB?

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 P21EB?

The most common causes are: cylinder 8 B injector control wire shorted to a feed wire; shared harness connector shorted when several injectors are affected; injector coil shorted.

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.