P21EA: Cylinder 8 Injector B Circuit Low

P21EA is the ground-short code for the B injector of cylinder 8 and the last low code in GM's 2019 FICM table for the Corvette ZR1 LT5, because the V8 ends there. Cylinder 8 is the rearmost of the right bank (bank 2). The module flags 0.5 Ohm or less between the switched-off low side and ground in 20 of 25 samples of 100 ms, with the engine running and 11 V or more at the powertrain relay, as a Type A fault. Mitsubishi's four-cylinder dual-injection engine never reaches this code, and Ford treats a B-injector short on cylinder 8 as P21D6. A grounded low side can hold the injector open, so bank 2 runs rich and fuel can wash the cylinder wall. P21EB is the high fault; the A injector low fault is P0282.

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

Symptoms

• Check engine light on
• Rich running on bank 2
• Hard hot start or misfire on cylinder 8

Most likely causes

• Cylinder 8 B injector wiring chafed through to ground
• Water or corrosion in the cylinder 8 injector plug
• Injector shorted to its body
• FICM driver stuck on

What to check, in order

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

1. Check the connector and wiring of the injector indicated
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Measure the resistance and compare it with the manufacturer's specification
4. Check the control signal with an oscilloscope; on direct injection or diesel engines, leave this to a repair shop because of the high voltages
5. On diesels, check the per-cylinder injection corrections

Good to know

• Repair difficulty: hard
• It affects emissions.

What each character of P21EA means

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

Frequently asked questions

Can I keep driving with code P21EA?

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 P21EA?

The most common causes are: cylinder 8 B injector wiring chafed through to ground; water or corrosion in the cylinder 8 injector plug; injector shorted to its body.

Related codes

• P21EBCylinder 8 Injector B Circuit High
• P21D6Cylinder 8 Injector B Circuit/Open
• P0282Cylinder 8 Injector A Circuit Low
• P21E8Cylinder 7 Injector B Circuit Low
• P21ECCylinder 9 Injector B Circuit Low
• P0175System Too Rich Bank 2
• P0308Cylinder 8 Misfire Detected

Sources

• gsi.ext.gm.com: 19OBDG03A Diagnostics
• fordservicecontent.com: OBD Operations Summary Gasoline 2020 2023
• mitsubishitechinfo.com: M11311510A007000USA

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.