P21E5: Cylinder 5 Injector B Circuit High

P21E5 means the cylinder 5 B injector circuit is pulled toward supply voltage. GM documents it for the LT5 V8 of the 2019 Corvette ZR1: the FICM looks at the low side of that injector while its driver is off and treats 0.5 Ohm or less toward power as a short. The test needs a running engine and at least 11 V at the powertrain relay, runs continuously and sets a Type A fault. A low side held at supply potential can never be switched to ground, so the injector stays closed. On this engine the port injectors were added mainly to supply extra fuel under boost, so a dead unit tends to show at high load, where cylinder 5 may run lean. The low-side counterpart is P21E4; the A injector of the same cylinder reports P0274 for the same fault type.

Cylinder 5 is numbered according to the manufacturer: check your engine's manual before working on it.

Symptoms

• Check engine light on
• Cylinder 5 lean or hesitant at full load
• Part-load driving often feels normal

Most likely causes

• Low-side wire of the cylinder 5 B injector shorted to a supply wire
• Supply and control wire of the injector bridged in the harness
• Injector coil shorted across its terminals
• Damaged output stage in the injection control module

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. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
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 P21E5 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 1: Air and fuel
• E5: Specific fault in that system

Frequently asked questions

Can I keep driving with code P21E5?

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 P21E5?

The most common causes are: low-side wire of the cylinder 5 B injector shorted to a supply wire; supply and control wire of the injector bridged in the harness; injector coil shorted across its terminals.

Related codes

• P21E4Cylinder 5 Injector B Circuit Low
• P21D3Cylinder 5 Injector B Circuit/Open
• P0274Cylinder 5 Injector A Circuit High
• P21E3Cylinder 4 Injector B Circuit High
• P21E7Cylinder 6 Injector B Circuit High
• P0171System Too Lean Bank 1
• P0305Cylinder 5 Misfire Detected

Sources

• gsi.ext.gm.com: 19OBDG03A Diagnostics
• lsxmag.com: inside corvette lt5 engine
• law.cornell.edu: 13 CCR 1968.2

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.