P21E6: Cylinder 6 Injector B Circuit Low

P21E6 reports that the B injector circuit of cylinder 6 has found a path to ground. In GM's 2019 tables for the Corvette ZR1 LT5, cylinder 6 is the third position on the right bank, which GM counts as bank 2. The FICM samples the switched-off low side every 100 ms and needs 20 bad readings out of 25, so a solid fault is confirmed within about two and a half seconds; the limit is 0.5 Ohm or less toward ground, Type A. A ground on the low side completes the injector circuit whenever its feed is live, so fuel can enter cylinder 6 without a command. Typical traces are a rich bank 2, fuel-wetted spark plug on that cylinder and fuel trims at their lean limit. P21E7 is the high fault of the same injector, P0276 the low fault of the A injector.

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

Symptoms

• Check engine light on
• Rich condition on bank 2, possibly fuel smell
• Fouled spark plug or misfire on cylinder 6

Most likely causes

• Cylinder 6 B injector harness chafed against engine metal
• Internal short to ground inside the injector
• Injection control module output stuck low

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 P21E6 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 1: Air and fuel
• E6: Specific fault in that system

Frequently asked questions

Can I keep driving with code P21E6?

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 P21E6?

The most common causes are: cylinder 6 B injector harness chafed against engine metal; internal short to ground inside the injector; injection control module output stuck low.

Related codes

• P21E7Cylinder 6 Injector B Circuit High
• P21D4Cylinder 6 Injector B Circuit/Open
• P0276Cylinder 6 Injector A Circuit Low
• P21E4Cylinder 5 Injector B Circuit Low
• P21E8Cylinder 7 Injector B Circuit Low
• P0175System Too Rich Bank 2
• P0306Cylinder 6 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.