OBD-II Code P0274 — What It Means & How to Fix It

What Does This Error Mean?

P0274 means the fuel injector circuit for Cylinder 5 is reading a high voltage or current signal. The ECM controls each injector by switching its ground circuit on and off. When the Cylinder 5 injector circuit reads higher than expected, a short to voltage or internal injector fault is likely. A stuck-open injector scenario caused by a high circuit fault will flood Cylinder 5 with excess fuel. Symptoms include a strong fuel smell, rough running, black exhaust smoke, and potentially a Cylinder 5 misfire code.

Affected Models

All vehicles 1996+ with 5 or more cylinders
Common in V6, V8, and V10 trucks and SUVs
Common after wiring harness repairs done incorrectly
More common on vehicles with corroded or heat-damaged injector wiring

Common Causes

Short to voltage in the Cylinder 5 injector control wire causing an elevated signal
Faulty Cylinder 5 injector with an internal short causing abnormal circuit behavior
Wiring harness damage where the Cylinder 5 injector wire contacts a 12V source
Incorrect injector installed with a mismatched resistance specification
ECM injector driver for Cylinder 5 stuck in a high-output state due to internal failure

How to Fix It

Inspect the Cylinder 5 injector connector and the entire wiring run. Look specifically for any wires that appear bare, melted, or touching power sources like battery cables, alternator wiring, or the fuse box feeds.

A short to voltage is often caused by a wire whose insulation has worn off where it passes near a sharp bracket or hot surface.
Unplug the Cylinder 5 injector. With the key in the ON position (engine off), use a multimeter to measure voltage on both terminals of the harness-side connector. The power terminal should show battery voltage (~12V). The control terminal should show near zero volts when the injector is unplugged and the ECM is not commanding it.

If both terminals show 12V, the control wire has a short to voltage somewhere between the connector and the ECM.
Test the injector's internal resistance. Set a multimeter to ohms and probe the two terminals on the injector itself (not the harness connector). Compare the reading to spec — most injectors are 10–18 ohms. A reading near zero indicates an internal short; the injector must be replaced.

Never reinstall an injector that shows near-zero resistance — it will stay on continuously and flood the cylinder.
Verify the injector part number if recent injector work was done. Installing a low-impedance racing injector in a standard high-impedance circuit causes exactly this type of 'high circuit' code. The ECM will see the incorrect resistance as a circuit fault.

Always confirm injector part numbers match OEM specifications for your vehicle's engine.
After fixing any wiring or injector issues, clear the code and drive to confirm the repair. If P0274 returns with no identifiable wiring or injector fault, have a professional test the ECM's Cylinder 5 driver circuit with a scope or breakout box before replacing the ECM.

ECM replacement without proper diagnosis is one of the most common — and expensive — misdiagnoses in automotive repair.

When to Call a Professional

A high-circuit injector fault that causes the injector to stay open is a serious problem. Fuel flooding into Cylinder 5 can wash oil off the cylinder walls and cause accelerated wear. If you smell raw fuel strongly from the exhaust or notice black smoke, stop driving and get this inspected quickly. Don't attempt to repair ECM internals yourself — have a certified technician test the module.

Frequently Asked Questions

What is the difference between P0273 and P0274?

Both codes affect Cylinder 5's injector circuit. P0273 means the signal is too LOW — suggesting a break, bad connector, or open-circuit injector. P0274 means the signal is too HIGH — suggesting a short to voltage or a stuck/shorted injector.

Can a high circuit injector fault cause engine damage?

Yes, if the injector stays open continuously. Excess fuel in the cylinder washes away the oil film on the cylinder walls, accelerating wear on the rings and bore. In extreme cases, liquid fuel in the cylinder can cause hydraulic lock — a situation that can bend connecting rods instantly.

How much does it cost to fix P0274?

Wiring repair: $100–$300. Injector replacement: $150–$400 installed. ECM repair or replacement: $300–$1,200+.