P0274 is a manufacturer-specific code (used by GM and others) indicating the powertrain control module detected excessive voltage in the cylinder 5 fuel injector circuit. This typically means the injector or its wiring is shorted to power, causing the injector to remain open or unable to operate properly.
The injector coil inside cylinder 5 has shorted internally, causing excessive current draw and triggering the high voltage fault.
The injector wiring harness is damaged, chafed, or melted, creating a direct short to battery voltage in the circuit.
The injector connector pins are corroded, oxidized, or contaminated, causing an anomalous high-voltage reading.
The injector circuit wire is pinched, rubbed through, or damaged at the connector or elsewhere in the engine harness.
The output transistor that drives cylinder 5's injector has failed internally (rare; less than 5% of cases).
Non-OEM fuel injectors, tuners, or wiring additions can create voltage anomalies the PCM interprets as a fault.
No. While the PCM can fail, it is responsible for fewer than 5% of P0274 cases. The far more common culprits are the injector itself, wiring issues, or connector problems.
Driving is not recommended. The cylinder 5 misfire can lead to catalytic converter damage from unburned fuel, and raw fuel entering the oil (if the injector is stuck open) can cause engine wear.
Costs vary widely: a wiring repair or connector cleaning may cost under $100, while a new OEM fuel injector plus labor can range from $150 to $400 depending on the vehicle.
Probably not. This is a common over-diagnosis. Always verify the injector, wiring, and connectors are ruled out first before considering PCM replacement, which should be a last resort after all other causes are eliminated.