What Does P0271 Mean?
The ECM has detected an excessively high voltage or current in the cylinder 4 fuel injector circuit. This means the injector driver circuit is seeing higher-than-expected electrical values, which could be caused by a shorted injector, wiring fault, or ECM driver issue. The driver may notice rough running, excessive smoke from cylinder 4 overfueling, or engine knock.
Common Causes
35%
Short to battery voltage in the cylinder 4 injector wiring
30%
Cylinder 4 fuel injector with internal electrical short (low resistance)
15%
Corroded or damaged connector at the cylinder 4 injector
12%
ECM injector driver circuit fault for cylinder 4
8%
Wiring crossed or shorted between cylinder 4 and adjacent injector circuits
Diagnostic Steps
1
Disconnect the cylinder 4 injector and measure its resistance — compare to manufacturer specs (typically 0.5-1.5 ohms for piezo diesel, 11-16 ohms for gasoline). A significantly low reading indicates an internal short.
2
With the injector disconnected, check the harness side for shorts to battery voltage by measuring from each pin to B+ — any continuity indicates a wiring short that must be traced and repaired.
3
Inspect the cylinder 4 injector connector for signs of heat damage, fuel contamination, moisture intrusion, or corroded terminals that could alter circuit resistance.
4
Use a current clamp on the cylinder 4 injector wire to monitor the actual current draw — compare the peak and hold current profile to a known-good cylinder.
5
Swap the cylinder 4 injector with another cylinder, clear codes, and run the engine — if the high circuit code follows the injector, replace it; if it stays at position 4, the wiring or ECM driver is at fault.
Estimated Repair Cost
$100 - $800
Parts + labor, varies by vehicle and location
The ECM has detected an excessively high voltage or current in the cylinder 4 fuel injector circuit. This means the injector driver circuit is seeing higher-than-expected electrical values, which could be caused by a shorted injector, wiring fault, or ECM driver issue. The driver may notice rough ru...
The most common cause of P0271 (Cylinder 4 Injector Circuit High) is: Short to battery voltage in the cylinder 4 injector wiring
Typical repair costs for P0271 range from $100 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A high injector circuit can cause overfueling and potential engine knock or catalytic converter damage. Avoid sustained high-load driving and have it repaired soon to prevent secondary damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0271 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel Injection System
Difficulty
Type
Generic (SAE)
Recommended Tools
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