Cylinder 4 Injector Circuit High
The P0271 code indicates that the Engine Control Module (ECM) has detected a high voltage or resistance in the electrical circuit for the fuel injector on cylinder 4. This typically means the injector driver circuit is seeing higher than normal voltage, often due to a short to power, a faulty injector, or a wiring issue. The ECM monitors the injector circuit for proper voltage and current; when the voltage is too high, it sets this code to protect the injector and ECM.
01. Most Common Causes
- Short to power in the injector wiring or connector
- Faulty fuel injector (internal short)
- Corroded or damaged injector connector
- ECM internal fault (rare)
02. Symptoms You Will Notice
- Engine misfire on cylinder 4
- Rough idle or hesitation
- Check Engine Light illuminated
- Possible fuel odor or poor fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and note freeze frame data.
Step 2: Visually inspect the injector connector and wiring for damage, corrosion, or shorts.
Step 3: Measure resistance of cylinder 4 injector; compare to specification (typically 12-16 ohms).
Step 4: Check for voltage at the injector connector with key on; should be battery voltage on one pin.
Step 5: Perform a continuity test from the injector connector to the ECM to check for shorts to power or ground.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can cause engine misfire, reduced performance, and potential damage to the catalytic converter or ECM. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on whether it's a simple wiring fix or injector replacement. Injector replacement can cost more if needed.