Cylinder 4 Injector Circuit High
The P0271 code indicates that the powertrain control module (PCM) has detected a high voltage or resistance in the electrical circuit for the fuel injector on cylinder 4. This can be caused by a faulty injector, wiring issues, or a problem with the PCM itself. The injector circuit is monitored for proper voltage and current; when the signal is out of range, the code is set.
1. Most Common Causes
- Faulty fuel injector on cylinder 4
- Short to voltage in the injector wiring or connector
- Open or high resistance in the injector circuit
- Corroded or damaged injector connector
- Failed PCM (rare)
2. Symptoms You Will Notice
- Engine misfire on cylinder 4
- Rough idle or hesitation
- Check Engine Light illuminated
- Decreased fuel economy
- Possible engine knocking
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for other related codes.
Step 2: Visually inspect the injector wiring and connector for damage, corrosion, or loose connections.
Step 3: Measure resistance of the cylinder 4 injector; compare to specifications (typically 12-16 ohms).
Step 4: Check for voltage at the injector connector with the engine running; should be battery voltage with the key on.
Step 5: Perform a injector balance test or swap injectors to isolate the issue.
Step 6: If wiring and injector are good, test the PCM output circuit.
4. 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. 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 the cause. Replacing a fuel injector can cost $100-$200, while wiring repairs may be less.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.