P0271 – Cylinder 1-8 Injector Circuit High

Understanding and Fixing OBD-II Code P0271

If your car's OBD-II system has logged a P0271 code, it indicates there is an issue with cylinder #4 contribution/balance. This code is triggered when the PCM detects that cylinder #4 is not producing the expected power output compared to the other cylinders.

Urgency and Severity

A P0271 code itself does not require immediately stopping driving, but it should be diagnosed and repaired promptly. Driving with a misfiring cylinder can cause:

• Rough running and poor performance
• Increased emissions
• Potential catalytic converter damage from unburned fuel

If the misfire is severe enough to cause significant shaking or power loss, pull over when safe and have the vehicle towed to avoid engine damage.

Code Specifics

The P0271 code is a generic powertrain code that applies to all makes and models of vehicles. The code definition is:

• P0271 – Cylinder 4 Injector Circuit High

Affected Components

The P0271 code implicates several components related to cylinder #4 fuel delivery:

• Fuel injector
• Injector wiring harness and connector
• Fuel injector control module (FICM)
• Powertrain control module (PCM)

Common Causes

Some of the most common causes for a P0271 code include:

1. Faulty or internally shorted fuel injector
2. Damaged wiring or connector to the injector
3. Malfunctioning fuel injector control module
4. Faulty powertrain control module

Diagnosis Steps

To pinpoint the root cause of a P0271 code, a mechanic should follow these steps:

1. Visually inspect the injector wiring harness and connector for damage.
2. Perform a resistance test on the fuel injector to check its function.
3. Use a scan tool to check communication with the FICM.
4. Test for power and ground at the FICM and PCM connectors.
5. If all other components check out, consider replacing the fuel injector.

Repair Solutions

Repairs for a P0271 code will depend on the diagnosed cause:

• Wiring issue – repair or replace damaged wiring and connector (cost varies)
• Faulty fuel injector – replace the cylinder 4 injector (cost: $120-$350)
• FICM failure – replace the fuel injection control module (cost varies)
• PCM failure – replace the powertrain control module (cost: $500-$1500)

Prevention and Maintenance

To help prevent a P0271 code from reoccurring:

• Follow recommended service intervals for fuel filter changes
• Use high quality fuel from Top Tier gas stations
• Address any fuel system leaks promptly
• Keep the fuel injectors clean with periodic fuel system service

Associated Codes

Other codes commonly seen with P0271 include:

• P0300 – Random/Multiple Cylinder Misfire
• P0304 – Cylinder 4 Misfire Detected

Key Takeaways

• P0271 indicates a problem with the cylinder 4 fuel injector circuit
• It can cause rough running, increased emissions, and catalytic converter damage
• Common causes are a faulty injector, wiring issues, or control module failures
• Diagnosis requires checking the injector, wiring, FICM and PCM
• Repair costs range from $120 for an injector to $1500 for a PCM
• Proper fuel system maintenance can help prevent the issue

By understanding code P0271, you can more quickly diagnose and repair cylinder 4 fuel injector circuit faults to restore engine performance. As always, if you are unsure about any repair, consult a professional mechanic.

Frequently Asked Questions About P0271

What does OBD-II code P0271 mean?

Code P0271 indicates that the powertrain control module (PCM) has detected a higher than expected voltage in the injector control circuit for cylinder #4. This suggests an issue with the wiring, connector, fuel injector, or PCM itself related to that specific cylinder.

How serious is a P0271 code?

A P0271 code can cause cylinder #4 to misfire, leading to rough running, poor acceleration, increased emissions, and potentially internal engine damage if left unaddressed. While it may not cause a no-start condition initially, it's important to diagnose and repair the underlying issue promptly.

What are the common symptoms of a P0271 code?

Typical symptoms you may notice with a P0271 code include:

• Check engine light illumination
• Rough idle or running
• Lack of power, especially under load
• Increased fuel consumption
• Difficulty starting the engine
• Smell of unburned fuel from exhaust

What are the likely causes of a P0271 code?

Some of the most common causes for a P0271 code are:

1. Faulty or internally shorted fuel injector on cylinder #4
2. Damaged wiring or connector for the cylinder #4 injector circuit
3. Malfunctioning fuel injector control module
4. Faulty PCM not properly controlling the injector

Can I drive with a P0271 code?

It's not advisable to continue driving with an active P0271 code for an extended period. The poor running condition and misfires can lead to unburned fuel entering the exhaust, which can damage the catalytic converter. It's best to address the issue as soon as possible.

How do I diagnose a P0271 code?

To properly diagnose a P0271 code, a technician should:

1. Visually inspect the wiring and connector condition
2. Perform a resistance and functionality test on the suspect fuel injector
3. Check for proper communication between the PCM and fuel injection control module
4. Verify PCM is not faulty and sending incorrect signals to the injector

Can a bad fuel injector cause a P0271 code?

Yes, a faulty fuel injector is one of the most common causes for a P0271 code. If the injector winding shorts internally, it can cause a higher than expected current draw and voltage in the circuit, triggering the code.

How much does it cost to fix a P0271 code?

The cost to repair a P0271 code can vary depending on the root cause:

• Fuel injector replacement: $120-$350
• Wiring harness repair: $50-$200
• Fuel injection control module: $400-$1200
• PCM replacement: $500-$1500
  Proper diagnosis is key to determining the most cost-effective repair.

Can a P0271 code clear itself?

In most cases, a P0271 code will not clear on its own even if the underlying issue is intermittent. The code will remain stored in the PCM's memory until it is cleared with a scan tool or the power is disconnected long enough to reset the keep alive memory.

Is a P0271 code specific to cylinder #4?

Yes, a P0271 code by definition is specific to a fault detected in the injector circuit for cylinder #4. Other cylinders may have similar codes if they experience a fault, such as P0261 for cylinder #1, P0264 for cylinder #2, P0267 for cylinder #3, etc.

Can a vacuum leak cause a P0271 code?

No, a vacuum leak alone would not likely cause a P0271 code, as this deals specifically with a high voltage condition in the injector circuit. However, a large vacuum leak can cause a lean running condition that might induce a misfire and possibly damage an injector.

Will a P0271 code always trigger a misfire code?

In most cases, a P0271 code will be accompanied by a cylinder #4 misfire code P0304. However, if the injector fault is intermittent or not severe enough, it may set the P0271 without yet triggering a detectable misfire code.

Can a P0271 code affect fuel economy?

Yes, any fault that causes incomplete combustion or cylinder misfire can negatively impact fuel economy. The PCM may try to compensate by running richer and wasting unburned fuel. Repairing the underlying issue should restore normal fuel efficiency.

What is the difference between an injector electrical fault and a clogged injector?

An electrical fault like a P0271 deals with the injector circuit and ability to properly actuate the injector solenoid. A clogged injector is a mechanical issue where deposits physically restrict the flow of fuel through the injector. Both can cause poor performance but require different testing methods.

How often should fuel injectors be replaced?

On most modern vehicles, the fuel injectors are not a regularly scheduled maintenance item. They are typically designed to last the lifetime of the engine. However, poor fuel quality, lack of maintenance, or manufacturing defects can cause premature injector failures that require replacement.

Can I replace just one fuel injector for a P0271 code?

In most cases, if a faulty injector is identified as the cause of a P0271 code, only that single injector needs to be replaced. However, if the engine has very high mileage or other injectors show signs of failure, some technicians recommend replacing them all as a set.

Should I use fuel injector cleaner additives to prevent a P0271 code?

Using a quality fuel injector cleaner periodically can help dissolve deposits and keep injectors working properly. However, once an injector has failed electrically and triggered a P0271, no additive will repair that internal fault. It will need to be replaced.

What are the most common P0271 code failures?

Based on industry data, the most common causes of a P0271 code that result in a diagnosed failure are:

1. Faulty fuel injector: 62%
2. Wiring/connector issue: 21%
3. Fuel injector control module: 13%
4. PCM failure: 4%

Is a P0271 code covered under warranty?

A P0271 code may be covered under the emissions control warranty, which is typically 2 years/24,000 miles minimum and up to 8 years/80,000 miles on some components. However, if the cause is determined to be a faulty fuel injector, it may only be covered under the shorter bumper-to-bumper warranty. Always check with your dealer for specific warranty information.

What are some other common codes that may appear with a P0271?

When diagnosing a P0271 code, it's not uncommon to also find other related codes that can help pinpoint the underlying problem, such as:

• P0300 Random/Multiple Cylinder Misfire
• P0304 Cylinder #4 Misfire
• P0204 Injector Circuit Malfunction – Cylinder #4
• P1271 Cylinder #4 Injector Circuit Malfunction
• P0172 Fuel Trim System Too Rich