P0278 OBD-II Trouble Code: Cylinder 6 Contribution/Balance Fault

check engine light

P0278 code definition

The P0278 code represents an abnormal amount of voltage being detected in the vehicle’s fuel injector circuit.

What the P0278 code means

The P0278 code is stored when the PCM detects an amount of voltage in the fuel injector circuit that is outside of the manufacturer’s specifications. This code only applies to V6 vehicles. Voltage variations that exceed 10% of the manufacturer’s specified voltage will cause the P0278 code to get stored in the PCM as well as the Check Engine light to turn on.

What causes the P0278 code?

The main cause of the P0278 is actually wildlife. As the top of the engine tends to be quite warm, it attracts small animals looking for a heated place to rest in the winter. While enjoying the shelter provided by your vehicle, though, they often gnaw through the wiring in front of them.

Other reasons your PCM has stored a P0278 code include:

  • A clogged fuel injector
  • A faulty fuel injector
  • A faulty fuel injector driver within the PCM
  • Loose or corroded electrical wiring
  • Loose or corroded connector faces

What are the symptoms of the P0278 code?

There are actually a number of different symptoms that may accompany this code, but each is fairly different from the other. The abnormal voltage in one of your vehicle’s fuel injectors will definitely lead to reduced performance. Trying to accelerate may still be possible, but it will probably be quite choppy. When your vehicle is idling, it could make a skipping sound. The vehicle may even vibrate. If you check the RPMs, you might notice that they don’t remain consistent even though your car is sitting idle. Some people have even reported that their engine misfired.

How does a mechanic diagnose the P0278 code?

The mechanic will begin by checking scanning for the code and then assessing the transmission. They’ll go through each cylinder to look for signs that a wire or connector that has been compromised. If they don’t find any electrical issues that need to be repaired, the mechanic will move onto using an ohmmeter to test for a consistent power supply to the vehicle’s fuel injectors. Finally, they’ll clear the code and do a short test drive to see if P0278 returns or if the issue may be an intermittent problem.

Common mistakes when diagnosing the P0278 code

This code could be stored because your PCM actually failed, meaning there’s nothing wrong with your fuel injectors or their voltage. However, please keep in mind that this is actually extremely rare. A mechanic should exhaust every other possibility before dedicating time and resources to replacing the PCM.

How serious is the P0278 code?

Your life isn’t in danger because your vehicle has a P0278 code, but you’ll still want to get it in front of a professional mechanic right away. If your engine backfires, the repairs necessary could be very expensive. Even a choppy acceleration is nothing you want to experience on a regular basis. Aside from how uncomfortable it is, you’re also going to lose a lot of money on how poor your fuel efficiency is.

What repairs can fix the P0278 code?

Your mechanic will most likely do one of the following to get you back on the road:

  • Usually, wires or other electronic components in the affected fuel injector simply need to be replaced
  • The fuse panel – or at least some of its connectors – may need to be replaced
  • Fuel injectors may need to be replaced (possibly with O-rings)
  • Impaired fuel injectors will need their spray pattern fixed
  • In very rare cases, the PCM will need to be replaced

Additional comments for consideration regarding the P0278 code

If the mechanic finds that P0278 was caused by a critter, here are some tips for deterring squirrels from making your car their home. Hopefully, they’ll help prevent this problem in the future.

Need help with a P0278 code?

YourMechanic employs certified mobile mechanics who can not only help you with a P0278 code, but also meet you at your home or place of work. To get your quote and schedule an appointment, either call us at 1-800-701-6230 or complete this online form.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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