P0278Generic code

P0278 Code: Cylinder 6 Contribution/Balance

The P0278 code means cylinder 6 is contributing less (or more) power than the other cylinders. It is typical of diesel engines and points to a worn, clogged or leaking injector, or to a compression problem. You can drive with caution for a short time, but a cylinder that is not pulling its weight wears the engine faster.

Severity
Medium
Can I keep driving?
Yes, but with caution
Estimated cost
$20 to $800
Difficulty
Medium
System
Fuel Injection
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0278 code means

The computer compares how much each cylinder accelerates the crankshaft. On diesels it corrects the amount of fuel each injector delivers so the engine runs balanced (per-cylinder fuel quantity correction). If cylinder 6 needs a correction outside the allowed limit, or keeps contributing differently from the rest, the computer stores the P0278 code.

On diesels, each cylinder contribution can also be checked with a return flow test: you disconnect the injector return lines and collect the fuel from each one in a container for a fixed time with the engine idling. An injector that returns much more than the others has an internal leak and is not spraying cylinder 6 properly.

Cylinder numbering depends on the manufacturer. On most inline engines, cylinder 1 is the one closest to the timing belt or chain. On V engines, the odd and even cylinders are usually on different banks. Confirm the numbering in the service manual before you take anything apart.

P0278 code symptoms

  • Check engine light on.
  • Engine shaking or a rough idle.
  • Loss of power.
  • Black or white smoke (diesel) or misfires (gas engine).
  • High fuel use or a smell of fuel.

Likely causes of the P0278 code

  1. Worn or clogged injector 6. The most common cause on high-mileage diesels.
  2. Injector 6 leaking or dripping. It delivers too much fuel and produces smoke.
  3. Low compression in that cylinder. Valves, piston rings or the head gasket.
  4. Contaminated fuel that damages the injectors.
  5. Injector codes not programmed after an injector was replaced without being coded (common on diesels).

How to diagnose the P0278 code step by step

  1. Confirm the cylinder with the scan tool (misfire counters, or per-cylinder fuel quantity corrections on a diesel).
  2. Read the fuel quantity corrections for all the injectors at hot idle. The affected one is usually far apart from the others.
  3. Run the injector return flow test (diesel). An injector with much more return flow than the others has an internal leak.
  4. Measure the compression of the cylinder to rule out a mechanical problem.
  5. If an injector was replaced, check that its calibration code was programmed (IMA, QR or C2I depending on the brand).
  6. Clear the codes and recreate the condition to confirm the repair.

How to fix the P0278 code

  • Clean or replace the affected injector (on a diesel, at an injection specialist).
  • Program the new injector into the computer when the manufacturer requires it.
  • Repair the mechanical cause if the compression is low.
  • Change the fuel filter and check for water in the fuel.
  • Clear the codes and verify on a road test.

Technical reference data

  • High-impedance gasoline injector: 11 to 18 ohms.
  • Low-impedance injector: 2 to 5 ohms.
  • Typical supply: 12 V from a relay or the computer. The computer switches the ground to open the injector.
  • Piezo common rail diesel injectors are not tested with an ohmmeter the same way. Follow the manufacturer procedure.
  • Typical diesel quantity correction: within +/-2 to +/-3 mm³ per injection.
  • These values are for orientation only. Check the manufacturer data for your engine.

Brand-specific notes

On common rail diesels (Toyota D-4D, Nissan dCi, Ford TDCi, Volkswagen TDI, Hyundai CRDi), the injectors carry a calibration code that must be written into the computer when they are replaced. Without that step, contribution and balance codes like the P0278 code show up.

Frequently asked questions about P0278

Can I drive with a P0278 code?
With caution and only for a short time. A cylinder that is not contributing makes the engine shake and increases wear.
Which cylinder is number 6?
Cylinder numbering depends on the manufacturer. On most inline engines, cylinder 1 is the one closest to the timing belt or chain. On V engines, the odd and even cylinders are usually on different banks. Confirm the numbering in the service manual before you take anything apart.
Does the injector have to be replaced?
Often yes, but try a cleaning first and check the compression and the injector coding.
How much does it cost to fix P0278?
Between $20 and $600 on a gas engine. On a diesel, an injector can cost $150 to $800 plus the coding.
What does the P0278 code mean?
It is a generic OBD2 code that means cylinder 6 is contributing more or less power than the other cylinders. On a diesel it usually points to the cylinder 6 injector.
Will a P0278 code clear itself?
Rarely. The cause is a worn injector or a mechanical problem, and those do not heal on their own. The light may go out if the fault is intermittent, but the code returns once the condition comes back.

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