Engine

P0296 — Cylinder 12 Contribution/Balance Fault

Severity: medium Drive with care, to a shop

What P0296 means

The engine control module constantly compares how evenly each cylinder contributes to engine output, usually by watching crankshaft speed changes. P0296 means cylinder 12 is producing noticeably less power than the others. The cause can be poor fuel delivery, weak spark or lost compression. This code applies to 12-cylinder engines.

Symptoms

  • Check Engine light on
  • Rough idle
  • Reduced power and sluggish acceleration
  • Noticeable engine vibration
  • Worse fuel economy
  • Possible hesitation under load

Possible causes

  1. Faulty fuel injector on cylinder 12
  2. Open, short or corroded wiring or connector in the injector circuit
  3. Failed ignition coil or spark plug on cylinder 12
  4. Mechanical problem in the cylinder: low compression, burnt valve, worn rings
  5. Vacuum leak or fuel supply problem affecting one bank
  6. Rarely, an ECM fault or software error

How to diagnose

  1. Read all codes and freeze frame data and look for other misfire codes (P0300-P0312).
  2. Identify which physical cylinder is number 12 for the specific engine.
  3. Inspect the injector and coil wiring and connectors for damage, oil and corrosion.
  4. Check the spark plug and coil on cylinder 12; swap them with a good cylinder and see if the fault follows.
  5. Test the injector: coil resistance, driver pulse, operation sound and flow.
  6. Run a compression or cylinder leak-down test.
  7. Check fuel pressure and look for vacuum leaks.
  8. If everything is fine, check ECM power and ground and look for software updates.

Common fixes

  • Replace or clean the faulty fuel injector
  • Repair the damaged wiring or connector
  • Replace the spark plug or ignition coil on cylinder 12
  • Repair the internal engine problem (valves, rings, cylinder head)
  • Update ECM software or replace the ECM (rare)

Questions and answers

What does P0296 mean?

The engine computer detected that cylinder 12 is working weaker than the rest. Most often the injector, its circuit or ignition is at fault, less often an internal engine problem.

Can I drive with code P0296?

Only carefully and briefly, to get to a shop. If the check engine light flashes or the engine shakes badly, stop to avoid damaging the catalytic converter and engine.

How do I tell an electrical cause from a mechanical one?

Swap the coil or injector with one from a neighboring cylinder. If the fault moves, that part is bad. If it stays, do a compression test.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.