P0296: Cylinder 12 is not contributing as much power as the other cylinders
Cylinder 12 contribution/balance fault
Severity: Severity not verified — if the car runs badly, have it inspected
The two sources that define this code do not rate how urgent it is, so the severity is not verified. A cylinder that is not pulling its weight can make the engine run rough, so have it checked.
P0296 in short
P0296 means the engine computer found that cylinder 12 is not adding its share of power compared with the other cylinders. A dirty or faulty fuel injector is the most common cause, then mechanical wear such as burnt valves or worn rings. A shop can confirm with injector and compression checks.
The engine computer compares how much each cylinder adds to crankshaft speed. When cylinder 12 adds noticeably less than the rest, it sets P0296. TroubleCodes.net describes this as the cylinder not delivering an adequate power impulse relative to the others.
The usual cause is the fuel injector for that cylinder, which can be dirty or clogged. TroubleCodes.net also lists mechanical wear (burnt valves, worn piston rings, a leaking head gasket) and, on diesels, an injector that was replaced without the required learning procedure.
Cylinder 12 only exists on engines with at least 12 cylinders, which in practice means large V12 and similar engines. The Delaware DMV code list gives the same title for P0296.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Dirty or faulty fuel injector on cylinder 12
Common general cause- Why it ranks here
- TroubleCodes.net names dirty fuel injectors as the leading cause of contribution/balance faults, from poor fuel, poor filtering or carbon buildup.
- What would change this
- Rises if the injector sounds or reads differently from its neighbours. Falls if injector checks are normal and compression is low.
Cause 2: Replaced diesel injector that was not learned to the computer
Possible — needs testing- Why it ranks here
- TroubleCodes.net says diesel injectors need a learning procedure after installation; it applies only if an injector was recently fitted.
- What would change this
- Rises if the code started right after injector work on a diesel. Falls on a petrol engine or with no recent injector work.
Cause 3: Mechanical fault in cylinder 12 (burnt valve, worn rings, head gasket)
Possible — needs testing- Why it ranks here
- TroubleCodes.net lists these as mechanical reasons one cylinder produces less power; they rank below the injector because they are found only after injector checks.
- What would change this
- Rises if compression or leakdown differs by more than about 10 percent from other cylinders. Falls if readings match.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Inspect the cylinder 12 injector connector and wiring for corrosion or water damage.
IfCorrosion or water in the connector
It meansPoor contact may be starving the injector.
IfConnector looks clean
It meansCompare the injector with its neighbours.
Step 2: Compare cylinder 12's injector waveform with a neighbouring cylinder using an oscilloscope, or listen to each injector with a mechanic's stethoscope.
Warning:Work near a running engine with moving belts, hot parts and fuel under pressure. Leave this to a shop.
IfCylinder's injector signal or sound differs from the others
It meansThe injector is the likely fault.
IfInjector signal and sound match the others
It meansTest the cylinder mechanically.
Step 3: Run a compression test and a leakdown test on cylinder 12 and compare it with the other cylinders.
Warning:Removing plugs or injectors on a warm engine can burn you, and cranking with fuel or ignition connected can spray fuel or shock you. Leave this to a shop.
IfReadings vary by more than about 10 percent or leakdown is high
It meansThe cylinder has a mechanical fault.
Points to: Mechanical fault in cylinder 12 (burnt valve, worn rings, head gasket)
IfReadings are even
It meansInjector or software problem remains; seek professional diagnosis.
Symptoms
- Rough idle
- Reduced engine performance
- Worse fuel economy
- No noticeable symptoms in some cases
How to fix
On your vehicle
We don't have reviewed vehicle-specific evidence for P0296 yet. The causes and tests above apply across vehicles.
Related codes
No curated relationships for P0296 yet.
Sources and review
- P0296 – Cylinder 12 Contribution/Balance Fault
- On-Board Diagnostic Trouble Codes (generic code title list)
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error