P0296: Cylinder 12 Contribution/Balance

What does P0296 mean?

P0296 comes from the cylinder balance control of common-rail diesels: the engine module measures the crankshaft acceleration of each cylinder's power stroke, compares it with the average and gives a deviating cylinder more or less fuel. The code sets when the correction for cylinder 12 reaches its limit and the cylinder still does not keep up – GM at 95 % of a limit of about ±12–17 mm³ for 30 s, Ford above 90 % of the allowed 3.5–15 mg per stroke for 7.5 s; GM needs two trips. The code does not say whether there is too much or too little fuel – the correction value for cylinder 12 shows the direction: strongly negative means a leaking injector, strongly positive a weak injector or low compression. Cylinder 12 only exists on diesels with twelve cylinders; GM and Ford documents stop at cylinder 8, so the description follows CARB and the siblings.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Rough idle, shaking or knocking
• Loss of power or smoke
• Higher consumption, poor cold start

Common causes

• High Injector of cylinder 12 worn, coked or leaking
• Medium Engine software outdated or diagnosis too sensitive
• Medium Injector correction codes not or wrongly programmed after replacement
• Medium Low compression on cylinder 12 (valve, rings, injector seal)
• Low Crankshaft sensor or tone wheel learning faulty, dual-mass flywheel

Likelihood is a general estimate across vehicles; your make and model may differ.