Capteur de pression cylindre défectueux

The in-cylinder sensor that watches combustion directly, failed or drifting — and on the engines that carry one, deliberately the last name on most of its own codes' lists, because the wiring to a sensor screwed into a cylinder head fails far more often than the sensor sealed inside it.

When it genuinely is the sensor, the failure is usually drift: the element ages in the pressure and heat it measures, and the reading wanders rather than dying. The engine's own cross-check convicts it cleanly — with fuel cut on overrun, all cylinders trace near-identical pure compression, so one sensor disagreeing with its siblings under those conditions has identified itself. The exception worth knowing: a pressure trace too smooth to be real (the Variation Low codes) inverts the usual order and puts this sensor first, since healthy combustion always varies a little and only a dead element reports otherwise.

On most diesels the sensor is integrated into the glow plug, which sets the honest price of replacement — a pressure-sensing glow plug, not a plain one.