P236DCylinder 12 Pressure Variation Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P236D is stored when the cylinder 12 pressure trace swings too little – the curve stays flatter than compression and combustion ought to make it. No manufacturer documents this code for a twelve-cylinder engine. In Saab's 9-5 diesel the comparable cylinder-1 code P039C exists in three sub-variants, 00, 01 and 02, a sign that the ECM tells apart several ways in which a signal can be too weak. The likely culprits sit in the sensor: in BorgWarner's design a flexible heater rod passes the pressure on to a measuring diaphragm, so carbon that grips the rod dampens the signal, and ageing circuitry in the head of the plug lowers its amplification. If compression itself were missing, P236B would be the more likely entry. Driving is normally unaffected.
- What you may notice
- Check engine light on
- Flat pressure curve for cylinder 12 in live data
- Likely causes
- LikelyCarbon deposits restricting the heater rod
- PossibleSensor electronics with reduced gain
- RareActual low compression in cylinder 12
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €100 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.