P236ACylinder 12 Pressure Sensor Circuit Intermittent/Erratic
- 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
- P236A covers brief, irregular disturbances of the cylinder 12 pressure signal – faults that come and go without settling into a lasting low or high state. Its model is the Saab 9-5 diesel code P0399, which responds as soon as the signal stays outside its band longer than 0.2 s. No manufacturer publishes P236A itself, since no twelve-cylinder engine with pressure glow plugs is documented. Volkswagen's 2014 bulletin for 2.0 TDI engines gives a practical routine for such cases: watch the maximum pressure value of every cylinder while flexing harness and connectors, and swap the suspect glow plug with one from a neighbouring cylinder. If the fault follows the plug, the plug is bad; if not, the harness is. Up to two drive cycles may pass before the lamp returns.
- What you may notice
- Warning lamp that switches on and off over several days
- Pressure value of cylinder 12 jumps when the harness is moved
- Likely causes
- LikelyLoose or corroded terminal in the plug connector
- PossibleHarness rubbing through under engine vibration
- PossibleGlow plug sensor with intermittent internal fault
- 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: €40 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.