P236B code meaning
Cylinder 12 Pressure Too Low
Powertrain system Generic code P23xx codes Check engine light
What P236B means
P236B reports that cylinder 12 builds too little combustion pressure while its sensor circuit itself is in order. No manufacturer documents the code, because no V12 or W12 with cylinder pressure measurement has been made public. A weak peak means this cylinder lacks air, fuel or sealing: a valve that does not close fully, a worn ring pack, a head gasket leaking towards a neighbour, or an injector delivering too little. Where cylinders are numbered bank by bank, 12 shares its bank with 7 to 11, so a compression test across that whole bank is worthwhile. A gas leak past the sealing element of the pressure glow plug also lowers the value. Rough idle and the misfire code P0312 often come with it; P236C is the deviation in the other direction.
P236B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyHard
- Typical labor1 to 10 hours
- Clears after repairAfter a drive cycle
Symptoms of P236B
- Check engine light on
- Rough idle and vibration
- Misfire code for cylinder 12 stored as well
Common causes of P236B
- PossibleIntake or exhaust valve of cylinder 12 not sealing
- PossibleWorn piston rings or head gasket leak
- PossibleInjector delivering too little fuel
- Less likelyGas leaking past the glow plug seal
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cylinder pressure sensor glow plugSensor wiringEngine control moduleFuel injector
What each part of P236B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 3 | Area: ignition system or misfire. |
| 6B | The exact fault in that area. |
What to do next
- Note P236B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P236B
What does P236B mean?
P236B means "Cylinder 12 Pressure Too Low". P236B reports that cylinder 12 builds too little combustion pressure while its sensor circuit itself is in order. It is a generic code, so it means the same on every make.
Is it safe to drive with P236B?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P236B fail an emissions test?
Yes, it can. P236B is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P236B to fix?
Difficulty: hard. A typical repair takes 1 to 10 hours of work. This is a job for a workshop.
Will P236B clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.