P236F: Cylinder 12 Combustion Performance
The closed-loop combustion controller reports that combustion performance on cylinder 12 is below the calibrated quality metric. Computed from the cylinder pressure trace — IMEP (indicated mean effective pressure), CA50 (50% mass burnt angle) or peak pressure deviates from the model.
What P236F means
P236F is a generic OBD-II powertrain code in the misfire & ignition group. In plain English: the signal is within electrical limits but doesn’t make sense compared with other readings, so the part or system isn’t performing as expected.
- Check engine light
- Usually on
- Emissions-related
- Yes — can fail inspection
- Limp mode possible
- Not typical
- Drive cycle to clear
- Not required
Get it fixed
Post this code once and get quotes from local mechanics. Free to post.
Makes the repair and parts links below specific to your car. Kept in this browser only.
Common causes
- 01Mean effective pressure outside modelMost likely
- 02Gateway module routing CAN messages incorrectlyLess likely
- 03CAN terminating resistor (120 Ω) drifted out of specLess likely
Can I drive with P236F?
Usually yes, for a short time.
The car will often drive normally, but get it diagnosed soon. Left alone it can raise fuel use and emissions and will fail an OBD inspection. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
Why we rate it moderate
- Turns on the check engine light
- Emissions-related: will usually fail an OBD inspection
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose P236F
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P236F. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Check for related codes first
Look for P2365, P235B, P2351, P03E4. Related codes often share a cause; a circuit or sensor code usually needs fixing before a performance code like this one.
- 3
Check module power, ground and the data bus
Confirm the module named in the code has battery voltage, ignition feed and a good ground. With the battery disconnected, a healthy CAN bus usually measures about 60 ohms between CAN-High and CAN-Low at the OBD port. Inspect connectors for corrosion and pushed-out pins.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Mean effective pressure outside model; gateway module routing CAN messages incorrectly; CAN terminating resistor (120 Ω) drifted out of spec. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
P236F repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Hard
- Good DIY job?
- Usually a shop job
Involved testing or major parts. Most owners use a shop.
Parts and systems involved
- Cylinder 12 combustion
- Cylinder pressure sensor 12
P236F FAQ
What does P236F mean?
P236F means “Cylinder 12 Combustion Performance”. The closed-loop combustion controller reports that combustion performance on cylinder 12 is below the calibrated quality metric. Computed from the cylinder pressure trace — IMEP (indicated mean effective pressure), CA50 (50% mass burnt angle) or peak pressure deviates from the model.
Is P236F serious? Can I keep driving?
We rate P236F as moderate severity. Usually yes, for a short time. The car will often drive normally, but get it diagnosed soon. Left alone it can raise fuel use and emissions and will fail an OBD inspection. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
What causes P236F?
The most common causes, from most to least likely: Mean effective pressure outside model; Gateway module routing CAN messages incorrectly; CAN terminating resistor (120 Ω) drifted out of spec. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P236F?
Typical labor is about $190–$750 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix P236F myself?
DIY difficulty is hard. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will P236F clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.