P256F code meaning
A/C Request B Circuit Range/Performance
What P256F means
P256F is the plausibility fault of a second A/C request input, B. Its wiring checks out, yet the engine module finds the state or timing illogical, for instance a request present while the first input and the climate controller say no cooling is wanted, or one that flickers instead of holding steady. Why a vehicle has two request inputs is up to each maker; a rear evaporator, a second compressor stage or a redundant cross-check line are plausible reasons. No maker documents P256F publicly. The legal basis is CARB's A/C component monitoring, which also covers A/C parts used as inputs to other diagnostics. Networked designs like the 2011 Saab 9-5, which take the request over the data bus, report trouble as communication codes instead. P2522 is the general fault on B, P255F the matching test on A.
P256F at a glance
- Check engine lightUsually not
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P256F
- Rear or second-stage cooling unreliable
- Idle dips or surges with A/C operation
Common causes of P256F
- PossibleClimate control logic sends inconsistent B request
- PossibleIntermittent connection on the B request line
- Less likelyFault in a second evaporator or compressor stage control
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Ac request input bHvac module
What each part of P256F means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 6F | The exact fault in that area. |
What to do next
- Note P256F 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 P256F
What does P256F mean?
P256F means "A/C Request B Circuit Range/Performance". P256F is the plausibility fault of a second A/C request input, B. It is a generic code, so it means the same on every make.
Is it safe to drive with P256F?
P256F does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P256F fail an emissions test?
Yes, it can. P256F 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 P256F to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P256F 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.