P25F6 code meaning
AIR System B
Powertrain system Generic code P25xx codes Check engine light
What P25F6 means
P25F6 is the overall monitor for a second secondary air injection system, lettered B, on engines with two separately controlled air delivery paths; system A reports through P0410 and P0411. During warm-up after a cold start a pump pushes fresh air into the exhaust, so leftover HC and CO burn off and the catalyst lights off sooner. CARB wants the complete delivery chain monitored, every switching valve included, and with separate paths the flow to each bank. No manufacturer documents P25F6 publicly; Toyota's 4.7 L 2UZ-FE V8 shows such a layout with one switching valve per bank but stores mostly its own codes for it. P25F6 is the general fault of system B, P25F7 the narrower flow complaint. The driver sees the MIL and fails an emissions test, while the car normally drives as usual.
P25F6 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P25F6
- MIL on, usually after a cold start
- Secondary air readiness monitor not complete, emissions test failed
- Unusual whining or no pump noise during the first minute after a cold start
Common causes of P25F6
- Most likelySecondary air pump of system B worn, seized or water-damaged
- PossibleSwitching or check valve of system B stuck, often after debris from the pump
- PossibleCracked, loose or disconnected air hose or vacuum line
- Less likelyFaulty pump relay, fuse or wiring of system B
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Air pump bAir check valveAir pipes
What each part of P25F6 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. |
| F6 | The exact fault in that area. |
What to do next
- Note P25F6 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 P25F6
What does P25F6 mean?
P25F6 means "AIR System B". P25F6 is the overall monitor for a second secondary air injection system, lettered B, on engines with two separately controlled air delivery paths; system A reports through P0410 and P0411. It is a generic code, so it means the same on every make.
Is it safe to drive with P25F6?
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 P25F6 fail an emissions test?
Yes, it can. P25F6 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 P25F6 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P25F6 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.