P25F6AIR System B
- 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
- 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.
- What you may notice
- 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
- Likely causes
- 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
- RareFaulty pump relay, fuse or wiring of system B
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €80 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.