P25F6: AIR System B
A general fault in the second secondary air injection (AIR) circuit. Detected by the O2 sensors which expect a lean swing during cold-start AIR pump operation but do not see one.
What P25F6 means
P25F6 is a generic OBD-II powertrain code in the speed, idle & cruise group.
- 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
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Common causes
- 01Failed AIR pump motor or impellerMost likely
- 02Check valve seized by exhaust sootPossible
- 03Corroded or cracked air injection pipePossible
Can I drive with P25F6?
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 P25F6
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P25F6. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Fix other faults first
If other codes are stored, start with power-supply, sensor-circuit and communication codes. They can cause this code as a side effect.
- 3
Check live data
Watch the related sensor and actuator readings in live data (Air pump B, Air check valve, Air pipes) and compare them with expected values in the service information for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Failed AIR pump motor or impeller; check valve seized by exhaust soot; corroded or cracked air injection pipe. 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.
P25F6 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
- Air pump B
- Air check valve
- Air pipes
P25F6 FAQ
What does P25F6 mean?
P25F6 means “AIR System B”. A general fault in the second secondary air injection (AIR) circuit. Detected by the O2 sensors which expect a lean swing during cold-start AIR pump operation but do not see one.
Is P25F6 serious? Can I keep driving?
We rate P25F6 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 P25F6?
The most common causes, from most to least likely: Failed AIR pump motor or impeller; Check valve seized by exhaust soot; Corroded or cracked air injection pipe. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P25F6?
Typical labor is about $190–$625 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 P25F6 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 P25F6 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.