P25F7

Code

Generic P — Powertrain

AIR System B Incorrect Flow Detected

Brand: Generic

Type: P — Powertrain

Views: UK: 26 EN: 37 RU: 20

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Blocked or collapsed air delivery hose on AIR system bank B
Stuck open or stuck closed AIR system check valve or one‑way valve
Failed secondary air pump for bank B (mechanical or electrical)
Faulty AIR solenoid/air switching valve or its actuator
Wiring fault: open, short, poor connector, or corroded pins in pump/solenoid circuit
Blown fuse or bad relay supplying the AIR pump/solenoid

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Failed emissions test or high tailpipe emissions
Possible rough cold idle or extended warm‑up time (if secondary air is required for cold emissions)
Hissing or whistling air leak sound from engine bay or underhood
Reduced fuel economy (rare)

What to check

Retrieve freeze frame and live data; confirm P25F7 as active or historic and note vehicle conditions when code set
Visually inspect AIR system plumbing on bank B: hoses, fittings, clamps, injection ports, check valves, and pump location for damage or disconnection
Check fuses and relays for the AIR pump/solenoid circuits
Command the AIR pump and solenoid with a scan tool to verify operation while monitoring voltage and current
Perform a smoke test of the intake/AIR plumbing to find leaks or collapsed hoses
Inspect and test the one‑way/check valve for proper operation (directional check)

Signal parameters

Commanded AIR pump state: ON/OFF or PCM duty cycle when active
Pump supply voltage: approx. battery voltage (~12 V) when commanded ON at connector
Pump current draw: should be steady and within manufacturer spec (sharp increase or zero current indicates problem)
Solenoid/air valve coil resistance: within spec (open or short indicates failure)
Presence of airflow at injection port when pump/solenoid commanded (physically verify by hand or with flow tester)
Pressure/flow sensor feedback if fitted: commanded vs actual flow/pressure differential across check valve

Diagnostic algorithm

Read and record codes and freeze frame data. Check for other related codes and clear codes if appropriate after repairs.
With key ON, verify fuses and relays for the AIR pump/valve circuits. Replace if faulty.
Visually inspect AIR plumbing on bank B for collapsed, disconnected, or blocked hoses and for damaged check valves. Replace or repair any damaged components.
Use a scan tool to command the AIR pump and air switching solenoid. Confirm pump runs and the solenoid actuates. Listen and feel for airflow at the injection port.
Measure voltage at the pump connector while commanded ON. If no voltage, trace wiring back to relay/fuse/PCM and repair open/shorts/poor grounds.
If pump receives voltage but does not run, test pump current draw or bench test pump. Replace pump if failed.
Remove and bench‑test check valve/one‑way valve. Replace if stuck or leaking. Reinstall with correct orientation.
Perform a smoke/leak test on the AIR plumbing to locate leaks or blockages. Repair as needed.
If airflow is present but PCM still reports incorrect flow, verify any flow/pressure sensors and inspect the exhaust (catalyst restriction). Update PCM software if a known calibration issue exists.
Clear codes, run readiness/drive cycle, and recheck. Monitor live data to verify flow matches commanded values and code does not return.

Likely causes

Clogged or collapsed hose between pump and injection port
Defective AIR pump (won’t run or low output)
Stuck or leaking one‑way check valve allowing backflow or no flow
Solenoid/valve not actuating due to bad coil, wiring, or relay
Blown fuse or weak battery/poor ground preventing pump operation

Fault status

⚠️ Status

AIR System B Incorrect Flow Detected — the secondary air injection system on bank B is not producing the expected airflow (either insufficient, excessive, or inconsistent), triggering an emissions‑related fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours