Emission controls · Powertrain · generic (SAE-defined)
P0492: Secondary Air Injection System Insufficient Flow (Bank 2)
P0492 means the secondary air injection system is delivering too little air to the Bank 2 exhaust, the side of the engine opposite cylinder 1, during cold-start operation.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0492 sets
During the cold-start secondary air test, the powertrain control module (PCM) expects the Bank 2 upstream oxygen sensor to show a lean swing, or a pressure sensor to confirm flow. If the Bank 2 response is too small, the PCM sets P0492. The specific test is manufacturer-specific.
Common causes of P0492
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Weak secondary air pump
- Bank 2 check or combination valve stuck closed
- Carbon buildup in Bank 2 air passages
- Cracked or loose Bank 2 air hoses
- Slow Bank 2 upstream oxygen sensor
P0492 symptoms
- Check engine light on
- Possible abnormal pump noise at cold start
- No drivability symptoms in most cases
How P0492 is diagnosed
- Check whether P0491 is also present; both together suggest the pump or a shared component
- Confirm pump operation, relay, and fuse
- Inspect Bank 2 hoses and check valve
- Command the system and watch the Bank 2 upstream oxygen sensor
- Inspect Bank 2 passages for carbon blockage
Typical fixes for P0492
- Replace the Bank 2 check or combination valve
- Clean carbon from Bank 2 air passages
- Replace the air pump if both banks show low flow
- Repair hoses or connections
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
Commonly reported on V8 engines from several European makes and some Toyota trucks. Definitions can vary by manufacturer; check factory service information.
Related codes & warning lights
P0492 FAQ
What does code P0492 mean?
P0492 means the secondary air injection system is delivering too little air to the Bank 2 exhaust, the side of the engine opposite cylinder 1, during cold-start operation. The standard definition is "Secondary Air Injection System Insufficient Flow (Bank 2)."
Can I drive with a P0492 code?
Yes, generally. Expect normal drivability, but an emissions inspection failure until the problem is repaired.
What does it mean if I have both P0491 and P0492?
Low flow on both banks usually points to a shared part, such as a weak pump, a blocked pump inlet, or a failed relay.
Does P0492 apply to four-cylinder engines?
No. Bank 2 exists only on engines with two cylinder banks, such as V6 and V8 engines.
Keep researching
More emission controls codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.