What are the symptoms of a bad air injection pump?
Key signs include a check-engine light with secondary-air system codes, a whining or grinding noise from under the hood, and little or no air being delivered into the exhaust during operation — especially on cold starts. These symptoms often indicate a failing secondary air injection pump, though other components of the system can cause similar warnings.
What the air injection pump does
The air injection pump is part of a vehicle’s emissions-control system. It pushes fresh air into the exhaust stream during cold starts and at idle to help burn off excess hydrocarbons and reduce emissions. The pump can be belt-driven or electric, depending on the make and model. When it fails, the emissions system may throw warnings and the vehicle may not pass a smog check.
Common symptoms
Below are the most common indicators that the air injection pump may be failing. These signs can also be caused by related components, so a professional diagnostic is recommended.
- Check engine light on with emissions-related codes for the secondary air system (such as P0410–P0413 in many vehicles) or other air-injection codes.
- Unusual noises from the engine bay, especially a whining, squealing, grinding, or rattling sound when the system is operating or at startup.
- Little or no air being delivered into the exhaust during the system’s activation, sometimes evidenced by a lack of airflow or a faint hiss instead of a healthy flow.
- Rough idle or intermittent misfires during cold starts when the secondary-air system should be active.
- Reduced performance or difficulty during startup, particularly in older vehicles where the AIR pump is used during cold starts.
- Failed emissions test or trouble passing a smog check due to inadequate emissions treatment.
- Drive belt showing wear, cracks, or tension issues, or visible leaks/loose hoses in the AIR system.
- Pump does not run at all due to a blown fuse, failed relay, or wiring issue.
These symptoms, taken together, suggest a potential malfunction in the air injection pump and warrant a professional diagnostic to confirm the root cause and prevent further emissions-related problems.
Diagnostic steps to confirm a faulty pump
To determine if the pump is at fault, a technician will typically perform these checks. The following steps help distinguish pump failure from other emissions-system issues.
- Scan for OBD-II trouble codes and verify that codes relate to the secondary air injection system.
- Inspect the drive belt (if the pump is belt-driven) for wear, cracks, or looseness.
- Check the air-injection pump itself for electrical power, ground, and proper operation when the system activates.
- Test the corresponding relay and fuse to ensure the pump is receiving power when commanded.
- Inspect hoses, check valves, and fittings for leaks or blockages that could mimic pump failure.
- Perform a flow or pressure test to confirm the pump is delivering the expected amount of air into the exhaust.
Correctly identifying the cause aids in choosing the right repair path, whether it’s a pump replacement, relay/fuse repair, belt replacement, or fixing compromised hoses.
Repair options and considerations
Repair options
Depending on the diagnosis, a technician may recommend one or more of the following: replace the air injection pump, replace the drive belt, replace the relay or fuse, repair or replace hoses and fittings, or address electrical wiring faults. In some cases, the entire exhaust or emissions system may require service if multiple components are degraded.
Maintenance and prevention tips
Regular inspection of the air-injection system during routine maintenance can catch wear or leaks early. If your vehicle is approaching a smog check, having the AIR system evaluated beforehand can prevent failed tests and last-minute repairs.
Summary
A bad air injection pump can manifest through a combination of a check-engine light with secondary-air codes, unusual noises, and reduced or absent air flow into the exhaust, especially during cold starts. If you notice these symptoms, have a qualified mechanic diagnose the secondary air system to confirm the pump’s condition and determine the proper repair to maintain emissions compliance and engine health.
