What happens when the secondary air pump goes bad?

When the secondary air pump goes bad, fresh air will no longer be pumped into the exhaust system on startup. This will cause more unburnt fuel to be expelled from the tailpipe, which will most likely cause the vehicle to fail emissions testing. It may also illuminate a check engine light, and catalytic converter damage can occur over time.

Can you drive with a bad secondary air system?

Normally, the vehicle will still run and drive with a bad secondary air injection system. However, the check engine light might come on, and there may be a loss of engine power. On certain models, the electronic control module (engine computer) will place the vehicle in "limp mode" and only allow partial throttle operation if the secondary air system is not working properly.

What causes a secondary air injection system malfunction?

If the secondary air injection system fails, the usual culprit is a bad air pump. Moisture can damage the pump, as can dirt and debris if the filter is not working properly. Occasionally, the system will fail due to an air leak caused by deteriorated hoses.