p0491 secondary air injection system insufficient flow bank 1
P0491 Secondary Air Injection System Insufficient Flow Bank 1
Definition: The OBD-II code P0491 indicates that the Engine Control Module (ECM) has detected insufficient airflow in the secondary air injection system for bank 1. This system is responsible for reducing emissions by injecting fresh air into the exhaust stream to help burn off excess hydrocarbons.
P0491 – Secondary Air Injection System Insufficient Flow Bank 1
Severity: Moderate
Common Causes
P0491 – Secondary Air Injection System Insufficient Flow Bank 1
Common causes:
- Faulty secondary air injection pump
- Blocked or restricted secondary air injection system
- Leaking or disconnected vacuum lines in the secondary air injection system
- Faulty one-way check valve in the secondary air injection system
- Electrical issues such as blown fuses or damaged wiring related to the secondary air injection system
Common Misdiagnosis
OBD2 Code: P0491
Description: Secondary Air Injection System Insufficient Flow Bank 1
Common Misdiagnosis: Replacing the air pump without checking for clogged or damaged hoses, faulty check valves, or electrical issues in the secondary air injection system.
Common Diagnostic Steps
OBD2 Code: P0491
Description: Secondary Air Injection System Insufficient Flow Bank 1
- Check for any stored codes and freeze frame data to understand the conditions under which the code was set.
- Inspect all related fuses, relays, and wiring for damage or corrosion.
- Examine the secondary air injection pump for proper operation and listen for unusual noises.
- Verify that the air injection check valves are not stuck closed or clogged with carbon deposits.
- Test the vacuum supply to ensure there are no leaks or blockages affecting valve operation.
- Use a scan tool to activate the secondary air system and monitor airflow readings from oxygen sensors.
- If necessary, replace faulty components such as pumps, valves, or hoses that are not functioning correctly.