P0491 - Secondary Air Injection System Insufficient Flow Bank 1

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3    What is this?
Table of contents

P0491 Possible Causes

  • Intake leak
  • Damaged AIR system components
  • Faulty AIR Solenoid Valve
  • Faulty AIR system relay

How do I fix code P0491?

Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

Cost of diagnosing the P0491 code

Labor: 1.0

The cost of diagnosing the P0491 code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle's make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.

Possible Symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

P0491 Description

An air pump is used on the vehicle to lower tail pipe emissions on start-up. The Powertrain Control Module (PCM) grounds the Air pump relay control circuit which energizes the Air pump. The PCM also grounds the Air combination valve vacuum control solenoid circuit, which energizes the Air vacuum control solenoid. Vacuum is then applied to both Air combination valve diaphragms which opens the shut off valves. The PCM enables both circuits simultaneously when Air system operations id desired. When the AIR system is active, then Air pump forces fresh air into the exhaust stream in order to accelerate catalyst operation. The AIR combination valves replace the conventional check valves. When the AIR system is inactive the shut off valves prevent air flow in either direction.
OBDII Code P0491 - Secondary Air Injection System Insufficient Flow Bank 1 - AutoCodes.com

P0491 More Information

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Information for specific makes

  • P0491 AUDI Secondary Air Injection System Insufficient Flow Bank 1
  • P0491 BMW Mass Air Flow Sensor Low Flow Limit Detected Bank 1
  • P0491 FORD Secondary Air Injection System Insufficient Flow Bank 1   
  • P0491 MINI Mass Air Flow Sensor Low Flow Limit Detected Bank 1
  • P0491 VOLKSWAGEN Secondary Air Injection System Insufficient Flow Bank 1

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