Diagnostic Information to Clarify Effect of Secondary Air Injection System on Headlamp Flicker

This bulletin is a supplement to Corporate Service Bulletin 05-08-42-001 to clarify the effect of the Secondary Air Injection (AIR) system.

A customer concern regarding headlamp flicker, headlamps dim slightly and/or battery voltage fluctuates may be easily mis-diagnosed. It is very important to capture as much information from the customer as possible. Please refer to Corporate Service Bulletin 05-08-42-001 for additional information. This bulletin specifically addresses the operating characteristics of the AIR system. Refer to the Secondary Air Injection System Description section of SI for further information on the AIR system.

The Powertrain Control Module (PCM) will command the AIR system ON during Closed Loop operation to perform an active test. The active test will pass or fail based on the response from the HO2S 1. The active test consists of three tests run at 3-second intervals that are run during closed throttle (and other specific parameters, see SI for details) and will continue to cycle until the correct conditions are met and passed. The AIR pump motor has a steady current draw of 35-40 amps under normal operation, with a higher initial in-rush current. This current draw will reduce the available current for other components, such as headlamps, and accordingly may cause an intermittent dimming of the headlights. This can be compared to turning on a vacuum cleaner at your home with the corresponding dimming of your house lights. The condition can be duplicated using the special functions on the Tech 2® to command the AIR pump on and off.

To minimize the potential for customers who experience this condition, advise the customer to allow the vehicle to idle for 30 seconds after starting. This should allow the passive test to run and eliminate the need for the active test that may dim the lights.