Lighting - Headlamps Flicker or Dim While Driving
Information IB05-04-S003Diagnostic Information On Headlamps Flicker or Momentarily Dim While Driving
Affected Vehicles:
2003-2005 Isuzu Ascender with 4.2L engine (VIN S).
Service Information
A concern regarding head lamps flicker or become dim while driving may be easily mis-diagnosed. It is very important to capture as much information from the customer as possible. Below is a guideline to assist with diagnostics.
Verify the customer's specific concern.
^ Does this occur when it is light or dark outside?
^ Under what type of driving conditions does this occur? (For example the vehicle speed, engine speed, throttle position, and etc.)
^ What was the outside ambient temperature when the condition occurred?
^ What accessories was the driver using when this condition occurred? (For example A/C, heated seats, rear defogger, etc.)
^ If the concern is at dusk, could it be the automatic headlamps changing from DRL to Headlamp mode and possibly back to DRL again?
^ Are there any other relevant operating conditions?
For Diagnostic Information refer to the following:
^ Isuzu Service Bulletin -IB04-04-S003, Info - Low Voltage Display on IP Gauge, Lights Dim at Stop Lights, Battery Discharged, No Start, Slow Cranking, Dim Lights at Idle, Low Generator Output
^ Service Information - Exterior Lighting Systems Description and Operation in the Service Manual
^ Service Information - Battery Inspection/Test (Non-HP2) in the Service Manual
^ Service Information - Charging System Test in the Service Manual
^ Service Information - Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories in Wiring Systems in the Service Manual
Important:
^ Keep in mind high current draw items may cause a noticeable dimming of lights and a fluctuation in the voltmeter may be noted and is a normal operating characteristic of the vehicle.
^ For 2004-2005 Isuzu Ascender with the LL8 4.2L engine only, the Secondary Air Injection (AIR) pump activation is thought to be the main contributor to this high current draw condition and is a normal operating characteristic of the vehicle. Refer to Secondary Air Injection System Description in the Service Manual for further information.
For customers whose driving habits tend to run the AIR pump diagnostic test that leads to concerns with the headlight flickering, if the vehicle is allowed to idle for 20 seconds prior to driving, this should allow the passive test to pass and prevent from running the active test that may dim the lights. The passive test should/will usually pass 99 percent of the time, and by allowing the 20 second idle period, it should almost eliminate the active test. Be sure to check for codes and correct related concerns if this condition repeats.
Additional high current draw items are rear window defogger, HVAC blower motor, along with other components.
For easier diagnostics, it may be possible to control or monitor these components with a scan tool.
It is important to inspect all related connections, grounds and battery terminals for integrity. A loose or corroded connection may exaggerate the concern, and may cause other symptoms. Refer to Testing for Intermittent Conditions and Poor Connections.
Corrections/repairs should only be made for specific concerns identified and not related to characteristic of high current draw components.
Attempts to repair this condition WITHOUT pinpointing a specific concern may lead to a repeat repair and a dissatisfied customer.
Isuzu encourages dealers to share this information with concerned customers.
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