Engineering Analysis EA09-004: Turn Signal Lamps

GM designed the MY 2004 and 2005 Chevrolet Malibu and Malibu Maxx vehicles with a daytime running lamp (DRL) system that uses the same filament (the high power filament of a dual filament bulb) as the front turn signals.

The high power filament operates at full battery voltage when functioning as a DRL.The DRL is illuminated whenever the headlamps are off, increasing the duty cycle of the front turn signal bulb.

The MY 2003 and earlier Malibu vehicles (Malibu Maxx was not manufactured for sale in the U.S. prior to MY 2004) used a headlamp based design, operated at a reduced voltage, for the DRL function; GM reverted back to this design on the MY 2006 and later Malibu and Malibu Maxx vehicles. Filament based bulbs have a finite life (hours of illumination) for any given operating voltage.

As a result, increasing the duty cycle of a bulb typically decreases the life span of the bulb.

GM identified and addressed two front turn signal/DRL and rear turn signal bulb quality issues early in MY 2004 production, however vehicle warranty claims for failed bulbs continued to occur.

To address the high warranty levels of bulb failures (90% of the warranty claims submitted to ODI by GM were bulb failures and 10% were socket failures), GM issued a technical service bulletin in March 2006 advising dealers to use a new specification of bulb when addressing service failures, and to also inspect the electrical sockets for thermal damage and replace if necessary.

In June 2006 (after subject vehicle production ended) GM changed the turn signal bulb specification to that of the TSB bulb in vehicle production also.

To date, ODI has not identified any allegations of crash, injury, or fire related to the alleged defect even though the subject vehicles have experienced 5 - 6 years of field exposure.

ODI's analysis of consumer complaints, both VOQ and manufacturer, shows a declining trend.

The warranty rate for turn signal bulb replacement is high however statistical analysis of the warranty data suggests that the majority of the original equipment bulbs have already been replaced.

GM conducted a safety recall (06V-263) for MY 2004-2005 Cadillac XLR to replace the front turn signal/DRL bulbs and the electrical sockets.

However GM advised that the turn signal/DRL bulbs/sockets on the subject vehicles differ from those on the recalled XLRs in several respects, including using bulb sockets with four electrical terminals as opposed to three, which improves the electrical connection, allows the bulb to operate at a lower temperature, and adds stability to the bulb in the socket; operating at a lower voltage, which increases vehicle bulb life; using vented headlamps, which allows bulbs to run cooler than those installed in a non-vented XLR headlamp; and using a clear bulb, which runs cooler than the amber bulbs installed on the XLR.Additionally, the warranty claim level related to subject vehicle sockets is unremarkable compared to other defect investigations into defective socket assemblies.

A safety-related defect trend has not been identified at this time.

Further use of agency resources does not appear to be warranted.

Accordingly, this investigation is closed.

The closing of this investigation does not constitute a finding by NHTSA that a safety-related defect does not exist.

The agency will take further action if warranted by the circumstances.

See attached report for further information.