Some 1999-2009 Volvo models (complete application list below) may produce a vibration when driven at highway speeds. If a wheel balance doesn't remedy the condition, a likely cause, says Volvo, is an overly small wheel hub center cone diameter. The smaller-than-normal center cone results in the wheel/tire assembly being mounted to the hub with an offset, which causes the vibration trouble. The problem will be most obvious at the front of the car, although the issue can occur in the rear, as well.
Start your diagnosis by examining each wheel hub. If any hub looks bent or deformed, replace both the hub and its corresponding wheel. If the hubs look okay, use a digital caliper to measure the center cone diameter, as shown in the illustration above. The reading should be 2.559. On some hubs, however, you'll get a reading of about 2.500. Although that's only .009 out of spec, it's enough to cause a wheel to run with an offset and result in vibration issues. Replace a hub if its center cone diameter isn't 2.559. Warning: Don't assume the center cone diameter on a new hub will be within spec. Volvo reports that there are lots of hubs in its parts pipeline with out-of-spec center cones. Always check the diameter with your digital caliper before installing a new hub.
Once you've got a good hub installed on the car, check the center hole diameter of the corresponding wheel. It should be about 2.600. If the diameter is off by more than a thousandth or two, replace the wheel, as well.
Vehicles that are susceptible to the vibration troubles are 1999-2006 S80 models; 2001-07 V70, V70XC and XC70 models; and 2001-09 S60 models.
Toyota reports that the rear dome light on some 2001-02 Sequoia trucks may flicker or stay on continuously. According to the car maker, the problem typically occurs when the switch is set in the Door position, and is caused by a short in the dome light itself. Installing a redesigned dome light assembly, part no. 81240-0C030, should eliminate the condition.
GM reports that the Low Traction and/or ABS light may illuminate on some 2004-06 Pontiac GTOs, even though none of the wheels are slipping or losing traction. One likely cause, says the carmaker, is an insufficient air gap between a rear ABS wheel speed sensor and tone wheel. The condition can occur at one or both rear wheels.
Start your diagnosis by getting the car on a lift and removing both rear wheels. Now measure the air gaps between the rear wheel speed sensors and tone wheels. You should see a minimum clearance of .059 inch at both wheels. If you do, this information doesn't apply; continue troubleshooting until the problem is resolved. If either air gap is less than specified, remove the affected speed sensor, install a specially designed shim, part no. 90278359, under it to increase the clearance, then reinstall the sensor. To complete the fix, install the wheels, lower the car and go on a road test to confirm that the warning light(s) stay off.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected].