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The eBearing News
January 24, 2006

GM Extends Hub Bearing Sensor
Recall to 1.3 Million Trucks
copyright © 2005 eBearing Inc.

General Motors Corporation (USA) announced it has agreed to stop fighting and conduct a key hard-fought recall, now encompassing more than 1.35 million of its most popular and profitable light trucks in the U.S. market.

The problem being addressed involves corrosion of the front wheel bearing speed sensor. Corrosion build-up inhibits the sensor's operation, improperly triggering a malfunction in the anti-lock braking system.

Yukon Denali
Launched in May 2005, the U.S. National Highway Traffic Safety Administration (PE05-020) investigation initially covered 1.35 million GM light trucks.

article: Hub Bearing Sensor Failure Investigation Hits 1.3 Million GM Trucks

GM originally sought to fight back all efforts to prove a problem existed. The company then agreed to conduct a limited recall in Canada, deflecting calls for a parallel recall in the United States.

Although later forced to conduct a U.S. recall involving 801,000 vehicles, GM successfully stalled off recalling the remaining 553,000 vehicles involved in the defect investigation.

Now, GM has been forced to capitulate across the board, recalling all 1.35 million affected vehicles in Canada and the United States.

Included in the recall are 1999 through 2002 model year GM light trucks and SUVs -- Chevrolet Avalanche, Silverado, Suburban and Tahoe; GMC Sierra, Yukon, and Yukon XL. A dealer contacted by eBearing said it may also include the Cadillac Escalade.

The wheel bearing hub assembly sensor corrosion problem causes false wheel speed readings. Because the sensor readings are still present, the ABS malfunction light is not illuminated, and no error is recorded by the vehicle's diagnostic computer.
ABS tone ring and sensor
ABS tone ring and sensor. The toothed ring
is mounted on the bearing spindle, while
the Hall-effect sensor mounts through a hole in
the stationary hub forging.

When the sensor sends an erroneous wheel speed signal to the ABS computer, it is interpreted as a need for the computer to continue activating the ABS to prevent wheel lockup. However, if ABS is still triggering at very low speeds, it prevents the wheels from coming to a complete stop because it continually releases and applies the brakes (at very low speeds, the computer normally ignores ABS signals in order to allow the wheels to come to a complete stop). In the affected trucks, the rear brakes then become the primary stopping power, which significantly lengthens stopping distances.

The corrosion problem officially came to light in late 2004, when GM recalled 150,000 vehicles in eastern Canadian provinces (Ontario, Quebec, Newfoundland, New Brunswick, Nova Scotia, Prince Edward Island) to address the complaint.

While the May 2005 NHTSA investigation included vehicles in 20 states, GM initially agreed to recall only vehicles in 14 northern states it termed "rust belt states" -- Connecticut, Illinois, Indiana, Maine, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Vermont, and West Virginia.

That initial 801,000 truck recall was launched in late August 2005.

article: GM recalls 800,000 trucks over corroded speed sensors

GM stuck by its 14-state claim until recently, when it was forced to concede the corrosion problem also affects another 553,000 trucks across an additional six states -- Delaware, Iowa, Maryland, Minnesota, Missouri, Wisconsin, and the District of Columbia.

When the NHTSA investigation was first announced, GM said it would not be recalling trucks in the U.S. because the high failure rate was solely in Canada. GM said at the time, "We are still gathering information in our response to NHTSA, but when we looked at this issue last fall, there was a significant difference in how often this issue occurred in Canada and in the U.S. We saw three incidents of this per 100,000 trucks in the U.S., versus 30 incidents per 100,000 in Canada. The numbers just haven't borne out the need for a recall."

By GM's math, it was admitting to receiving 39 complaints in the U.S. Yet NHTSA's investigation, launched at the same time, was based on more than 120 complaints, including 22 crashes and 4 injuries.

GM has since acknowledged thousands of U.S. complaints, including more than 228 crashes and 10 injuries.

Since our first article was published in late May, eBearing alone received dozens of calls and emails about the problem, from all parts of North America. All were referred to the NHTSA website,

When the NHTSA investigation launched, eBearing took the opportunity to speak to a number of highly regarded wheel bearing and hub unit designers and engineers, all of whom expressed disbelief that GM's problem could possibly be limited to Canada, or even northern U.S. states. Several pointed out that this corrosion problem is well-documented by the service industry and has been affecting wheel bearing speed sensors for over a decade in every corner of the world.

All of our industry contacts have continued to agree GM's position that U.S. failures are low has been to, "buy time," since such widespread recalls in the U.S. might overwhelm dealer service departments. Another said he knew GM's stocks of wheel speed sensors were depleted by higher-than-expected U.S. demand and the need to stock the Canadian dealerships with replacement sensors.

"Getting adequate supplies of replacement sensors out in the field is absolutely critical," one OEM engineer pointed out. "Remember, when a service writer hits any braking system problem, we can't let the truck go home with the customer even if the parts are on backorder; our liability will be infinite. Without enough sensors, those trucks will stack up on the lot real quick. And in a safety or recall service situation, we're obligated to supply loaners. Nobody has that many loaners. It would be a nightmare. Heck, it's going to be a nightmare, anyway."

In fact, GM has since confirmed that comment made to us back in May 2005.

Making the September 2005 recall announcement, GM admitted its U.S. inventory of wheel speed sensors was insufficient to meet demand for the recall. In its letter to dealers, GM said, "GM is working with its suppliers to obtain the required parts as quickly as possible. Based on the anticipated schedule, we plan to begin notifying customers in November 2005."

Notifications for the group of 553,000 recalls is set to begin in February 2006.

Customers will have the front bearing hub units serviced by cleaning the units, then removing the sensors, cleaning and testing, and if necessary, replacing the sensors. The sensor and forging area will be treated with Zinc-X to inhibit corrosion.

All NHTSA recall campaign documentation is here: 05V379000.

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- by Bruce A. Carr
from individual research,
tips and commercial sources.
Bruce Carr edited this content.
Copyrighted material; unauthorized reproduction prohibited.

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