|
|
|
|
|
|
The eBearing News
September 2, 2005
GM Recalls 800,000 Trucks
Over Corroded Hub Bearing Sensors
copyright © 2005 eBearing Inc.
General Motors Corporation (USA) announced it has changed its strategy and consented
to voluntarily recall over 800,000 of its most popular and profitable light trucks.
This U.S. market recall involves the same vehicles and defect as a recall program
GM has already been conducting in Canada for almost a year, beginning in late 2004.
It also mirrors an already active
investigation by the U.S. National Highway Traffic Safety Administration (PE05-020);
launched in May, the NHTSA investigation covers more than 1.3 million GM light trucks.
article: Hub Bearing Sensor Failure Investigation Hits 1.3 Million GM Trucks
Included in this latest 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.
However, while the NHTSA investigation includes vehicles in 20 states, GM's recall includes 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.
In late 2004, GM recalled 150,000 of the same light trucks and SUVs in eastern Canadian
provinces (Ontario, Quebec, Newfoundland, New Brunswick, Nova Scotia, Prince Edward Island) to
address the complaint.
Both recalls were prompted by corrosion-related problems with the front wheel bearing
hub assembly speed sensor. Corrosion fouls the
sensor and trigger, resulting in false wheel speed readings which in turn
cause the anti-lock braking system to malfunction.
 |
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.
|
GM said the corrosion issue is limited to areas where salt is used on the roads in winter months.
The salt brine can attack the sensor via its mount, causing rapid corrosion buildup. Because the
sensor must be precisely located for it to operate properly, corrosion can easily disrupt the signal.
In this situation, 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, when ABS
is activated 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.
At the time the NHTSA investigation was 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.
Now, however, GM is acknowledging thousands of U.S. complaints, including reports of 228 crashes
and 10 injuries.
Since our 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,
http://www.nhtsa.gov.
When the NHTSA investigation was 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 corrosion is a well-documented issue and has been affecting hub bearing-mounted ABS sensors for
over a decade in every corner of the world.
Another said, "If my boss told me to make a case to NHTSA that we only have corrosion-related
sensor issues on salted roads north of the Mason-Dixon line, I wouldn't do it. We're talking about
a confused ABS computer here, and the potential for crashes with real people getting
hurt. My neighbors and family drive these trucks, you know. No, I wouldn't do it."
All of our industry contacts agreed GM's initial position that U.S. failures were low was
just to, "buy time," since a recall 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.
In making the recall announcement, GM stated that its current U.S. inventory of wheel speed
sensors is 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."
As in the Canadian recall, customers will have the front bearing hub units serviced by cleaning
the units, then removing the sensors, cleaning and testing the sensors, and if necessary, replacing
the sensors. The sensor and forging area will be treated with Zinc-X to inhibit corrosion.
The NHTSA recall campaign is
05V379000.
|
|
|
printer-friendly version
|
|
- by Bruce A. Carr
from individual research,
tips and commercial sources.
Unauthorized reproduction is prohibited.
|
|
eBearing.com ... for everything that moves™
Entire contents Copyright 1999-2008, eBearing Inc. All rights reserved.
eBearing.com and "... for everything that moves" are registered
trademarks of eBearing Inc.
|
|
|
|
|
| |
eBearing.com ... for everything that moves™
Entire contents Copyright © 1999-2008, eBearing Inc. All rights reserved.
eBearing.com and "... for everything that moves" are registered trademarks of eBearing Inc.
|
|
|
