Cars with traction control will have a switch to turn that system off. The ABS will likely set a fault code when it sees the wheels running at vastly different speeds, but the system does not activate unless the brakes are being applied. On every car I have seen so far, the ABS warning light will turn off after you turn the ignition switch off, then restart the engine. The fault code will remain in memory. That should be erased for two reasons. First, if a totally different problem develops in the future, the already-existing code could be confusing. Second, whenever a problem is detected, there is always a long list of conditions that must be met for a fault code to set. One of those conditions is that certain other codes can't already be set. For example, if a wire is cut to one of the wheel speed sensors, that will be detected as soon as you turn on the ignition switch. A fault code will be set and the yellow warning light will be turned on. At that point the ABS Computer will know it cannot rely on the sensor or for it to provide a signal, so it will suspend some of its self-tests, and it will not set a code for a missing signal. If you leave the code in the computer for the missing rear wheel speed signals, it may not test for proper signals from the front wheels, and that could result in an actual problem with just one front speed sensor going undetected.
This has a secondary concern, (sorry, I cannot think of a better word), where an actual problem goes unrepaired. Typically I read, "until I can get the money". The first problem causes some tests to be aborted so a second problem that occurs months later is not detected and no fault code related to it is set. It is not until the first problem is repaired, then during the test-drive, the other tests resume, and that is when the second problem is first detected. Your mechanic had no way of knowing there was a second problem when he calculated the repair estimate, and now he has to tell you more diagnosis time and repair cost are needed. We hate having to do that, and it is frustrating for car owners too. You incorrectly assume the car was not diagnosed correctly, or it was not repaired correctly. This is even more common on GM front-wheel-drive cars where failure of front ABS wheel speed signals, due to normal wheel bearing wear, occurs in as little as 15,000 miles. If one failure is repaired right away, the second, different failure will be detected two to four months later, and it will be obvious the cause is different. When you wait for many months with the first failure is when you get unpleasantly surprised to find the second failure no one knew about.
With your car, it is a simple procedure with a scanner to erase any fault codes that set by running the car on a hoist. Then, if a real problem develops later, it will be detected right away and you will know about it.
I greatly prefer listening next to each wheel bearing with a stethoscope to find the noisy one, but there is another way to consider. Jack one wheel off the ground, place the transmission in neutral, reach over the top of one front tire and wrap your fingertips around part of the coil spring. With your other hand, rotate the wheel and tire. If that wheel bearing is noisy, you will feel the vibration in the coil spring.
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Saturday, December 3rd, 2016 AT 6:26 PM
