News Technical Service Bulletins

Camaro Noise Emanates From Front End

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KEYWORDS Chevy Mitchell 1

In this example, the vehicle is traveling straight (steering column position shown in blue). The left rear wheel speed sensor (WSS) (green) is spiking, while the right rear WSS (red) is not.

Some owners of a 2010-2015 Chevy Camaro might comment about a brief and intermittent ratchet, grind or anti-brake system (ABS) pump motor noise heard from the vehicle front when traveling in a straight line at slow speeds, usually less than 20 mph.

This may be due to a spike or drop in the speed of any wheel speed sensor (WSS). This spike/drop in speed signals the electronic brake control module (EBCM) to prime for a stability or traction event. Typically, no codes will be stored for this concern. No indicators or messages will be displayed with this noise unless the StabiliTrak or traction control system goes active.

1. Connect GDS2, set to monitor EBCM>Antilock Braking Data, then duplicate the concern several times under the conditions described by the customer.

2. Turn off the StabiliTrak and attempt to duplicate the concern again. To turn StabiliTrak off, press and hold the StabiliTrak/TCS button until the Traction Control Off light and the StabiliTrak Off light illuminate on the display. If the concern does not occur when StabiliTrak is off, then press and release the StabiliTrak/TCS button to turn the system back on and continue with this diagnosis.

3. Review EBCM>Antilock Braking Data Session Logs in GDS2. Specifically monitoring the WSS parameters for one of the WSS inputs to either spike up or drop down in a speed inconsistent with the speed reading of the other 3 wheel speed sensors. Typically, a 3 mph or greater variance may be detected in one or more data session logs, which will indicate which WSS and hub bearing need further inspection. In rare cases, it could be as little as 1 mph variance between WSS. It is suggested to use the Line Graph to plot out the steering angle sensor (to know when the vehicle is going straight) and both rear WSS parameters first. To do so, select the parameters you wish to plot by clicking on the parameters in the Diagnostics Display Data Display tab, then click on the padlock to move that parameter to the top of the list. Once the parameters are selected, move to the Line Graph tab to view an overlaid plot of the selected parameters. The front WSS parameters can be viewed later if the cause is not found in the rear, but the cause is more common to be found with the rear parameters. You must zoom in to view the fine detail needed to isolate the cause, as this is only a slight difference spiking down or up from the other WSS.

Important: The WSS and the hub bearing are two separate components and are serviced separately. While swapping the WSS from side to side can be performed, it is not recommended as the WSS is not likely to be the cause unless physical damage is present on the WSS itself.

Inspect the WSS and the hub bearing for physical damage, contamination or debris. Clean as needed and re-evaluate. If damaged, replace.

Note: There is some confusion over where the encoder is located on the hub. It is a brown rubber ring. It is not located behind the ring, and this ring is not just a bearing seal. It is the encoder.

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