Technical Service Bulletins

Not a Cruise in the Park

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Not a Cruise in the Park

This bulletin applies to 2013-2018 Chevy Cruze vehicles. This bulletin is intended to produce direction and examples when diagnosing multiple DTCs, one of which includes U****Byte 71 DTC. Any control module may set this DTC for one of its inputs and data that is shared across the communication buss for other modules to do their respective functions.

The receiving module may set a 71 Byte type DTC. In these cases the DTC list should be examined for what control module or missing data the U codes point to and check for DTCs related to the managing modules’ inputs.

As a general rule, never replace components for “Invalid Data Received” codes with the component. Resolve the system-wide non-communication (not U codes) first and re-evaluate.

Following is one example in which an intermittent wheel speed sensor code was setting U codes across busses and the root cause was tracked back to the wheel speed sensor and EBCM messages.

Problem: The DLC shows “Service Stabilitrak” and “Service ABS.” When the EBCM sets any of the wheel sensor codes C0035-C0050, it yields “Service Transmission,” “Steering Assist Reduced” and “AWD off” in addition to “Service Stabilitrak” and “Service ABS” messages. This is in addition to several U codes corresponding to these messages which may include U0121, U0131, B1011, U0414, C0040, U0422, U0415, U2502, U0401, U0403 or U0402.

The EBCM would set the wheel speed sensor code intermittently, triggering a system malfunction message to be transmitted, resulting in multiple U codes across the chassis expansion and HS CAN busses.

The multiple U codes can cause misdiagnosis. An erratic wheel speed signal can cause this failure due to the miscommunication in the system when it intermittently fails. When you review the ABS data, you may find an erratic signal from the wheel speed sensor.  This can be caused by a faulty front hub wheel bearing.

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