Multiple U-code Diagnostic Information – With one having symptom Byte 71 – 2013-2019 Buick Cadillac Chevrolet GMC

Bulletin No.: PIT5569A Published date: 07/16/2019
Preliminary Information
PIT5569A Multiple U-code Diagnostic Information – With one having symptom Byte 71
Models

Brand: Model: Model Years:

VIN:
from to

Engine: Transmissions:

All All 2013 – 2019 All All
All All

Involved Region or
Country North America
Condition
The following bulletin is intended to provide direction and examples when diagnosing multiple DTCs,
one of which includes U**** Byte 71 DTC. Any control module may set DTC for one of its inputs and
that data is shared across the communication buss for other modules to do their respective
functions. The receiving module may set a 71 byte type DTC.
Symptom Byte
-71
Symptom Byte Description

-Invalid Data
Symptom Byte Definition
-This sub type is used by the Electronic Control Unit to indicate a signal was received with the
corresponding validity bit equal to Invalid or post processing of the signal determines it is
invalid.
In these cases the DTC list should be examined for what control module or missing data the U codes
point to and check for DTC’s related to the managing control modules’ inputs.
As a general rule, never replace components for “Invalid Data Received” codes within the component.
Resolve the System-Wide non-Communication (not U codes) first and reevaluate.
Cause
Below 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.
Correction:
Problem # 1: The DIC shows Service Stabilitrack” and “Service ABS”

Condition: 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 the above messages
which may include U0121 U0131 B1011 U0414 C0040 U0422 U0415 U2502 U0401 U0403 U0402.
Cause: 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 buses. 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.
Correction: Diagnose the Wheel Speed Sensor using SI. In this example it was diagnosed that a
faulty front hub wheel bearing was the cause of the erratic wheel speed sensor signal.
Version History
Verson 2
Modified 05/17/2017 – Created on
07/16/2019 – Updated to add Model Year