PIC6073D

Bulletin No.: PIC6073D
Published date: 02/27/2018
Preliminary Information
PIC6073D Diagnostic Tip: EL-51578 MOST Bus Diagnostic Tool Kit
Models
Brand:
All
Model:
All
VIN:
Model Years:
2013 - 2018
from
All
Engine:
to
All
All
Transmissions:
All
Condition / Concern
Vehicles equipped with RPO IO3, IO4, IO5, IO6, RAO, or UY4 only.
The MOST Bus Diagnostic Tool Kit (EL-51578) has been released to help diagnose any of the following MOST bus concerns and/or
Radio DTC U0028 sym00:
Blank radio display
Steering Wheel Controls inoperative
DIC audio information page blank
Audio inoperative with normal chime operation
Radio Controls inoperative
The diagnostic information below may be helpful if any of these concerns are encountered.
Recommendations / Instructions
If any of the concerns above are encountered, review MOST BUSS Description and Operation and U0028 diagnostic procedures.
Always perform "Diagnostic System Check" prior to diagnosing a Radio U0028 sym00. If a MOST buss module has a circuit or terminal
fault, (power, ground, GMLAN/ECL wake up) then this would be the probable cause of the Radio U0028 sym00.
The EL-51578 MOST Bus Diagnostic Tool Kit has been released to aid in diagnosing MOST buss concerns. The kit contains header
connectors that are installed to bypass MOST bus modules. The bypass connectors also contain a terminal for verifying ECL voltages
(MOST control circuit). The kit does not contain a bypass for the radio, which is the master of the buss.
The Radio U0028 sym00 will be used to determine MOST buss state of health. If the module with the concern is bypassed, the Radio
U0028 sym00 will report as history. Infotainment functions will return with the exception to what the bypassed module controls. For
example, if the amplifier is bypassed and DTC U0028 sym00 changes from current to history, ignore the symptom of no audio as the
amplifier is bypassed. Other examples, display will be inoperative with HMI bypassed. DIC and steering wheel controls will be
inoperative with IPC bypassed. CD/DVD will be inoperative with Media disc player bypassed.
Usually there may be 1 of 2 modules suspect with a current Radio U0028 sym00 set depending on which Node positions are listed. If
both of these 2 suspect modules are bypassed and the Radio U0028 sym00 stays current, check the MOST bus circuits and ECL for
opens, shorts, high resistance, or terminal concerns.
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