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Group 38 Instrumentation, VNL, VNM
Diagnostics Mode
The Diagnostics mode provides two functions:
•
Diagnostic Messages - Reports the status of vari-
ous vehicle sub-systems.
•
Cluster Self Test Mode - Contains several tests to
check the cluster.
Diagnostic Messages
Fig. 18: Diagnostic message path
The vehicle contains one or more Electronic Control
Units (ECU's). Each ECU monitors or controls a particu-
lar vehicle sub-system. For example, an Engine ECU
monitors engine conditions, an Anti–lock Brake System
ECU monitors ABS conditions, and so on.
The ECU's are connected to each other and to the clus-
ter by a pair of wires known as the SAE J1708/1587
data link. The ECU's communicate with each other by
sending and receiving messages in a format specified by
SAE J1587.
Note: SAE J1587 is an industry standard which defines
the format of electronic signals and information transmit-
ted between truck and bus electronic components.
SAE J1708 defines the hardware and basic protocol
(data formatting) requirements for the truck and bus
electronic communications system.
The cluster can display active and inactive fault codes in
the Graphic Display. The message path from the J1587
data link to the Graphic Display is shown in the figure.
Each diagnostic message consists of a:
•
Message Identifier (MID) code
•
Sub-system Identifier (SID) or Proprietary Sub-
system Identifier (PSID) or Parameter Identifier (PID)
or Proprietary Parameter Identifier (PPID) code
•
Fault Mode Indicator (FMI) code
An FMI describes the type of failure detected in the sub-
system identified by the PID/PPID or SID/PSID. MID,
20
PID, SID and FMI codes are standardized and are listed
in the SAE J1708/1587 Specification. PPID and PSID
are unique for Volvo and are listed in the following sec-
tion. The following section also includes a list of MID,
PID/SID and FMI codes which may be displayed as text
messages.
The figure on Fig. 19: Example of a diagnostic message
in the Graphic Display, page 21 is an example of a mes-
sage indicating that a problem with the engine boost
pressure has been detected. In this example, the fault
still exists, and has occurred 3 times.
To see Diagnostic Messages:
1
Turn on the ignition. The engine may be started. Di-
agnostic messages from all J1708/1587–supported
vehicle systems are accessible.
2
Use the Mode button to display DIAGNOSTICS
MENU.
3
Use the Up and Down buttons to display DIAGNOS-
TIC MESSAGES.
4
When DIAGNOSTIC MESSAGES is displayed,
T3009132
press the Set button. RECEIVING DATA, PLEASE
WAIT will be displayed while the systems on the
J1587 data link are polled.
5
When the first message appears, the Set button can
be pressed to toggle the display between the text
description and the received data. If the display
shows "UNKNOWN" in any line, press the Set but-
ton to display the MID, PID/SID and FMI.
a. If the condition that caused the currently dis-
played fault still exists, the cluster will display
"ACTIVE."
b. If the condition that caused the currently dis-
played fault has gone away, the cluster will
display "INACTIVE."
c. The number of times a fault has occurred will
be displayed when available. In some cases, a
short message may also be displayed.
6
Record all codes displayed.
7
To display the next stored fault, press the Down but-
ton.
If the Graphic Display detects a complete failure of the
J1587 data link between the instrument cluster and the
other system modules, it will display DATA LINK BRO-
KEN. In this case, the actual wires used for the J1587
data link should be inspected for damage.
If the Graphic Display does not receive a response from
any of the individual modules on the J1587 data link, it
will display the name and number (MID) of the system
and NOT RESPONDING.
Design and Function
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Troubleshooting
