8.1.1 Gauge Drivers
OEMs are increasingly selecting datalink-driven intelligent displays for their applications instead of traditional gauges and lamps directly driven from sensors or engine ECU.
If a needle type analogue gauge is required to display an engine parameter such as engine speed, oil pressure, or coolant temperature, it is recommended that the OEM use a gauge or display that can use the parameters
broadcast by the ECU on the J1939 datalink.
As an alternative, traditional single wire gauge “senders” may be used if a suitable tapping is available. If this implementation is required, please contact the electronic applications team to discuss requirements.
A traditional tacho signal may be obtained from the “W” terminal of the alternator, although this will not be as accurate as the value sent on the J1939 datalink.
Warning: The engine wiring harness must NEVER be modified to use the signal from the sensors connected to the engine ECU. This action would invalidate the engine warranty.
8.1.2 Lamp Outputs
The lamp strategy is designed to display the maximum amount of information on the minimum number of lamps.
There are six lamp outputs available:
Lamp Description Pin Allocation
Red Stop Lamp Pin 60
Amber Warning Lamp Pin 59
Wait-to-Start Lamp (Cold Start Aid) Pin 63
Low Oil Pressure Lamp Pin 62
PTO Mode Lamp Pin 61
Maintenance Due Lamp Pin 58
It is mandatory for the OEM to fit the Red Stop Lamp (1), Amber Warning Lamp (2) and the Wait-to-Start Lamp (3) unless a datalink-driven intelligent display is fitted, which fulfills the specification outlined in the next section.
Lamps four, five, and six are optional.
8.1.3 Indicator Lamps Logic
Warning Lamp Shutdown Lamp
Lamp State Description of What Lamp Engine State
(also known as Alert Lamp) (also known as Action Lamp) Status is Indicating
Bulb Check When the ignition is turned on Key on but engine the EMS will illuminate each has yet to be
bulb for 2 seconds and cranked.
On On extinguish them afterwards.
No Faults With both lamps off while Engine is running Present engine is running then there with no detected
are no currently active faults.
Off Off warnings diagnostics or events.
Active Should the warning lamp Engine is running Diagnostic illuminate during engine running normally but has this indicates that an Active one or more faults Diagnostic (electrical fault) with the engine
On Off is present. management system.
Derate Should the warning lamp illuminate Engine is running (Invoked by and the shutdown lamp flash but has one or
Active during engine running this indicates more active Diagnostic) that an Active Diagnostic (electrical diagnostic events
fault) is present. The diagnostic is that have initiated
On Flash sufficiently serious to invoke engine derate.
engine derate.
Warning Should the warning lamp flash Engine is running (Warning during engine running this normally but has only) indicates that one or more of the one or more
engine protection strategy warning monitored engine values have been exceeded parameters
Flash Off but not to a level that will outside of the
invoke derate or shutdown. acceptable range.
Derate Should both the warning lamp and Engine is running but (Warning shutdown lamp flash during engine one or more of the and Derate) running this indicates that one, or monitored engine more, of the engine protection strategy parameters has gone
values have been exceeded beyond beyond that of the level required to invoke engine warning only and has
Flash Flash derate. now exceeded those
set for engine derate.
Engine Should both the warning lamp and Engine is either Shutdown shutdown lamp illuminate during shut down or
engine running this indicates shutdown is imminent,
that either: one or more
1. One or more of the engine monitored engine protection strategy shutdown parameters have values has been exceeded. gone beyond that of
On On 2. A serious Active Diagnostic has warning or derate and
been detected. have now exceeded Shortly after (time duration those set for engine to be agreed) engine shutdown. Or a serious
will shutdown. Active Diagnostic has been detected.
Engine Management System Related.
8.1.4 Datalink-Driven Intelligent Displays
Displays may be connected to the engine ECU using J1939 datalink.
Some products that use the CDL may also be compatible. Please contact your local applications team to confirm before selecting a CDL display.
Devices that are connected to the J1939 datalink should meet the following standard if the OEM does not intend fitting the indicator lamps described above.
8.1.5 Minimum Functional Specification for J1939 Display
• The display is always on when the engine is running.
• The display should be line-of-sight of machine operator during machine operation.
• Display of the whole J1939 fault code including Suspect Parameter Number, Failure Mode Indicator, and Occurrence Number.
• Clear indication of what action, if any, the operator is required to take.
• Display of engine speed.
• Audible or bright lamp warning when new fault code is detected.
• The scaling of any gauges (e.g., coolant temperature) should be such that the needle is not far to the right of vertical when the engine is in normal operation (this would give the impression that the engine was
abnormally hot, when in fact it is running within its design limits).
Caterpillar will, under no circumstances, change the engine J1939 implementation in order to resolve compatibility issues with gauges or displays other than those supplied directly by Perkins.
Gauge manufacturers may contact the electronic applications team, however, for information and assistance in ensuring that their products are compatible with the engine ECU.
To support new standards and requirements, Caterpillar may add to the fault code table. Therefore, any active engine fault codes including those not recognized or referenced should be displayed. Caterpillar recommends that any suspect parameter number and the associated failure mode identifier are displayed.
8.1.6 Customer Triggered Engine Fault Codes
The engine will raise fault codes (event codes) when its design limits are exceeded; for example, for excessive coolant temperature. The fault code algorithms are carefully designed and validated so that they do not cause spurious codes when there is in fact no fault.
Some intelligent instrument clusters available on the market are also capable of raising fault codes themselves, based on the information that the engine transmits on J1939 such as “engine coolant temperature.” The machine designer could set a limit that is more conservative (lower) than the warning threshold defined by Caterpillar. This raises the possibility that the display will say that the engine has a fault when the engine is in fact running within its design limits. This is undesirable as it may result in a service technician being called to resolve a problem when in fact no problem exists. It will also cause damage to the reputation of Caterpillar and of the OEM.
Caterpillar recommends therefore, that intelligent displays DO NOT have their own fault detection for engine over temperature/oil pressure etc, but that they use the fault codes generated by the engine, sent in the J1939
“Diagnostic Message#1 (DM1).”