Digital Temperature Readout

[Mike n Marina Wolfgram]

Looking for reasons as to why the digital temperature readout on my '04 Marquis 505hp fluctuates from 188 to 201.  Just started bouncing around within less than a minute or two.  Would this be a sensor Cat can easily diagnose???  Any ideas appreciated.
Mike Wolfgram

[Steve Huber]

Mike,
If your other readouts are stable., a bad sensor would top my list of suspects. An intermittent connection wouldn't appear to always give you the same range of readout and if the other digital ROs are OK, the monitor is good. I'm assuming the temperature ROs change when the engine is running at a constant speed and RPM.
Steve

[David T. Richelderfer]

Four things come to mind: 1) the temperature sensor has gone bad, as you called, 2) the thermostat is bad, 3) a connection has gone bad, or 4) the coolant level is low.

[Dave Atherton]

Good morning, I would look at two areas, first coolant level and on some Cat Engines
Builder added ( Coolant level sensor ) that is a little circuit board that in time connections
get dirty that will cause what is happing. Location if equipped is located off surge tank
On a 2 foot pigtail wire tucked into wire loom holding in place with zip ties. Dave has
Posted this before coolant level sensor. Second to the Wolfgram when Dave used Cat ET
On diagnostic engine readout/printout at Seven Feathers, looking at the ET printout you
should see under event codes the coolant sensor count. If the count is high will indicate
Bad connection at coolant sensor ( note: this is Caterpillar sensor not the coolant level
sensor aftermarket add on.) It if possible bad sensor but look at above first may find
Problem. Dave Atherton Retired Cat Mechanic