Erratic temp gauge on 99 5.0

[MINERALGSVT]

Recently, the temp gauge starting acting erratic- will peg into the red and the "check gage" will come on then go back to norm. The car is definitely not overheating.

Anyway, I will test the sending unit, but my question is this-

Today, when the gage pegged into the red, I did the 'system check' in the center console. Of course, it said 'temp ok' - does the 'system check' read directly from the ECM or does it come from the sending unit? What about the gauge?

Thanks!

 

[MINERALGSVT]

Just a follow up. I checked the sending unit and it was fine. I then figured it was time for a coolant flush anyway with winter coming, so I had the dealer flush it for $89.

Problem gone.

 

[bobflood]

Recently, the temp gauge starting acting erratic- will peg into the red and the "check gage" will come on then go back to norm. The car is definitely not overheating.

Anyway, I will test the sending unit, but my question is this-

Today, when the gage pegged into the red, I did the 'system check' in the center console. Of course, it said 'temp ok' - does the 'system check' read directly from the ECM or does it come from the sending unit? What about the gauge?

Thanks!

As info: According to the schematic, the message center gets it's engine temp info from the same sensor as the gauge. The ECM gets it's temp info from a separate sensor.