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2006 Cadillac Escalade
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31 Posts
Discussion Starter #1
About 2 weeks ago, on my 45 mile drive to work, i noticed my temperature gauge only reading about 185. After a few minutes, i noticed it drop even further. I’m constantly looking at my gauges and normally my truck runs just below the 210 line on the gauge. A few days later i was able to borrow a scanner from a friend and i was able to look at live data. On the highway, watching the scanner, it seemed that the temperature would actually dip down into the 160-170 range ( hence the P0128 ). Driving around town, it seems that the temperature does go up to the 200 range. Outside temperature has been between 50-75 degrees during this time. So today, i let the truck idle, because i wanted to see if the fan or fans were running constantly or erratically. The truck idled for 20-30 minutes and finally reached 225 degrees on the scanner ( the cluster gauge was slightly above the 210 mark ) and both fans kicked on at the same time. They both turned off when the temperature got down to about 200. I was under the impression that the slow speed fan comes on before the high speed fan and that the high speed fan was mostly in use when the A/C was on. I was originally thinking that this was just a thermostat that was stuck open but now I’m more confused than ever. I’m planning on flushing the cooling system, changing the thermostat and replacing the hoses. Just not sure what to do about the fans. Any help would be greatly appreciated
 

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2006 Escalade AWD w/DiabloSport tuner,Jet Performance throttle body/MAF,Airaid MIT
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P0128 code seems like a faulty thermostat issue; which is also causing the fans erratic behavior I assume. Hopefully a new thermostat will fix the issue.
 
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2006 Cadillac Escalade
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31 Posts
Discussion Starter #3
Does anyone know how the electric fans are supposed to work? At what temperature should each fan come on?
 

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P0128 CADILLAC Possible Causes 1.Leaking or stuck open thermostat 2.Low engine coolant level 3.Insufficient warm up time 4.Faulty engine coolant temperature sensor 5.Engine coolant temperature sensor harness is open or shorted 6.Engine coolant temperature sensor circuit poor electrical connection.

Hope this helps
 

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2006 Cadillac Escalade
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31 Posts
Discussion Starter #6
Its at the full line...I understand what the code is...I’m just trying to figure out if it’s the fan’s running constantly while on the highway or if its the thermostat
 

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To test your thermostat take it off the car and stick it in a pot of boiling water, if it opens partially it's bad if it doesn't open at all it's bad if it opens all the way it's good and something is wrong with your fan.
 

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I would worry about the thermostat first because it doesn't matter if your fan doesn't work if your thermostat is broken because if it's stuck shut the cooled fluid can move through the engine to cool it.
 
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