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Alrighty, here we go...first time post...please be kind.

I've got a '08 JKU which I bought in Aug '15 with 40k miles. I live in Middle Georgia. I'm a 35+ year computer engineer and I wanted something to tool around with my son, to teach him auto mechanics...like my father did me.

That same month I got the Jeep, when it was around 98 degrees, I got the code P0481, which I changed out the fan and reset the code with no problems. Same thing happen last year in Aug '16 and a similar hot day. Replace the fan and reset the code. Problem went away.

About three weeks ago, when it was around 98 degrees AGAIN, I had to do the same thing; replaced the fan and reset the code. However, this time, the code keeps coming back. Now, I evidently get a P0481 every time I turn the air conditioner on. I've even got good reproducing the code.

  • Start with disconnecting the battery to reset the code.
  • Run the vehicle as long as you want. When the coolant temp gets around 205 degrees, the fan kicks in and cycles, as long as you DON'T engage the AC.
  • When you turn on the air, as soon as the fan kicks on, the P0481 code registers, check engine light lights, and the fan stops. At this point, without the fan running, the engine gets immediately hotter.
If I'm going down the highway, I can run the air, traveling at 55mph. As soon as I slow down, the check engine will light...

FYI, I'm using a Garmin ecoRoute ODB-II adaptor and my Garmin GPS to watch the temp. Everything's fine, no matter the speed, as long as I don't turn on the air conditioner. The temp stays around 195-205 degrees and the fan cycles. As soon as I engage the AC, P0481 and no more fan.

Anyway, here's the things I've done to no avail:

  • Flushed the coolant several times and refilled with 50/50 coolant.
  • Replaced the cooling fan
  • Replaced the hi-speed fan control relay (behind the driver-side headlamp)
  • Checked and rechecked the wiring from the hi-speed reply to the TIPM
  • Checked the low-speed fan control relay in the TIPM
  • Inspected the TIPM (TWICE)
  • Replaced the engine coolant temp sensor (TWICE)
  • Checked and rechecked the wiring from the ECT to the TIPM
I'm at a lost. Help!
 
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