Recently, I had installed an OEM Mopar dry block heater on my JKU. Unfortunately, it involved having the local shop repairing the threads that one of the AC compressor mounting bolts go into. They had to evacuate the system and remove the AC to perform the repair. I hadn't really driven it much since then until I left work today. It was still pretty cold in my area, so I had the block heater plugged in.
When I left work, the coolant temp gauge was working fine. But as I was driving home, I noticed a noise while I was at an intersection, which I later realized was the radiator fan. Everything seemed fine otherwise, no warning lights. Then on the last stretch home, about 4 miles into my commute, I noticed there was no reading on the temperature gauge and the radiator fan was still going. Panicked, I pulled over at the nearest side road and turned the Jeep off to check things out. I discovered that nothing appeared to be wrong. No coolant loss, no indication of overheating, but I did notice the lower radiator hose was cold as if the thermostat wasn't opened. Starting it back up, I carefully drove the rest of the way home.
After I got back in my garage, I scanned the Jeep and I got two codes:
P0116 Coolant Temp Sens Perf
U1402 Implausible Engine Temperature Signal Received
I also noticed that the lower radiator hose had started to warm up, so it must've finally opened. The AC clutch also appeared to be engaging more loudly, but there was no code for that, and it's possible that was just in my head (I tried engaging it and disengaging it multiple times to hear). The only thing I can think of is that some wiring got stretched, or bumped, or damaged during the service. I'm more concerned about the U1402 code, but it's possibly related to the first or the overall issue. Overall, I'm confused by the behavior of the thermostat, or the sheer coincidence of this happening all at once.
Interestingly, I found one other user on a different forum with virtually the same experience as me. His thread is here:
I reached out to him and found out that he never did get to the bottom of the issue. Evidently, he eventually crashed his JK and got a JL. Anyway, that's as far as I got and I'm completely at a loss. This is sort of a hail Mary, honestly.
There's even an instance of this on a 2010 with the 3.8:
www.jeepforum.com
When I left work, the coolant temp gauge was working fine. But as I was driving home, I noticed a noise while I was at an intersection, which I later realized was the radiator fan. Everything seemed fine otherwise, no warning lights. Then on the last stretch home, about 4 miles into my commute, I noticed there was no reading on the temperature gauge and the radiator fan was still going. Panicked, I pulled over at the nearest side road and turned the Jeep off to check things out. I discovered that nothing appeared to be wrong. No coolant loss, no indication of overheating, but I did notice the lower radiator hose was cold as if the thermostat wasn't opened. Starting it back up, I carefully drove the rest of the way home.
After I got back in my garage, I scanned the Jeep and I got two codes:
P0116 Coolant Temp Sens Perf
U1402 Implausible Engine Temperature Signal Received
I also noticed that the lower radiator hose had started to warm up, so it must've finally opened. The AC clutch also appeared to be engaging more loudly, but there was no code for that, and it's possible that was just in my head (I tried engaging it and disengaging it multiple times to hear). The only thing I can think of is that some wiring got stretched, or bumped, or damaged during the service. I'm more concerned about the U1402 code, but it's possibly related to the first or the overall issue. Overall, I'm confused by the behavior of the thermostat, or the sheer coincidence of this happening all at once.
Interestingly, I found one other user on a different forum with virtually the same experience as me. His thread is here:
P0116 with Block Heater use - JK-Forum.com - The top destination for Jeep JK and JL Wrangler news, rumors, and discussion
Stock JK Tech - P0116 with Block Heater use - I've got a somewhat strange problem. This is my first winter with the JK, and I've started using the block heater on days below freezing, usually plug it in 2-3 hours before I leave in the morning. This is a factory installed block heater according...
www.jk-forum.com
I reached out to him and found out that he never did get to the bottom of the issue. Evidently, he eventually crashed his JK and got a JL. Anyway, that's as far as I got and I'm completely at a loss. This is sort of a hail Mary, honestly.
Cooling fan and temp gauge mystery - JK-Forum.com - The top destination for Jeep JK and JL Wrangler news, rumors, and discussion
JK Electrical, Lighting & Sound Systems - Cooling fan and temp gauge mystery - On the way to work this morning, my rad fans turned on and didn't turn off again. Somewhere around the same time, my temp gauge showed a cold engine. By this time, I had been driving for 40 minutes. When I drove home...
www.jk-forum.com
There's even an instance of this on a 2010 with the 3.8:
Coolant temp readout error code
www.jeepforum.com
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