Red Lightning Bolt/Engine light, no heat on gage

Brelksj

Brelksj

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Joined
Jan 8, 2022
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17
Location
VA
have a 2008 Rubicon Unlimited, 108,000 miles.

While driving last night, out of no where, the red lightning bolt and check engine light came on (code unknown). I also lost all indications of temperature, the needle dropped below the "C". I also seemed to lose some heat in the cabin. Also, when I got off of the highway and was stopped at the light, the fan was running and would not turn off. There was no indication of engine performance change.

Background: This weekend I changed out the radiator, both hoses, and the thermostat. It ran fine on Sunday, Monday, and the first part of Tuesday. Could this be the throttle body sensor? When I was changing the thermostat and I unhooked the sensor, one of the hold back clips on one of the sides broke. It still had the clip on the one side, so it seemed to hold the sensor in place.

Thoughts?
 
For the lightning bolt do a battery reset.

The temperature problem did you burp out all the air out of the system? Jack the front of the jeep up and have the radiator cap off and start the jeep and let it idle. Then top off the radiator.
 
Yes, I jacked it up and let it run and periodically topped it off.

I just drove to Autozone and used their code reader and got code P2181 (Cooling System Performance) and secondary DTC P0128 (Thermostat Rationality). While I was there I got another thermostat just in case. Sucks, cause I just replaced the thermostat.
Once I left there, the red lightning bolt did not come back on, but the engine light stayed on. The needle on the temp gage rose a little bit, then dropped, then rose. I got a little heat. When I got to the house and parked, the temp needle rose again and then started getting heat. I drove around the block and the needle dropped again. It never got above the 1/4 mark. Weird.
 
MOTORAD was what I ordered from Rockauto. I bought the Failsafe brand at Autozone. I guess I am going to switch the thermostat.
Still doent explain why the lightning bolt came on.
 
Brelksj said:
Yes, I jacked it up and let it run and periodically topped it off.

I just drove to Autozone and used their code reader and got code P2181 (Cooling System Performance) and secondary DTC P0128 (Thermostat Rationality). While I was there I got another thermostat just in case. Sucks, cause I just replaced the thermostat.
Once I left there, the red lightning bolt did not come back on, but the engine light stayed on. The needle on the temp gage rose a little bit, then dropped, then rose. I got a little heat. When I got to the house and parked, the temp needle rose again and then started getting heat. I drove around the block and the needle dropped again. It never got above the 1/4 mark. Weird.
Click to expand...
Sounds like there's still air in the system
 
UPDATE:
Checked the thermostat and it was stuck open. Brand new thermostat only lasted three days, uggg. Put another one in. Working fine now. Still don't explain the red lightning bolt coming on. Hasn't come back on for two days.
 
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Brelksj said:
UPDATE:
Checked the thermostat and it was stuck open. Brand new thermostat only lasted three days, uggg. Put another one in. Working fine now. Still don't explain the red lightning bolt coming on. Hasn't come back on for two days.
Click to expand...

Failing thermostat isn't uncommon, unfortunately. Not sure if aftermarket vs Mopar makes a difference, but I suspect it does. Least you got the heat figured out and hopefully all CEL's are done here forward. If that bolt returns, keep us in the know.

Cheers and stay warm.
 
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Currently dealing with this exact problem with my srt8. I have done some research and it seems to be common in 2008 jeeps or around that year. I have not found the issue but I assume it’s my thermostat but like you say it still doesn’t explain the lightning bolt. I’m curious did you ever figure that part out ???
 
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