Novak Conversions Jeep Wrangler JK shifters

Red lightning bolt / engine light, no heat on gauge

Brelksj

New Member
Joined
Jan 8, 2022
Messages
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.
 
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.
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.
 
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.

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.
 
  • Like
Reactions: BigAL07 and mrjp
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 ???
 
I have a 2017 Jeep Wrangler experiencing the same issue today. The lightning bolt warning light came on, and the temperature gauge and LCD screen are not showing any readings. I also noticed some coolant leaking from the radiator cap. I plan to replace the thermostat for the third time, as I’ve had to change it twice before due to it staying closed and preventing the engine from cooling properly. This time, I’ll be using the Mopar brand. I will also be following the recommended steps listed below.

Recommended Steps
  1. Replace the thermostat with Mopar as planned.
  2. Replace the radiator cap with a Mopar or high-quality equivalent (cheap caps can cause endless problems).
  3. Inspect or replace the coolant temperature sensor — if it’s not reporting correctly, you’ll still have gauge and ETC issues.
  4. Check the throttle body for carbon buildup and ensure the connectors are clean. A dirty or failing throttle body can trigger the lightning bolt light too.
  5. After repairs, bleed the cooling system thoroughly — air pockets can cause temp reading issues and overheating.
 
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.

I just had a motorad (motorad box with a murray thermostat inside) fail stuck shut after about a month. Switched to a mishimoto and problem solved.
 
Stuck open is a lot better than stuck closed.

That said, sticker shock on the t-stats.... the same t-stat I ordered a couple years ago is about $12 more. Imported by Gates, made in China. I didn't order that specific one, but I did pay over $40 for the housing/t-stat.
 
  • Wow
Reactions: JeepJeezy
Novak Conversions Jeep Wrangler JK shifters