The problem: my wife's Jeep is a 2010 JKU with the 3.8 and automatic transmission. We bought her back in 2018. She has 144k miles on her. A while back when out running errands the CEL and Traction light came on. Barely got her started to hobble home. Once home I plugged in the reader and the following codes came up: C121C, C2100, P0340 and P0344. We went down the rabbit hole that is the internet and the easiest and most likely fix seemed to be the sensor. Given age and mileage it seemed reasonable. Swapped it out and things were fine for a few days then the dash light popped again, same codes. This time when I checked I noticed water/liquid in the female end of the sensor. It's not rocket science to know that's not right and there was no indication of where it came from or what it was. Blew out the sensor and plug with a compressor to dry it and put it back together. Once again, she ran fine for a few days, even had a 300-mile round trip road trip without incident. I did check it before heading home on that trip and there was some moisture, so I dried it out again. A few days after getting home, dash lights again. We hit a point that I wasn't sure what to do. Took to our Jeep shop and they said it was a bad sensor and put a new one in. We had discussion around the moisture, and they said it could be weeping in along the wire harness. It "failed" again on a short trip out of town. This time they replaced the plug on the wiring harness. We drove it around a few days, literally just 50 miles around town and it's doing the same thing. This time when I dried the sensor I used a Q-Tip to soak up the moisture and noticed it was the same shade as the engine coolant. How would engine coolant be getting into the sensor when there is no sign of leaks anywhere? The Jeep shop had said if it happened again, they'd have to find a wire harness and replace the whole engine harness (mucho money as you can imagine) and right now I don't believe that will resolve the situation. Once I dry the sensor and the connection she runs fine for a bit, then she doesn't so it seems obvious the moisture build up is the problem. After this morning work I'm convinced it's engine coolant but I have no idea how it's getting into the sensor.



Has anyone seen this situation and have some suggestions? The attached images are from the day of this post, so very recent. I appreciate any assistance and if you need more info I'll try to respond ASAP.

 

Quote: How would engine coolant be getting into the sensor when there is no sign of leaks anywhere?

I'll state the obvious: If it's coolant, it's getting into the connector because it's leaking from the cooling system.
You need to look more closely.
Intake gasket is nearby. Thermostat and its housing with heater hose are nearby.
If you can't see a leak with a closer look, I would put some dye in the coolant and look with a black light.

 

I agree that something is leaking but it must be very subtle. Today I made sure everything around it was dry & I let it sit & run to heat it up, heard the cooling fan cut in & out a couple of times. No sign of a drip from the thermostat or anywhere around it. As it sat & cooled I checked back periodically to see if anything dripped due to the expansion/contraction of heating & cooling. Nothing that I could see of any even tiny leak. I may have to try that process a few times & of course check it daily.

 

This is certainly not a "fix", but a good shot of dielectric grease in that connector should keep the moisture from causing havoc while you are hunting down the real issue.

 

I've thought about that. Get a good amount of the Dielectric grease into the connector and IF the coolant is making its way in around the wire end of the connector, just maybe it would stop future intrusion and if it doesn't throw a code after several days, then I'll have a better idea if where it's getting in. Then I'll just have to find the source.

 

[QUOTE=ronjenx;4414981]Quote: How would engine coolant be getting into the sensor when there is no sign of leaks anywhere?

I'll state the obvious: If it's coolant, it's getting into the connector because it's leaking from the cooling system.
You need to look more closely.
Intake gasket is nearby. Thermostat and its housing with heater hose are nearby.
If you can't see a leak with a closer look, I would put some dye in the coolant and look with a black light.[/QUOTE

Did you ever get this sorted out. Having the same issue with coolant in my Camshaft Position Sensor and there aren't any external coolant leaks.

 

[QUOTE=markelee66;4414980]The problem: my wife's Jeep is a 2010 JKU with the 3.8 and automatic transmission. We bought her back in 2018. She has 144k miles on her. A while back when out running errands the CEL and Traction light came on. Barely got her started to hobble home. Once home I plugged in the reader and the following codes came up: C121C, C2100, P0340 and P0344. We went down the rabbit hole that is the internet and the easiest and most likely fix seemed to be the sensor. Given age and mileage it seemed reasonable. Swapped it out and things were fine for a few days then the dash light popped again, same codes. This time when I checked I noticed water/liquid in the female end of the sensor. It's not rocket science to know that's not right and there was no indication of where it came from or what it was. Blew out the sensor and plug with a compressor to dry it and put it back together. Once again, she ran fine for a few days, even had a 300-mile round trip road trip without incident. I did check it before heading home on that trip and there was some moisture, so I dried it out again. A few days after getting home, dash lights again. We hit a point that I wasn't sure what to do. Took to our Jeep shop and they said it was a bad sensor and put a new one in. We had discussion around the moisture, and they said it could be weeping in along the wire harness. It "failed" again on a short trip out of town. This time they replaced the plug on the wiring harness. We drove it around a few days, literally just 50 miles around town and it's doing the same thing. This time when I dried the sensor I used a Q-Tip to soak up the moisture and noticed it was the same shade as the engine coolant. How would engine coolant be getting into the sensor when there is no sign of leaks anywhere? The Jeep shop had said if it happened again, they'd have to find a wire harness and replace the whole engine harness (mucho money as you can imagine) and right now I don't believe that will resolve the situation. Once I dry the sensor and the connection she runs fine for a bit, then she doesn't so it seems obvious the moisture build up is the problem. After this morning work I'm convinced it's engine coolant but I have no idea how it's getting into the sensor.



Has anyone seen this situation and have some suggestions? The attached images are from the day of this post, so very recent. I appreciate any assistance and if you need more info I'll try to respond ASAP.
did you get this sorted out. Having the same issue and no visible sign of an external coolant leak 

 

Having the same issue. Did you correct the problem? Did you find how the liquid was getting into the sensor housing?

 

Yes I did. It was a two-part fix. As you can see in the photo there is a small leak at the top of the water pump. We assume that when driving there was enough pressure at the higher RPM's it was spraying coolant up around the connection. In any case it wasn't visibly evident around the connection when the Jeep was sitting in the driveway. We guess the coolant spray was evaporating off the engine block due to the engine heat but remained in the electrical connection. Once the pump and gasket were changed that issue cleared. However, the malfunction wasn't resolved. Thinking there could be an issue with the wire harness, we replaced the harness that runs from the block on the firewall to the injectors, the sensor and a couple of other connections. That didn't fix it. The sensors that had been put in were all after-market. As much as it pained me, I spent the extra money on an OEM sensor (yes, I spent as much on the after-markets by the time 3 had been used, so we're chalking it up to life lessons) and once we put the OEM sensor in, we've been fine. She's running just fine, no codes or issues. For whatever reason, the Jeep didn't like the after-market sensor and needed the OEM. We made the decision to spend the money on an OEM sensor after talking more with a couple of people who have owned several versions of Jeeps, TJ's, CJ's JK's, and they said Jeep's can be finicky about sensors and use an OEM.

It's a lengthy response but we're hoping it'll help knowing what bases we covered and it will help you resolve your issue.

 

Markelee66,
Thanks for the update. It's bound to help others.