4l80e questions

[Coonburger]

My wife's suburban has a 4l80e in it shifts great no burned fluid but after while it'll pop a high transmission temp code and go into limp mode. Previous history on it was it was originally popping a shift solenoid B stuck open code so i replaced that now this one pops up. I dropped the transmission pan and i don't see a temperature sensor in there how does it pop a high fluid temp if there is no sensor in there. I drove it around got it to pop again and i took a thermometer to the bottom of the pan just to get a general idea the temp it was running it read 170. I am going to pick up a infrared thermometer here in a bit click that sucker every wheres. It has a transmission cooler and everything. Wouldn't if the transmission was getting that hot id feel slippage creating the heat or burned fluid?

[xaza]

Your infrared thermometer will help a lot for this. You will want to slowly run it across the entire trans cooler coil and watch for cool spots that can indicate low fluid flow. Also trying spraying the coil with water to clean it out. If you can get behind it and spray in the opposite direction of air flow it is better. Also check other coils in front or behind because they can restrict the airflow for that one.

[Warrlord]

The trans temp sensor is located in the internal wire harness, click me (http://www.rostratransmission.com/manuals/Form4157C.pdf)

Just to let you know, the most common issue (doesn't mean this is happening with yours) with this trans setting a high temp code is because the temp is getting too hot because of one or both of the trans coolers restricting flow thru it/them due to the torque converter clutch lining deteriorating. Those little flakes will go directly into the cooler(s). It doesn't always work but sometimes it does if you reverse flow flush the coolers with a can for each cooler of THIS (http://compare.ebay.com/like/260873390366?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar). The bad part is, if that's the case, the torque converter clutch will eventually fail & it'll set a P0894 code. Usually it's not the temp sensor that's faulty, it's something causing the temp to get too high.

[Coonburger]

mine is the older style harness that doesnt have it in the harness its self. Also it does not have the temp sensor located near the valve body like that diagram shows. i used the infrared on the pan and it read 172 degrees then cooler read 150 degrees. I searched all along the transmission the hotest spot i could find was right here it hooks to the motor which was 200 degrees.

[Coonburger]

i got looking at the plug for the exterior harness and the wires looking pretty shody so would crappy wires cause it to put out false codes?

[xaza]

As long as the wire is properly conducting no codes would be thrown; however a loose connection or broken wire definitely would.

[Coonburger]

got looking at the wires closer and L and M wires both have bare wire showing right at the base by the plug. so maybe its throwing off what temp it thinks its reading, could that be a possibility?

[Coonburger]

replaced the harness still does it, checked the ohms that the sensor is reading and according to the chart its reading 150, but still popping a overdrive ratio error and a high transmission temp error.

[Robert B]

.........give up and sell me the T case behind ur tranny :D .....i dont know man i dont like auto trannies cause they never seem to work for me well