Posted on a general Chevy truck forum but nobody has answered. Hoping somebody here can help since their seems to be alot of GM smart people in this forum, and this could be a universal type problem. 1999 Suburban 5.7 engine. Temp gauge has run low for a long time, just above 155 mark. Overheated recently due to stuck thermostat, so I'd like to get the temp gauge reading correctly, because who knows how hot it really got! Grounded temp sender plug to test and gauge tops out, which "they" say means the gauge is good/temp sender bad. Replaced temp sender and gauge is still wrong. I wouldn't mind if it just happened to be out of sync and always read low consistently. But sometimes it jumps to 210 as soon as truck is started, then drops back to 155ish after its warmed up. So what should I look at next? Saw some posts online about the teflon tape on the new sending unit messing with resistance, but can't see how that would make the old unit start reading bad. Any help or suggestions would be much appreciated! Please!

 

When I burned up my transmission due to towing in over-drive I decided I wanted to install a transmission fluid temperature sensor to help monitor the fluid temp in the rebuilt transmission. I then found that the information is available if you have the proper OBDII reader.

What I ended up doing is getting an Ultragauge. https://www.ultra-gauge.com/ultragauge/ The one I have stays plugged into the OBD port and I mounted it on the transmission tunnel hump. If you get one, note that they have two types. Only one has the transmission temperature feature.

Since the smallest number of readouts I could have on it was four, I decided to also display the transmission fluid temperature, the coolant temperature, actual speed (I have oversized tires) and the voltage. (The picture below is when I was curious about the MAP pressure.) I never liked the placement of the tick-marks on the coolant temperature gauge and as I suspected my voltmeter in the gauge cluster was off. So getting this Ultraguage has been a great solution for me.