Hi. I started my 2000 silverado 4.8 sc yesterday and this is what happened. I got code p0118 ECT sensor circuit high and p0122 TPS sensor circuit low. I cleared both codes and they did not come back and all was running fine . Could a low fluctuating idle at start up cause these codes . My idle has to be worked on in the tune at startup but i have had this idle for a couple years now and this has never codded anything. I noticed that at key off my ECT gauge crawls back up tp about half and my oil pressure gauge crawls also to about quarter but as soon as i move the key to ignition on they both zero out as normal as the engine is not warm at all and when i start the truck the oil press gauge is normal and goes up a bit if i gas it and the ECT rises to normal then when i shut off the truck with the key out both gauges crawl back up and they should be at zero . I noticed when i plugged back in my scan tool to see if i had any codes my ECT gauge would zero out but not the oil press, this is when the truck had cooled down for a few hours. Could both gauges be causing this or one because they could be on the same circuit as i still have to pull out the schematics. I am sure someone has seen this before me . This all happened yesterday as i never had this before and sense the last time i used my truck nothing has been touched .I could go down to my truck in the garage and gauges will be showing half ECT and Quarter oil press no key on and i even tried removing the battery and the same reading . Thank you. Eric.