Hello Everyone I am hoping that someone here can help me with a problem which I am having with my 2002 Trailblazer LTZ, (4.2 litre l6). Vehicle has done 157000 miles.
It started a few months ago when the oil gage would drop to zero when hot and at idle and the low oil pressure warning came on followed by stop the engine.
The oil level was on the maximum and it had been recently changed, (5W 30 Mobile synthetic with a quality Hastings oil filter used regularly). I changed the oil pressure sender unit, (switch) and the VVT Solenoid, both were showing signs of leaking oil. The gage read OK for a while and then it started happening again. This time I removed the oil pan and front engine cover and fitted a new and improved oil pump, oil pick up tube and strainer and these were all genuine GM parts used. As a precaution I removed the instrument cluster and fitted a new oil pressure stepper motor and re-soldered all the joints around it. The problem still did not go away. I had hooked up a traditional master oil pressure gage and this gave me steady readings 75lb psi on a cold start up and after around 60 minutes under driving conditions, (45lb psi) it would drop down to 19lb psi at idle. The engine sounds very good, no noises and drives well. I then changed out the first oil pressure switch and made sure that the replacement was a genuine AC Delco switch and while doing this I "flicked" to starter to ensure that there was no blockage at the oil pressure sender switch port. The problem is still there. Therefore I am beginning to wonder whether the PCM needs to be either changed or reprogrammed? I cannot find any TSBs on this issue and I don't have a Tech2 scan tool. The problem is there as others have commented on it, however there are no fixes shown? I am looking forward to hearing from someone who may know. Thank you Harry