I just purchased a 2009 Tahoe Hybrid. The truck was a GM Buyback Vehicle. On the disclosure statement, it listed low oil pressure light comes on intermittenly. Two days after delivery, the light came on a few seconds after starting it...(Remote Start). There was a very loud valve tap and the oil pressure gauge was under 20 psi. A message on the DIC " Shut engine Down" came on. I started it up 20 mins later, and the light was on again. After hitting the gas pedal slighty, the pressure came up and stayed up and the tap went away. I couldnt duplicate the problem again!!! Took it to the dealer and of course,,,,they could not find anything. Shouldnt it have thrown a code? Oh, I was parked on a slight incline.

Should I Be worried? I do have bumper to bumper warranty.

scott

 

due to an oil gallery casting problem. I believe they were 2008's and I have no total numbers. Mine has made some clattering on start up a couple of times but oil pressure was normal and now that its broken in (16k) I havent noticed it lately.

 

unlikely that a casting problem would go away. could be an issue with the VVT or cylinder deactivation which routes oil through different passages. Could be not switching completely and letting it flow somewhere. Could also have been something clogging the pickup [and would still be in the pan] or the pickup could be off and only producing pressure on a flat surface. did you try an incline again?

 

Thanks for the reply. I tried to reproduce it again by letting it sit on an incline overnight with negative results. I called onstar who said it did not through a code. I think the next time it happens, I will have it towed to the dealer.

 

How many miles on it?

Could be the usage of a non recommended weight oil. This trucks are on-off all the time, so I think if the oil weight is to heavy in a cold start could make some evidence. But if is not happening during normal driving could be that at op temp is good. So guessing u probably have a 10w30 or so when the recommended is 5w30....just an example, don't remember exact specs now.

Also on a gmt800 that I have, I cure the clattering sound with the use of M1 oil.

 

the Mobil 1 synthetic 5w/30 is recommended for the hybrid as it is a GM4718M oil. I am using the even better Mobil 1 extended performance 5w/30.

 

I am not sure if the oil pump is a geared or sleeved pump. It could also be a gerrotor pump Pressure and scavenge. I have noticed very minor transients in oil pressure based on vehical speed. Sounds like a vale sticking or the pump possibly by-passing, 20PSI hit the gas then normal at idle I would have GM look at it, does not take long to starf a bearing of oil momentarliy and then have a failure several miles down the road. just a thought.

 

Thanks for the reply. It happended again in the same driveway with the slight incline. Again , No codes were in the computer. However, OnStar did say a Bullentin was just issued # 2435251 on April 5th 2010 for Engine Code LFA which is mine. They told me it was something to do with the Spec Valve Oil Filter????? Its greek to me. I will take it to the dealer for the second time tomorrow.....As the world turns......I still love this Truck

 

Our engines have a variable flow oil pump that changes output based on need. Seems like there could be an issue with this system on your truck. I haven't looked at the system yet, so I don't understand how it works.

 

fjungman, interesting variable oil pump, can you fine out what type? Vane, piston, sleeve. Interesting.