Hello, Im new to the forum. I have a 2007 yukon and I got a "low oil pressur STOP ENGINE" come up. Took it to the dealer and they replaced the oil sending unit. That didnt take care of the problem, they now tell me they have to take off the manifold to check for restrictions. They do that and there were no restrictions ( at this point they tell me my bill so far was around $700. they then tell me they called GM and they said it could be the flow valve another $291 and if thats not it I still have to pay for all their guess work. This seem right?

if you call their normal outrageous rates right then yes, but it shouldnt have been guessing there is a tsb out for that.

PIP4158C: Low Oil Pressure Due To Seized Oil Pressure Relief Valve - (Dec 29, 2009)


Subject: Low Oil Pump Pressure due to Seized Oil Pressure Relief Valve

Models: 2008-2009 Buick Lacrosse, Allure (Canada Only)
2007-2010 Cadillac CTS-V, Escalade
2007-2010 Chevrolet Avalanche, Corvette, Silverado, Suburban, Tahoe
2007-2008 Chevrolet Monte Carlo SS
2007-2009 Chevrolet Impala SS, Trail Blazer
2009-2010 Chevrolet Colorado
2010 Chevrolet Camaro
2007-2010 GMC Envoy, Sierra, Yukon
2009-2010 GMC Canyon
2008-2010 Hummer H2
2008-2010 H3 Alpha
2008 Pontiac Grand Prix GXP
2008-2010 Pontiac G8 GT <~~~LOL @ the typo!
2007-2009 Saab 97x
with the Following Aluminum V8 Engine RPOs:
L76, L77, L92, L94, L99, L9H, LC9, LH6, LH8, LH9, LS2, LS3, LS4, LS7, LS9, LSA, LZ1

The following diagnosis might be helpful if the vehicle exhibits the symptom(*) described in this PI.
Condition/Concern:

Some customers may complain of low oil pressure, no oil pressure, and/or engine noise, which may be the result of a sticking oil pump pressure relief valve. In some instances, this may occur intermittently if the valve frees up when the engine cools down.
Recommendation/Instructions:

If SI diagnosis isolates low mechanical oil pressure at the oil filter housing and oil pressure sensor, replace the oil pump, flush the oil cooler lines (if equipped), clean the inside of the oil pan, change the oil and filter, and re-evaluate the concern.

Notice: If an engine noise is noticed after replacing the oil pump, follow the SI diagnosis and repair the engine as necessary.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for infor

A sticking oil pressure relief valve is generally the first thing you look at when oil pressure is low. Justin (as usual) has you on the right track.