code 401

[glc4122]

about the coolant loss approx. erery two weeks, a small amount is needed because the low coolant light come on.

[BNaylor]

Unless you see visible external leaking it sure sounds like your intake gaskets. Do you have any sludge in the cooling system or coolant in the oil or crankcase? Look at the back of the oil filler cap for condensation or signs of coolant and in the radiator at the filler neck and radiator cap for sludge. And at the coolant reservoir?

[richtazz]

Do you know if the plastic upper plenum has ever been replaced? There is a known issue with the EGR stovepipe causing the UIM to warp and leak coolant. Since this is around the area that feeds the EGR gasses into the intake stream, it could also be causing your EGR flow codes.

[glc4122]

thanks for the reply everyone, there is no coolant in the oil, no yet. there is a small oil pocket laying on the front of engine approx mid way on the manifold, if this will help,but no oil in coolant.

[BNaylor]

Are you sure it is oil and not coolant? Coolant will look black or turn black after sitting there awhile and baking on the lower intake manifold.

[glc4122]

it sure looks like oil, any way to tell for sure by visual test?

[BNaylor]

The big question is if it is motor oil how did it get there? I am assuming you are referring to the stuff collecting at the lower intake manifold port runners and the area where the fuel injectors are located. In most cases it would be bad lower intake manifold port gaskets or even a bad UIM gasket so check those areas carefully. BTW - No oil flows through the UIM unless you have a bad PCV valve and it gets in via the PCV part of the UIM.

What condition are your valve cover gaskets in? Even if they are bad the oil will not go to that area but drip or settle at the area of the exhaust manifolds.

[glc4122]

i checked the o'rings on pcv housing and pcv valve. no o'ring on pcv valve. i purchased the kit at gm. it included pvc valve and spring and orange o' ring. should the pvc valve have a o'ring on it. maybe this is the problem?

[BNaylor]

As previously mentioned the PCV must have the black o-ring on it. See pic. This should take care of at least the P0401 EGR flow DTC. After corrective action just reset the DTCs and then after a few drive cycles see if at least the P0401 DTC clears.

[richtazz]

While you're in there replacing that o-ring on the pcv valve, look at the black plastic elbow that goes from the lower intake to the belt tensioner (located just below the PCV/Map housing). If it's wet around there, that may be the source of your coolant loss too. They can seep coolant, but not enough to end up on the ground.

[glc4122]

thanks again for the help about o'ring on pcv vale. will try and let you know results.

[glc4122]

yes, i put a new o'ring on pcv valve and the 171 & 401 code has stopped, but code 420 is still hanging around. when the check engine light comes on with this code, it will light up light and sometimes after shutting down engine and , the light will turn off. Is this common or should it stay on till reset? thanks for all the help everyone