mjm-1957

You need a new mechanic. Check fuse number 24 in the underhood fuse block.

I just looked yours up and it has it.

See if the exhaust is restricted. You can run it with the front O2 sensors out to check that.

Thats the beginning of the end for that unit. I am the transmission guy at a GMC Buick dealer and that code means the TCM is attempting to apply the convertor clutch and the rpm is not dropping enough meaning the clutch is slipping. The lining on the clutch comes off and the piston now has metal to metal contact with the convertor housing sending metal threwout the complete unit destroying the pump and lowering the line pressure burning up the clutches. Absolute horrible design and to make matters worse GM allows the TCC to slip all the time. What the hell were the engineers thinking when they

Make sure its not an exhaust leak before you start spending money or changing anything. Broken exhaust manifold bolts are very common and can sound exactly like a lifter or valve train noise,especially when the engine is cold.

Those trucks are known to have battery cables issues. Gm says to voltage drop the ground, positive and also the short positive jumper from the post to the battery fuse block. All should drop less than .5 volt while operating under a load. Have someone hold throttle to floor to turn off injectors and watch your meter while cranking. We change quite a few of them. Especially with that kind of mileage.

No recall, special policy N182202780-02, vacuum pump covered for 10 years or 150,000 miles.

Bad vacuum pump.

its called CMP ****** and it is in one of the engine data sections.

You will know if it has it when the pushrods bend and the lifter collapses.

We have had two other yukons doing the same thing and both turned out to be bad master cylinders. No external leaks just bypassing internally. I would replace it and go from there.

That is happening everywhere. We are doing at least one of those lifter jobs a week and sometimes 2-3. Absolutely horrible, also waiting on a 10 speed transmission that destroyed the forward planetary unit and sent chunks of metal threw out the whole transmission. That has 3105 miles on it and was ordered a week ago. Im sure the owner is so happy with his purchase.

Head gasket issue.

Your welcome. If you have never done that before I would recommend bringing it somewhere you trust and have them do it. The hub requires a special socket to remove the nut and then a puller to remove the hub from the axle. The inner seal must be replaced whenever the hub is removed and then the bearing preload has to be correctly adjusted when it goes back together. Also replace the axle flange gasket while you have the axle shaft out.

And a line bore.