2009 Chevy Silverado, AFM issues

Thomas Diagnostician Texas Posted   Latest  
2009 Chevrolet Silverado 1500 LTZ 5.3L (3 LC9) 4-spd (4L60-E) — 3GCEC23039G270725
P0300 Misfire
Afm Lifters


Have a 2009 chevy silverado with the afm lifter system. We have replaced the AFM lifters and lifter guides on both banks bank 1 and bank 2. Also we replaced the VLOM valley plate as well. Unfortunately at the time the gm strike was going on so we were unable to get the lifters from the dealer. We went aftermarket on the lifters. Originally the vehicle came in with a p0300. But we could see in history cylinder #1 had almost 400 counts of misfire. So we knew cylinder 1 was the issue. The valves would not open and stay shut indicating the afm lifters were not returning to the inactive mode. A compression test confirmed this we had low compression. Customer approved repairs and also they approved the other side as well to replace the afm lifters. We put it all back to together. Ran it for a test drive and all seemed well until we returned from the test drive and cylinder #1 would not kick out of the 4 cylinder mode into v8 mode. So again #1 cylinder valves are staying shut. 

So question if anyone had run into this heres what we know.

  1. We did oil pressure test and found it to be around 25 psi when hot. We did it at the oil filter housing. Now the oil sending unit was reading low but we found the sending unit filter was clogged up with debris. So once we replaced the sending unit and filter the reading went back to normal. Could this have clogged up the VLOM plate?
  2. when we do an active test on cylinder #1 to cut it out. It works in disabling the cylinder but it wont return to inactive mode it stays stuck in active mode. If you rev up the engine to about 3000 rpm it kicks back out on its own. I feel this is more of a flow control issue or pressure dropping not allowing the lifter to go back to v8 mode. 
  3. Right now we have taken the head back off on bank 1 and inspected all the afm lifters and camshaft lobes as well. Can't really seem to find any issues with these. Could we have a bad afm lifter since its aftermarket? We are really scratching our heads. Before we replace the lifters again we'd hate to do this job a 3rd time. Also I heard about the lifter bore and needing to measure it. Unfortunately we don't have a dail gauge to measure the bore of that size. If its over sized I could see where the pressure would bleed off. I put the lifter inside the bore and moved it up and down I know its not the best method but it didn't feel loose in the bore. 
  4. Lastly It seems as though oil pressure is getting to the afm lifter but for some reason its bleeding too much pressure or not getting enough pressure to make the pins inside the lifter return to locking mode. If the camshaft is bad from what we've heard how can you go about to test this? Without removing the camshaft? Since our issues remains the same with cylinder #1 could the cam bearings be bad allowing for the oil pressure to leak? How could we test this? We've done several of these and this has been our problem child so to speak.

We dont' have the testing equipment to pressurize the vlom lifter plate as it states in the manual so we go by compression testing and how the system works. Any thoughts on this, we'd really hate to just condemn the motor if its something fixable. 

Sorry for the long post. Thanks! 

Jerry Owner/Technician
South Dakota

Find a tuner in your area and have the AFM shut off. Go to lt1swap​.​com lots of good info there.

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Caleb Diagnostician

Aftermarket lifters do not work. They must be OE.

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Rob Owner/Technician
British Columbia

A friend of mine who has a shop just went through the same problem you have encountered, aftermarket lifters where the problem. I had warned him but cost was the factor, now it's really costing him.

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Harm Technician

Next time just do an Afm Delete and using a HP tuner interface unit and then its real easy to shut it off. just costs a license. I have done a fem of just even turning v4 mode off and customers are gettin 1-2 L per 100km better fuel mileage. Even at your point right now wouldnt hurt to try.

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Geoff Diagnostician

shoot I just saw something about oil pressure testing on these and I can't remember where it was. It said/showed there are two different ports you are supposed to check. One maybe is on the front of one head and one spot is in the back of the Vee. The pressure should be nearly the same. There are also the screw on adapters that go in place of the oil filter. Definitely get that set if you do…

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George Owner/Technician

Out here if the engine has internal issues they get a used one...unless it still runs....then they just leave it. Same here in the remote parts of Alaska. So many low mileage cars that drive around at 25 MPH all day long. Start it , drive it 3 miles and shut it down . They never really get hot enough here in Skagway unless they run it up the Mt for 2 hours to Whitehorse in the Yukon, Canada. I…

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Michael Diagnostician

On number 4, the lifter unlocks with oil pressure and locks with no pressure. Did you clean the filter at the engine oil pressure sensor? youtube​.​com/watch?v=mkly7X…

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Gail Technician
North Carolina

Reread his post. Paragraph #1 has your info. The oil pump pickup o-ring fails on these dropping the oil pressure. How many miles on this one?

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