Hey everybody. I'm about to purchase my first truck (so happy), and I need to get some advice on what kind of mechanical inspection I should go through before handing over my $$$. Keeping my eye on a number of listings, but my first choice is a '06 Sierra with the 4.8L, auto trans, and 140k miles. I know to crawl over the entire thing looking for leaks and rust (I'm only searching in the South and West to avoid rust altogether), as well as jacking the wheels up to push on the wheel at 12 and 6, and 3 and 9 to look for play. Check cylinder compression for sure...but what else? Thanks.

 

Maintenance records if you can get them. Check to see if the oil is really dirty.

 

Get a decent OBDII code reader/live data scanner and plug it into the OBDII port and scan the system for codes. The better OBDII code readers will also read the control modules for the transmission, ABS, Body Control Module. Write down codes that are retrieved and well as any codes marked as pending or historical. Next google each Diagnostic Test Code (DTC) along with the year, make, model, engine size to see what the codes are referring to.

 

Hello; The 4.8 may be a good choice. I have one in my truck. Been good for over 20 years so far. A thing to consider is the AFM system (cylinder deactivation) built into V8 engines. I think such started in 2005. Regular hydraulic valve lifters are replaced with types which mechanically stop the valves from opening. A fuel saving gadget which has questionable advantage in terms of saving fuel. But when that system fails can take out an engine. If my information is correct the system should be on the 2006 V8.

A thing i try to do when looking at older vehicles is to get the seller to not have started the engine on the day I come to look it over. I have the owner start it up cold while i stand where i can see the exhaust. You also can hear things such as piston slap.

 

The 2006 4.8L does not have AFM. That's what I drive. AFM I think started in the 5.3L, in 2005, but was not rolled out in engines other than the 5.3L until starting in 2007.

 

Thanks for the info. This is the first I'm hearing that awful fuel management system made it into any engine before 2007. And the 5.3L is what I'm looking for. I wonder if there's any official source of information for this?

 

what year did gm start afm on v8 engines - Search

Hello; Here are links to GM AFM in vehicles. Earliest seems to be 2005. There was a time during the pandemic when a lack of chips caused GM to sell some V8's without AFM. I do not know exactly how to find out which trucks had that eliminated.

It would seem the 2006 you mentioned likely does have AFM.

I see ads for electronic devices which disable the AFM. A thing is the altered hydraulic valve lifters will still be inside the engine. It is those modified lifters which are the failure point. It is not clear to me that simply turning the function off electronically stops a failure of the lifters.

In the older GM small blocks you could get at the lifters by removing the intake manifold. Not so on an LS. pretty sure the heads have to come off.

good luck

 

• AFM Years: 2007-2018
• DFM Years: 2019-Present
• Most Problematic: 2007-2013, 2019-2020
• Most Reliable AFM: 2014-2018

The 5.3L V8 is GM’s most common engine with AFM/DFM technology. According to Summit Racing’s technical resources, all 5.3L engines from 2007-2018 featured AFM, while 2019 and newer models use the more complex DFM system.

Hello; I stand corrected. from one of the links is the above list. For the 5.3 it may not be on the 2006. The information is a bit confusing.