2003 GMC Yukon 5.3 flex with the famous check engine light

Lightsout303

New member
Recently, the dreadful check engine light appeared during the awesome Colorado winter. Codes p0174,p0171, p0101, p0300. I just hit 87,000 and never had an issue. Only on cold mornings my Yukon will have a rough idle... I have the K/N cold air intake system, with a throttle body spacer. (This has been installed on my vehicle for almost 4 years) I also have a Super chip and Magnaflow exaughst. After reading the horror stories with the K/N oil that is used on the filter, I trashed that intake system. I replaced the spark plugs with the delco double platnums .040 gap. Also changed out the spark plug wires. Purchased a new cold air intake system, JET mass air flow sensor. I dont have any vacuum leaks, no loss of power, and my oil and coolant are at the correct levels. I checked the O2 sensors. My guess is the intake gaskets are bad??? I have been to many shops and have gotten too many different opinions which range from 1000 to 3000 dollars to repair on what "THEY THINK, "could be an issue. 2 potential problems... the oil neck seems loose, and the PCV hose is really easy to pull up? No funny smells from the exhaust.
Between Alldata and many forums, videos and advice I wont know which direction to go if replacing the gaskets fail. Any ideas??? I ordered (Fel-Pro Ms96587 Intake Manifold Gasket) Some people say replace the knock sensors at the time of the gaskets, is this true? I have had the codes cleared and they came back. I have cleaned the intake manifold and the throttle. If anyone has any ideas, I thank you in advance! The only 2 codes that keep coming back are p0171 p0174
 

Lightsout303

New member
update

Wanted to give an update...I replaced the intake gaskets and a knock sensor! My Yukon feels brand new again! This was my first time ever attempting work like this and it wasn't bad at all My philosophy is if you can troubleshoot a problem, you can fix it! I pulled notes from all data, read many forums and watched youtube videos of other people working on their vehicles. I dont claim to be a mechanic, I am a MECP advanced certified installer by trade. I saved myself atleast 6-1000 dollars, and it took me around 7 hours to complete.
 

Lightsout303

New member
update

Wanted to give an update...I replaced the intake gaskets and a knock sensor! My Yukon feels brand new again! This was my first time ever attempting work like this and it wasn't bad at all My philosophy is if you can troubleshoot a problem, you can fix it! I pulled notes from all data, read many forums and watched youtube videos of other people working on their vehicles. I dont claim to be a mechanic, I am a MECP advanced certified installer by trade. I saved myself atleast 6-1000 dollars, and it took me around 7 hours to complete.
 

johnnyidaho14

New member
Wanted to give an update...I replaced the intake gaskets and a knock sensor! My Yukon feels brand new again! This was my first time ever attempting work like this and it wasn't bad at all My philosophy is if you can troubleshoot a problem, you can fix it! I pulled notes from all data, read many forums and watched youtube videos of other people working on their vehicles. I dont claim to be a mechanic, I am a MECP advanced certified installer by trade. I saved myself atleast 6-1000 dollars, and it took me around 7 hours to complete.
Good day, I'm getting the knock sensor code for my 2002 yukon denali xl with the 6.0 engine and would appreciate any instructions or links i could get to for the detailed replacement of these two, thanks
 
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