2004 Denali Transmission & Other Issues

[SheniqueTheDenali]

First of all, I'm a new member so sorta take it easy on me lol. I have a 2004 yukon denali with about 300,000 miles on it. I got it at 250,000 miles and up until now, I have not had an issue like the one I'm experiencing. I'm thinking this may be an electrical or sensor issue, but I am unsure. About two weeks ago, the transmission started showing signs of surging when trying to hold speed at around 45mph. It would start to surge and I could accelerate slightly and it would smooth out. Fast forward to a few days ago, I drove about 15 miles with no issue. Got to my destination, put it in park and when I put it back in drive to pull off... nothing. No forward gears in 1,2,3 or D. No reverse. I pushed it about 10 feet, cut it off and waited about 5 minutes. Started it back up, put it in drive and made it about 100 yards before it quit pulling. I repeated this about 4 times with the same issue every time. I had it towed home where it sat for a day. Went out and started it, now I have a very rough idle with a P0102 check engine code. For the time I have owned the truck, I have never had the check engine light come on, or any rough performance from the engine. Putting it in gear, while holding the brake, the misfire gets worse. I have odd sounds coming from under the truck. It seems to go into all gears now, but I am weary of pulling out of my driveway. Checked transmission fluid, and it is full. No other issues that I am aware of. I do not know which transmission I have, only that it is a 2004 Yukon Denali AWD. Any information on where I should start would be greatly appreciated.

 

[nonickatall]

That sounds like several different problems.

If I understand you correctly, you mean that the automatic shifts up and down at a fixed speed?

This can be a problem with the throttle position sensor if the automatic does not know the accelerator pedal position.

Your error p0102, on the other hand, indicates a problem with the air mass sensor, which would also explain the poor idling of the engine.

However, as far as the noise and the lack of propulsion of the automatic are concerned, that sounds like too little oil, or a failure of the transmission.

Have you checked the oil, at warm transmission, with the engine idling, on a horizontal surface?

 

[SheniqueTheDenali]

It started off with lurching at the top end of 3rd gear about two weeks ago. Now it will not go into gear at all and the misfire started. I checked the fluid with the truck running and in neutral after it's warmed up and the fluid is full. It does not look or smell burnt. There is an odd noise from underneath now when I start it up, but it goes away after a couple seconds. I was just wondering if it could be an electrical issue somewhere as the misfire and the transmission not functioning happened at the same time. As I said, I have never had a missfire before and it's just odd that problem has started with the transmission not engaging. Just wondering if I should try to track down an electrical problem. Thanks for your reply!

 

[rockola1971]

P102 Is mass air flow is sending a low voltage to the PCM. The voltage is proportional to the air coming into the intake system. So you either have a bad Mass Airflow Sensor, Clogged up Intake Filter or a Squirrel taking a nap in your airbox....Could also be a Walmart bag sucked up into your airbox blocking airflow.
More than likely your tranny is fine and its the Mass Airflow Sensor causing all the chaos.

 

[Mozess523]

I do not know which transmission I have, only that it is a 2004 Yukon Denali AWD. Any information on where I should start would be greatly appreciated.

Sorry to hear. I believe it is a 4L60-E? Sounds like it’s due for a rebuild. How is the transfer case? Is there a lot of play in the transfer case? Is the transmission problem causing a misfire? May want to check the mass air flow sensor and clean out the air intake, replace the air filter. Sometimes I have been able to lightly clean the MAF, but you need to be very careful not to over do it and ruin the sensor. Might be easier to get anew MAF. It this sounds like there is a misfire due to the MAF and has a bad transmission. This is just an arm chair quarter back guess. But I would start with figuring out the transmission issues first then tackle the PO102 / misfire.

 

[rockola1971]

Sorry to hear. I believe it is a 4L60-E? Sounds like it’s due for a rebuild. How is the transfer case? Is there a lot of play in the transfer case? Is the transmission problem causing a misfire? May want to check the mass air flow sensor and clean out the air intake, replace the air filter. Sometimes I have been able to lightly clean the MAF, but you need to be very careful not to over do it and ruin the sensor. Might be easier to get anew MAF. It this sounds like there is a misfire due to the MAF and has a bad transmission. This is just an arm chair quarter back guess. But I would start with figuring out the transmission issues first then tackle the PO102 / misfire.

If the engine aint running right, the transmission wont operate correctly since ALL shift and Pressure control parameters of the tranny are a reflection and actuated accordingly by the PCM in reaction to the engine speed and load.

 

[SheniqueTheDenali]

Thanks a lot for all of your quick replies! I guess I'll just start by cleaning/replacing the MAF and work my way down to replacing the TPS, then draining the transmission, dropping the pan and changing out the filter as all of these are within my skill set. Anything further will probably be passed on down to my dad haha. If I find out what the issue is, I'll post it here. If anyone else has any further suggestions other than replacing or rebuilding the transmission, please hit me with them!

 

[MassHoe04]

Only replace what is discovered and confirmed to be not working. Don't just go throwing new parts all over the place unless you know it is not doing what it is supposed to be doing. A lot of times a good original GM part that has been working perfectly for 20 years can still be better than a brand new GM replacement part, because not everything is made the way it was originally.

There is a fortune to be made in replacement parts. It wouldn't be good business practice to make replacement parts that are going to last forever. If you need a replacement part now, they'll sell you one that will last a few years but not forever. That way, they have another chance to sell another replacement for that part and keep the money coming in.

If it ain't broke, don't replace it. Even if you intend to use genuine GM parts.

That is just my suggestion to keep in the back of the mind as things come up.
I tend to hang on to old, but still functional, parts I removed for a while. Just in case a new part turns out to be a dud, I can throw the old one back in until I can figure out what is going on or use it while I wait for another replacement to come in.
My issues tend to happen on Sundays, after parts stores have already closed.

 

[rockola1971]

Thanks a lot for all of your quick replies! I guess I'll just start by cleaning/replacing the MAF and work my way down to replacing the TPS, then draining the transmission, dropping the pan and changing out the filter as all of these are within my skill set. Anything further will probably be passed on down to my dad haha. If I find out what the issue is, I'll post it here. If anyone else has any further suggestions other than replacing or rebuilding the transmission, please hit me with them!

A quick n dirty check on the mass air flow sensor is tap the body of the MAF with the handle of a hefty screwdriver. Dont baby it but dont try to knock a hole in it either. Do this test with engine idling. The engine should stumble and then start idling correctly if MAF is good when tapped with the screwdriver. If the engine dies immediately then MAF is bad.

 

[SheniqueTheDenali]

So I broke the MAF lol. Costly mistake, but probably needs it anyway. Question though, how do I know if my 4L65-E has a deep or shallow pan? Going to replace the filter as I'm sure it needs it anyway, it's cheap, and my dad said I needed to see if there's any metal shavings stuck to the pan plug. Also I've heard RockAuto is a good place to get parts, anyone that can confirm that?