L5P Duramax P0101

Andrew Technician De Motte, Indiana Posted   Latest   Edited  
Case Study
Driveability
2017 GMC Sierra 2500 HD SLE 6.6L (Y L5P) 6-spd (1000)

This truck belongs to one of my really good fleet customers. I personally have not had to do anything to this particular truck for the past 35000 miles. Just been to the lube rack for oil changes, fuel filters, and rotates. Last week they brought the truck in for an oil change, rotate, and fuel filter. When my service writer went to pull the truck out of the stall he noticed the check engine light on. My shop is separate from the main shop. I have 4 bays in what was the old detail center just for my diesel and transmission work. As he was pulling the truck around he said he felt like the truck was low on power. I was buried up to my nose with 3 transmissions apart and a cab off of another truck doing a EGR bypass valve. I quick scanned the codes and noticed it had a P0101 MAF Performance. The oil change kid came running over saying "I may have caused the light" At this point I ASSUMED that they keyed the truck up with the MAF unplugged checking the filter. I checked to see if the customer had time for a quick diag and was told they were in a hurry, the owners wife brought it in and she had errands to run. So I cleared the code and the writer pulled the truck out of my bay. This whole ordeal took about 2 minutes. I want to stress, this happens at my dealership ALL the time. Nothing new, I have become numb to this.

About an hour later the wife calls the shop and says the truck barely got out of it's own way while she was pulling out in traffic. She wants to schedule the truck in for a full diag. A few minutes later her husband calls the shop to talk to me personally. (this is pretty standard with this fleet, all of their diesels come to me and we have a great relationship sometimes it is just easier to talk to the person) Long story short they requested the fuel filter during the oil change due to his check engine lamp and lack of power. It's at this moment I realized I made a mistake not looking at freeze frame data to see how long the fault had been present. Ok, we will proceed when the truck comes back in.

This particular fleet is a excavating company. So they are always in a hurry and always had scheduling issues. Fast forward to today and the truck shows up. I verify the lack of power concern in the parking lot. I did not even have to drive far. I pull the codes and the P0101 is current. Now I will tell all of you guys from experience here recently, I know exactly what the problem is. But I want to share with all of you the fault and what happened

process​.​filestackapi​.​com/resize=h:1000… as you can see the P0101 is current.

process​.​filestackapi​.​com/resize=h:1000… At idle the MAF is reading 12 G/S in this snap shot

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At idle MAF is reading around 7 G/S

I told you I knew instantly what was going on right? Let me give you guys a little heads up if you have no seen the new hood designs on the … GM trucks with the L5P the hood scoops are functional. They direct right to the airbox on the passenger side (I am sorry I did not take a picture today) . On the driver side there is a hood drain. And just like with a evaporator drain they can get clogged up. And then the water has nowhere to go but inside the air box. Very bad design on the L5P's, in my opinion. So what happens is the air filters get water logged and suck them selves in. process​.​filestackapi​.​com/resize=h:1000…

As you can see with this one. The biggest issue I had with this is my oil change guys SHOULD have caught this. Probably a while ago. The filter had not been changed since new. And most likely not inspected in a few changes. I felt it was important to share with you guys that this truck is an excavating companies truck, it gets but through hell and in all types of terrain.

https://process​.​filestackapi​.​com/resize=h:1000…

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Obviously what the filter should look like. I used this as a teaching tool for my lube rack kids. They will now remove the drains on the hoods on these engines from now on during service and make sure they are clean.

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These pictures show the drain installed and removed. They simply twist on and off. These trucks now have a note in the system as well the owner wants the filters changed at every service. I have seen these particular trucks have issues with air filters as quick as 500 miles. They have set MAF, DPF, BOOST, Regen codes in the past as well. Also a L5P will normally run 17-18g/s at idle with a new filter and no CAC leaks in my area. I should have posted a data pid of after the fix, I am sorry for that.

+10
Mario Diagnostician
Weston, Florida
Mario
 

I'm sure that kid won't forget that lesson. Interesting that the kid would alarm you about setting off a MAF code for checking an air filter that he supposedly checked, unless I'm misunderstanding. Also funny that you mentioned this issue to Matthew Shanahan's post. Thanks for sharing Andrew. I don't work on diesels but this is a good thing to archive into the mind.

+1 Ð Bounty Awarded
Andrew Technician
De Motte, Indiana
Andrew
 

No, you understood correctly. 2 issues, 1 he lied 2 he only "checked" meaning he pulled the top part of the box back and nothing more. I mentioned this to Matthew because I was actually working on the truck at that moment. It seems to be a pretty common issue around here anyways. This is probably the 4-5th I have done in the past month. The other thing I should have noted is I have seen

+2 Ð Bounty Awarded
Bill Technician
Rosetown, Saskatchewan
Bill
 

I have yet to get an L5P in the bay. Do they still give you an ALER PID? I am assuming so. I can't wait to start building a data base.

0 Ð Bounty Awarded
Andrew Technician
De Motte, Indiana
Andrew
 

Yes the ALER is still there... Wait until you see the next L5P case study I am working on. This truck was/is very challenging. I will tell you I struggled for a bit to decide if it was trans or engine related. I know most of you Indy guys are not seeing these particular 6.6's yet. But I have always felt diesel diag training is lacking, and I am hoping to arm you all enough with what I see to

+2 Ð Bounty Awarded
Bill Technician
Rosetown, Saskatchewan
Bill
 

That sounds real good Andrew, I look forward to it! Your case studies look good. They look like you are getting geared up for a training career. How many guys from your area do you suspect will be modifying their trucks calibrations now that the cost to play has gone up so much?

0 Ð Bounty Awarded
Andrew Technician
De Motte, Indiana
Andrew
 

I would love to eventually. I do not think my technical or soft skills are to that level yet. And went from being a driveability/emissions guy to now do 75% diesel and transmission repairs at the dealer. I know how long it has taken me to get comfortable working on these systems and if I can shed some light on them for even 1 person, then I feel I made a small contribution to this "family"…

0 Ð Bounty Awarded
Tyler Technician
Hammonds Plains , Nova Scotia
Tyler
 

Yup thats a tough sell. A good customers 2016 Ram eco diesel has been eating coolant for a bit. Going through the egr cooler. EGR cooler is 2800$ before labor. Truck is 10k kilometers out of warranty. He opted to delete egr system and dpf for around 2000$.

0 Ð Bounty Awarded