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Discussion Starter #1
Running a Edge Evolution on stock LMM on level 2, towing mode. I pull about a 12k lb toyhauler and if I get into it some like trying to accelerate up a large hill the truck will go into 'reduced engine power' and throw the code. I can clear the P0101 using the tuner and its normal until I get heavy foot again.
Monitoring the MAF g/s on the tuner I see about 25 at idle and it can go over 400 at large boost.
Running a stock style paper filter, can't remember the brand but maybe WIX. MAF has been cleaned (is brake cleaner a no no?) but not replaced. Fuel filters are replaced on recommended intervals and the oil more often. 99k miles and stuck on this problem I've been fighting all year, any suggestions?
 

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There are lots of threads on the P0101 code to give you some insight on a fix if you use the "Community Search" box located at the top of the screen

(y)
 

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Discussion Starter #3
Yep, been reading them all year. Thought it was time to post my specific situation.
 

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Brake cleaner on a MAF is definitely a big no-no. I've seen it eat plastics and definitely paint before. CRC makes a MAF cleaner, just about every parts store carries it or some brands version. You might have caused some damage doing that.

635516
 

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25 gm/sec is quite low. Should be up near 40.
 

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Discussion Starter #6
Not sure why it's so low at idle when it seems to be working fine under driving conditions. Just flooring it from 20 up to 60 mph it just squeaked over 400. Should it have gone higher there also?
 

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I would replace the MAF
 

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One thing you could try is to remove your paper filter, then measure MAF and see if there is a large difference in the result at idle. If your filter is too restrictive, that could explain the low result.
 

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Discussion Starter #9
Pulling the filter sounds like a easy test. Thanks for the idea.
 

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It's the EGR valve. You can take it apart and try to clean it. I'm about 30% at cleaning solving it. The other 70%, I end up replacing the EGR valve. The problem is that it is not seating fully closed. That's why the idle flow number is low. "Air" is entering from the EGR, not just the air filter.

When removed, both valve seats should be closed (seated).
Only other issues I've had is the plastic intake tube at the turbo has been loose (the v clamp) or, the resonator clamp is loose.

If the EGR is partially open (even as low as 3%), you'll get the p0101.
If the EGR system (valve or cooler) is plugged, you'll get a p0401.
Now, mind you, this is all from memory. I sold my last LMM 3 years ago, and the issue was much earlier than that.
 

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Never thought about the EGR being the problem. Hope the OP is able to fix it.
 

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Discussion Starter #12
So this morning I went to pull the filter and check the g/s reading but first I started the truck to check it and it was at 39 g/s. Idle didn't seem high I figured since it was cold start I'd check it when I got home. So when I got home tonight it was actually reading 15 g/s. I pulled the air filter and it only went as high as 15.2 g/s. Pretty low but it is consistent. I'll buy a can of cleaner and see if it helps but it's starting to look like a new MAF.
 

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Discussion Starter #13
It's the EGR valve. You can take it apart and try to clean it. I'm about 30% at cleaning solving it. The other 70%, I end up replacing the EGR valve. The problem is that it is not seating fully closed. That's why the idle flow number is low. "Air" is entering from the EGR, not just the air filter.

When removed, both valve seats should be closed (seated).
Only other issues I've had is the plastic intake tube at the turbo has been loose (the v clamp) or, the resonator clamp is loose.

If the EGR is partially open (even as low as 3%), you'll get the p0101.
If the EGR system (valve or cooler) is plugged, you'll get a p0401.
Now, mind you, this is all from memory. I sold my last LMM 3 years ago, and the issue was much earlier than that.
I'll be checking this out too. Thanks.
 

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So this morning I went to pull the filter and check the g/s reading but first I started the truck to check it and it was at 39 g/s. Idle didn't seem high I figured since it was cold start I'd check it when I got home. So when I got home tonight it was actually reading 15 g/s. I pulled the air filter and it only went as high as 15.2 g/s. Pretty low but it is consistent. I'll buy a can of cleaner and see if it helps but it's starting to look like a new MAF.
That certainly could be your problem, but it also could be the circuit for the MAF. Make sure you have a 5V reference input to the sensor and a good ground. Check the reading when it is in the 15 range, not 30+ range. You want to check when the problem is occurring.
 

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Discussion Starter #15
Current plan is to buy a can of cleaner on my way to work and see if that helps at all. Then I was going to check the voltage. Sure appreciate the pin schematic Ron attached saving me the time of finding it. Wish I had a scope to check the ground for noise. I think ignition voltage of course should be near 12V and MAF sensor voltage should be 10V. The IAT signal I think is a square wave that I won't be able to test. Does that sound right?
 

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I'm getting old. MAF power, pink wire in the center of the connector, should be battery voltage, not 5V as I posted. Most sensors are 5V, but this one isn't.
 

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Discussion Starter #17
Well using MAF cleaner didn't change anything. I'm still reading 14.2 g/s in park at idle. Pretty steady, only varies about +/- 0.3. I'll be checking the voltage levels next.
 

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Discussion Starter #18
Over the last few weeks I watched lots of YouTube videos on this problem and all of a sudden yesterday I saw 4 videos that all said the quickest way to test MAF is start the engine and pull the MAF connector. If the engine stops the MAF isn't the problem. If the engine continues to run replace the MAF. This sounds backwards but after talking to my neighbor who likes to build cars it's a little clearer. He tunes the LS motors to run without a MAF at all because the MAP sensor is more important for tuning. It seems if a MAF is failing the engine can default to MAP & TPS. So when you disconnect MAF it doesn't matter. So I tried it and the engine continued to run fine. I really don't know the technical side here but I'm going to go ahead and order the MAF and hope that solves it.
 

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Your neighbor is just converting them back to a speed density system (80's technology) where the computer has to rely on a lookup table to "guess" airflow based on those inputs. Your truck is doing the same thing when it senses a problem with the MAF. It works, but much more efficient when you set fuel delivery off the actual known airflow. Which is why pretty much every vehicle has a MAF these days.
I would still look at the EGR too like heymccall posted, if its gummed up it could be causing the code problem. Especially since your code occurs only at or after WOT.
Replacing the MAF is a good idea still since theres no way of knowing if the brake cleaner did any damage to the circuits on it.
 

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Discussion Starter #20
That's a good a better explanation than I could have ever made. The new MAF is on order so I'm in a holding pattern right now. The truck runs fine around town so no rush. I'm actually shopping for new trucks or I'd be cleaning the EGR just for maintenance. I'm not really liking the new octagonal styles fenders on 2020 GM trucks.
 
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