Hi all,
i have a 2010 GL450 (had it for 3 years, 120,000 miles and its been flawless), this past weekend the serpentine V belt shredded while out driving (i stopped immediately and got it towed home). I replaced the belt, 2 idle pulleys and the tensioner.

Have done 15 miles since the above and just got the check engine light. Code P0172 came up.

Should i first start by cleaning the MAF ? or is there a reset that has to be done ?

Thanks for any suggestions.

 

The generic application of P0127 is “intake temp is too damn high”.

your intake is on the back of the engine towards the firewall so i don’t think your belt shredding episode affected the intake, but maybe knocked a hole in the air box over the exhaust manifold so now it sucks hot air?

 

Or forgot to reconnect the fresh air intake tubes?

 

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You can edit your posts.

Do yourself a favor: Never just post the code. The only thing worse than that is only citing the check engine light ("CEL ON HALP NAO!!!!"). Use your code reader to tell you the code and its meaning.

You should also look at the pending codes.

The MAF sensors don't last forever. The crankcase ventilation is right there, too, burping all kinds of sticky fumes. It would seem like cleaning the sensor would help, but I haven't heard of anyone enjoying a semi-permanent fix from doing so. It's a relatively cheap part, and you can also ensure that its connection to the intake manifold, and how the air cleaner housing seats on it, are all tip top. I applied silicone grease to those rubber interfaces, by the way. Also to the little rubber bumpers on top of the intake, that the housing sits on.

It is possible the MAF gets gunked by the crankcase fumes, and also gets dirt from a mis-seated air cleaner housing.

If I were you, I would clear the codes and watch for recurrence. If you get further fuel system codes, change the MAF. I wouldn't bother cleaning it unless I had reason to believe it was dirty, and unless I happened to have a can of MAF sensor cleaner sitting around. I cleaned mine, and it only bought me 6,000 miles.

 

Thanks, appreciate the reply. I did indeed use a code reader but in the time it took me to walk from the garage (after reading the code) to typing the message, i simply got the last two digits mixed up, that was all, genuine mistake. I have some MAF cleaner so will give that a try first and monitor the code, thanks again

 

I'm the king of stupid little mistakes. Trust me we've all been there.

The reason it's a good idea to quote both the code and its meaning is that it's a data redundancy. Thus the digit interchange doesn't scramble the message. The worst that would happen is someone would reply "U retard, 0127 isn't a fuel rich error"

If you're going to clean the sensor, clean the whole mess. Oil accumulates where the rubber elbow meets the intake manifold. Make sure everything is seated nice and cozy. If the air cleaner housing is not reinstalled properly, the MAF sensor housing and elbow can be dislodged, leading to dirty air leaks and and and. If I were to do it again, I'd be tempted to seat the elbow in Permatex Black; MB has a fetish for weak oil containment, such as cam housing plugs that are loosely friction fit in the hole and the power steering reservoir seal.

Good job on the belt and pulleys, by the way. I just did that on a preventive basis and was grumbling that I was wasting my time and money because the parts I pulled looked tip top. You are the first direct report I've seen of failure. Did you find out what component failed? Did a pulley seize?

 

I'm pretty sure the top idle pulley must have seized, the one with the plastic grooves, it was melted and very little left of it! First i knew there was a problem was at the end of a 120 mile trip, i noticed the steering was very hard to move, i pulled over and saw very little of the belt left and the melted pulley.

 

Aye, that's the component people have called out as the likely one to seize. Sorry it hit you on a road trip, but from the sound of it, you were close to home, which is fortunate.

There is also a thread on keeping a shorter belt on hand should the AC compressor clutch and/or pulley seize. You bypass the AC compressor and can continue on your merry way.

Check out my thread on preventive repairs. People contributed some good stuff.

Welcome to the forums. There are a bunch of good guys contributing here.

 

Thanks, will check out the thread! i try not to hang out here as i tend to think I'm tempting fate!! lol

 

I know the feel.

Honestly, though, I don't know if it's Stockholm Syndrome, but - I've now driven my truck 130k miles, and after an initial period in which I vowed revenge, I came to realize, as I've often quoted forum member alx: That truck ages well. It's hard to define, but if you care for it right and keep your cool when stuff goes wrong, that truck holds up remarkably well. 170k miles and it just purred on my last road trip. I really don't want to put a bullet in that ol' girl's head.

 

Replaced the MAF with a new one this morning, will see how she runs over the next day or so.

 

Keep an eye on pending codes. If you don't already do so, the Torque app on your phone, paired with a bluetooth adapter, is outstanding for monitoring.

 

Well the check engine light came back on after driving 40 miles, i read the codes and i have a P0172 & now P0175 codes, both mean the same thing just different banks.
I do have a Bluetooth adapter and have been using the ODB fusion app, however i don't know what many of the readings should be or mean! i have seen that only the O2 sensor 2 is showing data and not o2 sensor 1 ! not sure if 1 should be showing data ? im not getting an O2 sensor fault code at all.

 

Torque gives you the quick definition of the OBD codes. You have to dig deeper to really understand, though.

Welcome to the fun world of the fuel injection management system. There are two fundamental parts to the system: the MAF sensor and the upstream O2 sensors. The MAF sensor gives the ECU an estimate of how much air is going in, which translates to how much fuel to squirt in, and the upstream O2 sensor gives the ECU data on how much oxygen remains in the exhaust after combustion, which is used to fine-tune the mixture. If the oxy sensors get oxygen data that is outside the range for which they are supposed to adjust, you get an error.

There are also oxy sensors after the cats, but all they do is check that the cats are consuming enough of the remaining oxygen. These are the downstream sensors, aka S2. B1S2 is the bank 1 downstream sensor, etc.

An installation leak after the MAF sensor would result in a mixture too lean, but you might want to recheck your MAF sensor installation anyway. Most of the failures I can think of result in a mixture too lean, not too rich. Clogged fuel injectors, for example. One possibility cited, which I've never heard of for this motor, is the fuel pressure regulator sticking, yielding too high fuel pressure delivered to the injectors.

Is it possible you installed a bad MAF? Crazy, but ...

Would the tumble flap being stuck in the swirl mode lead to too-efficient combustion? Had MB fixed the tumble flap problem by 2010?

There are no other codes, including pending?

It could be failures of the S1's, but that would be one of the last things I'd investigate. With a medium tool like the MBII, you can check the oxy sensor adaptations. it would be a bit of a coincidence for both to go out at the same time.

 

Thanks for the detailed explanation, i guess the new Bosch MAF could be faulty but i doubt it, it is new,lol
I'm installing new air filters today (routine maintenance anyway), I'll double check the new MAF install and everything around it.

No other codes pending, first code I've had come up in 3 years of owning it. I guess its just coincidence that the codes came up 30 miles after she shredded the serpentine belt and i replaced it.

 

Don't get too hung up on the coincidence. If there is a connection, it could be very subtle. For example, I have a leaky valve stem seal. The truck burns oil. However, on one road trip, it mysteriously burned no oil. It took me a while to figure it out: The valve stem seal must be on the intake; I was towing a trailer and had wider-open throttle, so there was less intake manifold vacuum, so less oil getting sucked in past the seal.

You could have an intake manifold vacuum leak. However, everything you've fiddled with is upstream from the throttle, so ...

It could also be clogged fuel injectors. If they make a coarser spray, you will get less complete burning = more oxygen. It couldn't hurt to run some fuel injector cleaner. If you're feeling brave, you can fairly easily pull the injectors and spray carburetor cleaner through them; there is available a gizmo that applies 12V to hold the injector open while you spray. Alternatively, you can buy some high PEA fuel system cleaner; add it to a low tank, slosh it around a bit, and leave the truck idling for a couple of hours. Forum member alx told me they do a "hot soak" method in the shop, which I guess means run to full operating temperature, let sit, shut off, etc. I reckoned it wouldn't hurt much to leave it idling; I monitored the cat temperatures, which remained very well behaved. Deposits on your intake valves would have the same effect and the same cure.

So your connection to the road trip might not be the serpentine belt but rather bad gas you bought along the way.

Edit: Crap, I keep getting confused between too-rich and too-lean errors. Possibly clogged fuel injectors dribble a little gas while shut? I see vacuum leak cited as a possible cause, which is why I mentioned it, but I can't understand how that would work. Too-rich = too little oxygen. My ideas above pertained to too-lean.

Anyway, it couldn't hurt to give the fuel system a little TLC.

 

So i changed the air cleaners, took the MAF off, made sure all the seals were good and replaced it making sure everything was seated well, ran a bottle of Chevron, Techron plus fuels system cleaner through and I'm 100 miles in and no check engine/ codes have returned Knock on wood.
Thanks again for the info and advide

 

November papa.

FYI, the active ingredient in Techron is PEA, and there are cheaper sources of it than Techron. Threads on bobistheoilguy talked about it. You wouldn't believe what people can uncover.

 

Thanks, i read up on the additives briefly and the above was quoted as having the most PEA in it, 32% i believe. It was only $7 for a bottle on Amazon and it did the job

 

Chevron is pretty secretive, but frankly at under $10 a bottle it's not like anyone is going broke either way.