Check Engine Light came on: P0460 Fuel Sys1-Open Loop Mode

[kameraguy]

Yup, yet another CEL issue in the repair section

CEL came on yesterday afternoon. Car does not appear to be running bad, or any differently...although the idle is slightly rough.

I plugged in my OBD scanner and found the following info:


ECU #=01

Freeze Frame T.C. -P0460
Fuel Sys1-Open Loop Mode

Short Term Fuel Trim---- 0%
Long Term FT,B1 -------- 6%


MIL is ON, Stored Trouble Codes Present
Misfire Monitoring Complete
Fuel Sys. Monitoring Complete
Component Monitoring Complete
Catalyst Monitoring Complete
Evaporative System Monitoring Complete
Sec. Air System Monitoring Complete
O2 Sensor Monitoring Complete
O2 Sensor Heater Monitoring Complete
Fuel Sys1-Closed Loop Mode

Short Term Fuel Trim---- -1%
Long Term FT,B1 -------- 13%
Cmd Sec. Air Status ---- 4
# of O2 Sensors -------- 2


ECU #=01
MIL is ON
Vehicle Reports 2 Stored Trouble Code(s)
TC1 - P0460
Trouble code definition not found

TC2 - P0170
P0170 Fuel Trim Malfunction (Bank 1)
No pending codes reported


I searched the repair section and found the MAS is usually at fault when a the CEL pops up when the car isn't particularly running bad. However I saw the codes usually attributable to a bad MAS were:

P0171
P0173

It appears my codes are different. I get a P0460 and a P0170.
Could this explain why my fuel guage sometimes fluctuates?

Does anyone have an idea what might be the problem? Anyone else have this?



Thanks!!!

[Eurosport]

P0460 — FLI Fuel level sensor circuit malfunction ---probable causes: Open/short circuit, cluster, tank unit, open case GND

P0460 Fuel Level Unit ___No Change Over Miles No movement of fuel level sender detected.

P0170
Fuel Trim,Bank1 Malfunction

so if you say your guage gives you different readings from time to time
from this info i'm thinking it has to do something with your tank fuel sensor, those do go bad from time to time and mostlikely triggering those 2 codes for the same thing

[kameraguy]

Thanks for the info Euro. I've always had problems with my fuel indicator (as I think many of us do) so hopefully this explains the P0460 code.

I've never had the CEL come on because of it before though. So I searched mercedes shop for the P0170 code, and it appears this is more common than I thought.

There have been several threads on this, and here's a particularly helpful one:

http://www.mercedesshop.com/shopforu...m&pagenumber=1

It seems the MAF definitely may need replacing. I've gathered the troublecode P0170 pertains to the inability of the MAS to set the correct air/fuel ratio. What also needs to be done is to have the shop reset the fuel trim adaptation.

So if you replace the MAS, but still get a P0170, then try having the shop reset this setting in case they did not (or if you replaced the part yourself.

I am hoping this will be all I need. However I am still going to bring my car tro the mechanic just in case. I hope to do this tonight or tommorow.

Fortunately it seems my problem isn't too severe yet (only slight rough idle, unlike worse case issues where the car is hunting sporatically between 500-1500 RPM, or even almost stalling), so hopefully I can get around to my mechanic, which is like 60 miles away

[kameraguy]

I found a more detailed message to P0170:

P0170 - B Self adaptation CTP (idle) at limit (N3/10)


I've also found several other possibilities which would trigger the CEL with a code P0170:

1) 99/100 times it's the MAS.

2) If the MAS is replaced and the code persists, make sure the fuel trim adaptation is reset in the computer. By default the car should take approx 10miles to adapt after the MAS is changed, but sometimes it requires a hard reset if the CEL stays on.

3) Check for possible fuel pressure/vacuum leaks, which can also cause the code (how do they check for this?). I guess make sure the pipes between the MAS and the airbox are snug without play? If so (or to be safe), replace the Air Intake hose.



I never considered looking into the air-intake hose, so i'll check that latter today. Hopefully that is loose or something. I'll also double-check the MAS and see if it is obviously obstructed or dirty.

Man, I hope it's something as simple as that.

[Eurosport]

also if you take off the cover on the engine, check those vaccuum lines as well, they are the white/yellowish if old and they are plastic, i know they could easily snap with age, so just make sure they are all intact.
since you live in cali, before buying anything to repair, get together with another c36 and see if they let you swap the MAS, clear the code, then drive for a few mins, if it's the MAS it won't give you the code again, but if it does then you won't be spending money on a new MAS when it's not faulty to begin with

oh and i hope i don't see that tow truck picture again with your car on it, we'll all have a heart attack

[5.52]

pnsji may have an extra MAS for C36...cheep

hope this helps and good luck with your C36....
5.52

[kameraguy]

Thanks for the tip Fad, i'll e-mail him to see if he still has it for sale.

And as if i'm not already going nuts in paranoia, on my way to lunch the darn CEL goes out. What the...

So I haven't seen the light come back on after 20 miles of driving....odd...

Maybe the MAS is just dirty?

Either way, I might as well replace it.

[pnsji]

Hey Chris, I have 1 that you could try to use.
Do you notice if the idle is fluctuating alot?

[714guy]

Originally posted by kameraguy
Thanks for the info Euro. I've always had problems with my fuel indicator (as I think many of us do) so hopefully this explains the P0460 code.

I've never had the CEL come on because of it before though. So I searched mercedes shop for the P0170 code, and it appears this is more common than I thought.

There have been several threads on this, and here's a particularly helpful one:

http://www.mercedesshop.com/shopforu...m&pagenumber=1

It seems the MAF definitely may need replacing. I've gathered the troublecode P0170 pertains to the inability of the MAS to set the correct air/fuel ratio. What also needs to be done is to have the shop reset the fuel trim adaptation.

So if you replace the MAS, but still get a P0170, then try having the shop reset this setting in case they did not (or if you replaced the part yourself.

I am hoping this will be all I need. However I am still going to bring my car tro the mechanic just in case. I hope to do this tonight or tommorow.

Fortunately it seems my problem isn't too severe yet (only slight rough idle, unlike worse case issues where the car is hunting sporatically between 500-1500 RPM, or even almost stalling), so hopefully I can get around to my mechanic, which is like 60 miles away

this is the same code i have, and my car use to make this popping noises, which was combustionin the pre-cats i think. anyways eversince i cleaned my MAS poping noise went away buut my CEL if still on i haven't reset it yet tho, maybe this weekend i'll try and let you know how it goes.

keep me updated on this tho, i would like to know what else is wrong.

thanks

jason

[kameraguy]

Cool Susanto. I'd like to buy it from you.

As for idle, it isn't fluctuating wildly, but it does fluctuate. For example, when at idle, the needle slowly fluctuates from 500-700 rpm at times. Also, when I drive and come to a slow crawl to a stop-light, the revs fluctuate and feel rough.

I hope the MAS is the culprit.

Can you e-mail me your asking price and when you will be available so i can pick it up?

Thanks!
kameraguy420@yahoo.com


Merry xmas to me! Another damn car repair!!

[pnsji]

It is not for sale.
You could use it to figure out if your MAS is the problem.
If it fluctuate around 200, it is actually pretty big fluctuation.

Jason, you use a liquid to clean it? like rubbing alcohol?

[714guy]

Originally posted by pnsji
It is not for sale.
You could use it to figure out if your MAS is the problem.
If it fluctuate around 200, it is actually pretty big fluctuation.

Jason, you use a liquid to clean it? like rubbing alcohol?

first i removed the sensor then spray it with carb cleaning and then rinse it with brake cleaner, and air it to dry it. thanks to speedybenz.

It worked i guess, no more popping noise. I also took out the little screen cover that covers the MAS which seemed to help i think. the car runs better then before i did it tho.

[kameraguy]

Susanto, d'oh! Fad made it sound like you were selling it...sorry about that!

It's cool man. I don't wanna mess up your backup MAS. Thanks though!

I have a feeling if it is my MAS, it may be due to using a K&N filter. I am hearing a lot of consistency between MAS problems and cars equipped with K&N filters.

Anyone have similar experiences?

[jnolte]

Originally posted by kameraguy
Susanto, d'oh! Fad made it sound like you were selling it...sorry about that!

It's cool man. I don't wanna mess up your backup MAS. Thanks though!

I have a feeling if it is my MAS, it may be due to using a K&N filter. I am hearing a lot of consistency between MAS problems and cars equipped with K&N filters.

Anyone have similar experiences?

Hmm My MAS was messed up on my C36. My filter was filthy tho. I just bought a New OEm filter and MAS from importec.com But it was so bad my car would stall on the freeway and to go you would have to go into WOT or it would just sputter and puttt.

[kameraguy]

Damn jnolte, that sucks. That's a lot worse than my car. That's what i'm afraid of...stalling somewhere unsafe. Well, I hope the CEl doesn't come back on until I replace my air-filter and MAS.

[ryhi]

i have MAS problems too, but my car runs normal....sometimes my CEL turns off...i wonder what was wrong with my MAS..i was told they can only go bad in 2 ways....they get dirty (k&n oil?) and if u redline ur car, the MAS wire can go bad from getting too hot or something

[JRE320]

When was the last time you replaced your MAS? Maybe it's about time to replaced it..

[pnsji]

Originally posted by kameraguy
Susanto, d'oh! Fad made it sound like you were selling it...sorry about that!

It's cool man. I don't wanna mess up your backup MAS. Thanks though!

I have a feeling if it is my MAS, it may be due to using a K&N filter. I am hearing a lot of consistency between MAS problems and cars equipped with K&N filters.

Anyone have similar experiences?

I was selling it, but I decide to use it as backup.

My MAS goes bad after I use K&N for about 6 months
I just don't think if it's a good idea to use K&N with Mercedes.

[kameraguy]

Wise decision. Had I known the MAS was a common item to go out, i'd have a spare handy too

Since when was my last MAs replacement...hmmm...let me see.....uh, probably never At least when I took ownership of the car.

ryhi, same here. My CEL came on, but no noticeable problems with the car....and before I could really stress enough to bring it to my mechanic, the light went out.

All i know is, once I dig up the brand new OEM filter I tossed in my shed, out goes the K&N and a cleaning my MAS will get. I hope that is all that is wrong with my car.

[moebiusgold]

In my opinion there are a couple problems with K&N's. They need a prefilter to keep some of the bigger stuff from laying in the pleats andpotentially sucking through. They are very pourous and lots of small dia. stuff gets trough unless they are very oiled. If you put this much oil on them some of it gets sucked down the intake tract and onto the MAF. People tend to let them get way to dirty. I clean mine every 2,000 miles at the oil change regardless. My C36 will never get one. The 43 has one but it is in front of the drivers wheel inside of the inner fender. and ther is 5 feet of hose before it gets to the MAF. I just replaced MAF at 60K. It was so dirty I don't know how it was working properly. One of the circuts in it died so it didn't matter. BTW dealer discount price was $249.20. Ouch. Stealerships. A big strike against Phil Smart for selling me a "Used" one first. They said they'll make it up to me. Hmm

[714guy]

hey Kameraguy

if the CEL goes on again with the same code, try to clean it the way speedybenz advised to carb cleaner and then brake cleaner. My CEL just went off right before i was about to clear the code and it was about 2 weeks ago when i cleaned it but didn't reset it. Looks like the cleaning worked, took about to weeks for the ECU to recognized it was clean. Hoppefully this will be the last of my problems. Good Luck with your MAS.

[JOESID]

OK, so I am getting P0170 so I'm guessing its the MAF. My car every once and a while will take 3 trys to start, (rarely) is this possibly from a bad MAF? Other than that I have not noticed any other odd behavior.

[jnenad16]

Originally posted by JOESID
OK, so I am getting P0170 so I'm guessing its the MAF. My car every once and a while will take 3 trys to start, (rarely) is this possibly from a bad MAF? Other than that I have not noticed any other odd behavior.

P0170 - fuel trim (bank 1)
this could be a number of things, from a vacuum leak, to O2 sensors and the MAS.

nenad

[hvmercy]

BUMP!

Bringing up a 7 year old thread.

My niece's 97 C230 is getting P0170 and P0460 error code.
Mass Airflow sensor is about 2 months old.
Fuel level sensor is 6 months old.
Fuel filter is also 6 months old.

I erased the error code last night. She drove it to work this morning without problems.
I just asked her if the Check engine light came back on. She said no.
Her commute is 30 miles each way so that should be enough to find out if the CEL will come back on.

I plan to spray the MAF with MAF cleaner tonight (for P0170 error)

What do you think is the culprit on the P0460 error code?

Thanks in advance for your help.

[hvmercy]

SOLVED after cleaning mass airflow sensor, replaced fuel filter & fuel level sensor relay.

I say she'll be trouble free once again.