I have had some trouble with CEL for a few months. It flashed over a year ago, P0170 and P0173 came up, and local dealer tech told me I needed both rear O2 sensors. I lost confidence, cleaned the MAF, and had no problems for some time. In the past two months, CEL is back on, cleaned MAF again, but problem returned. I noted freeze data from my code reader and it seems that I may now need a new MAF. I hope the data below will confirm my guess, or another solution can be suggested. I have a few questions (most of the “newby” type) for the oracles, if they will indulge me:

What is the difference between FT 1, 2, 3, 4? Related to O2 sensors?

What is KPA units for data reported for MAP/ MAF?

How can I “reset” the ECU to begin the relearn process?

The STFT 1 and 2 seem within reasonable range and LTFT are at/outside the limits – does this indicate a recent change in conditions (MAF out of range)?

I already checked for vacuum leeks using the old starter fluid method – no leaks

The P0130, P0150 seem to be related to the MAF errors, based on other threads, any comments?

Thanks for any input – I’m at my limit of experience and knowledge


Freeze data from Actron CP9175

Date 7/15 7/17 7/19 7/20 7/21

Codes 170,173 170,173 170,173 170,173 170,173
130, 150

RPM 1875 600 575 575 550

Load 40.7% 22.7 23.1 23.1 23.1

MAP(KPA) 74 43 43 45 44

Coolant Temp 181 186 186 183 186

STFT 1 2.3% -1.0 -3.4 0.0 0.8

LTFT 1 28.9% 30.4 31.4 29.6 33.5

STFT 2 1.5% 0.8 -3.4 0.7 -1.0

LTFT 2 29.6% 31.2 32.0 30.4 34.3

STFT 3 -100.6 -100.6 -100.6 -100.6 -100.6

LTFT 3 -100.6 -100.6 -100.6 -100.6 -100.6

STFT 4 -100.6 -100.6 -100.6 -100.6 -100.6

LTFT 4 -100.6 -100.6 -100.6 -100.6 -100.6

MPH 43 0 0 0 0

Fuel Sys 1 Closed Closed Closed Closed Closed

Fuel Sys 1 Closed Closed Closed Closed Closed

Chassis/Model???????????????

The car is an '01 e320, 210 chassis.

Again, thanks for your assistance.

The data was badly formatted too. Here it is in clearer format:

five events' data

Codes: P0170/P0173 on all, 4th event also had P0130/P0150

RPM.......1875.....600.....575.....575.....550

Load.......40.7%....22.7....23.1....23.1....23.1

MAP(KPA)74.......43.......43........45.......44

Cool Tmp.181......186......186.....183......186

STFT 1....2.3%....-1.0......3.4.......0.0......0.8

LTFT 1...28.9%....30.4....31.4.....29.6....33.5

STFT 2....1.5%.......0.8......3.4.......0.7....-1.0

LTFT 2....29.6%.....31.2....32.0....30.4....34.3

STFT 3...-100.6 for all events

LTFT 3....-100.6 for all events

STFT 4....-100.6 for all events

LTFT 4....-100.6 for all events

MPH........43.............0...........0.........0.........0

Fuel Sys 1 - Closed for all events

Fuel Sys 2 - Closed for al events

Looking at the data...you need an air mass sensor..new Bosch, not reman or VW insert.

No resetting on that ME 2.8 version. Repair & drive for correction.

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Thanks for your conclusion. I ordered the new MAF and will install on Wednesday. With the replacement part on it's way, i cleaned the old one, and disconnected to battery for 30 min. Now have a P0100 pending (I didn't start cleaning until I had the order confirmed). Problem will be solved in 48 hours.

Curious: is KPA on the scanner kPa (thousand Pascal), where 100 is equal to 1 atmosphere (bar)?

It seems that Fuel Trim 3 & 4 do not correspond to anything in ME 2.8 and are not diagnostic values. Am i close?

I thought a Phd would help to understand these systems. By your moniker, I now realize it is required.

Doc,

Just saw your comment about no VW insert....uhh why? My tech recommended doing that in my 113 engine/SL500. I didn't, by the way, but opted to try the CRC MAF Cleaner which for the past 6 months apparently did what it's supposed to. But, back to the insert...why not the VW?

Thanks,

Bob

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Bob Jones
Bradenton, FL
'87 560SL-Sold
'99 SL500 For Now

How do you do a VW insert? i thought MAF were engine specific?

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New MAF in this afternoon. All problems resolved. Thanks for your review of the data and advice.

I drove about 25 miles with the new one in and the ol' E320 feels better than I can recall.

Installing a VW part designed for a small displacement on a larger displacement MB engine is crazy!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
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Doc,
Don't be so bashful...tell me how you really feel!

Thanks for the reply...VW insert didn't make sense to me, but wanted an expert opinion.

Bob

__________________
Bob Jones
Bradenton, FL
'87 560SL-Sold
'99 SL500 For Now

I am happy to report that the $127 MAF sensor insert from germanstar.net has cured my P0170 CEL problem. To my pleasant surprise, in addition to the elimination of the annoying CEL, the car now has MORE POWER, it shifts smoother, and up-shifts quicker than with the old sensor. With the original sensor 0-60 mph took about 12-14 seconds. Now it is 8-9 seconds!. (This with transmission in regular "drive" mode", both cases). After resetting the old sensor (battery disconnect) the CEL would re-appear within a day or two. I have been CEL-less for over a week with the new insert. Too soon to determine effect on gas mileage.

I bought the car (1997 E320 sedan, 70k miles) used in 2004, and the CEL appeared soon after the purchase. For a variety of reasons (expensive MAF, not certain the MAF was the cause, car ran "good-enough", the CEL tripped only when coming to a stop after driving at freeway speed - a transitory problem, good mileage 20-24 mpg) I resisted buying the complete MAF unit. Even $270 for the MAF assembly seemed a poor bet, not knowing for sure that the MAF was the true culprit. I scoured this and other forums looking for knowledge and cheap fixes. Searching for vacuum leaks, cleaning the sensor with MAF cleaner, blocking the charcoal canister (virtual vacuum leak), new air filter, plugs, wires, etc. Nothing worked. (But thanks to the posters for the advice nonetheless -- educational!)

It was just a few weeks ago that I discovered (in benzworld.org forum) the availability of the MAF insert from germanstar.net. $127 was a relatively attractive bet. It has paid off in spades! Here's a big THANK-YOU to the poster steering me to germanstar, and to all others posting on this topic

Hey buddy is the insert available for any other models such as W202 C220? let me know, thanks

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My Cars
Mercedes CLS
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R.I.P.
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here is the link to the germanstar MAF insert page, I don't see W202 C220 there.

http://germanstar.net/MAF.htm

Just to jump in here: About six months ago I replaced the MAF sensor with one from a local auto parts store - I assume it to be reman, though it does say Bosch on the side. I wouldn't know what it came out of originally.

Now Christy is pulling P0170 and P0173 again.

Could it really be the MAF sensor, again?

This, on my 99 W210.

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Las Vegas NV

I would try a $5 can of CRC MAF cleaner first. I bought mine at NAPA...still running strong and no P0170 code.

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