Boost&Cubes

Folks:

Would like some debug help and advice.
The wife's ML430 "Check Engine" light has been coming on and turning off intermittently over the last few weeks between starts. Sometimes the light comes on immediately after startup, other times after running a while. Then after a few more startups a few days later, the Check Engine light stops.

So I decide to buy a OBD2 scanner.
The scanner shows the following Diagnostic Trouble Codes (DTCs) -

P0130 O2 Circuit (Bank1, Sensor1)
P0150 02 Circuit (Bank2, Sensor1)
P0170 Fuel Trim (Bank1)
P0173 Fuel Trim (Bank2)

It doesn't seem likely to me that both O2 sensors would be going out simultaneously.
So my question is could this be pointing to the MAF instead ?
Advice or help on what next to try would be appreciated.

Thnx,
Boost&Cubes

vettdvr

you didn't state the mileage but I have found O2 sensors will begin to fail about 70,000 miles. My first guess would be to change the O2 sensors. If the car has 70,000 miles they are tuneup repair parts and part of normal manitenance. I would just replace them (4) in most cases as part of normal manitenance and see if that corrects the problem. The MAF is not a routine tuneup part and will cost much more than the O2 sensor.

Jim

Dsmed

I would go after the air mass. O2 sensor don't have a average life some go bad after 20k miles some go 150k miles. O2 are not a part of regular maintenance. Two o2 sensors will cost about the same if not more that a air mass sensor. If your car is less that 8 year old and has under 80,000 miles go to the dealer and mention to the the 8/80 warranty. Catalythic converter, o2 sensors, ECU are covered for 8years or 80k miles, government regulations.

Ausmbtech

Change the air mass meter and all should be fine.

benz-tech

wrong, MAF.

Boost&Cubes

Many thanks for the advice and replies.
It seems that the consensus is that my MAF is going out.
Right now the Check Engine light is off and I'm not getting errors from my scanner.
But I guess I should order a replacement MAF as it's matter of time ?

Thanks Again.

mleskovar

[QUOTE=Boost&Cubes;2422505]But I guess I should order a replacement MAF as it's matter of time ?QUOTE]

Try cleaning it first. Quick and easy.

C32AMG/02

To analyze the problem you just have to get the adaptation numbers and codes. You are exceeding a limit. The problem varies by what limit you are exceeding. You will need a scanner that can read Data stream parameters

C230 Sport Coup

That mean the StarDiag system correct?

Taiwanese

Anyone knows how many oxygen sensors in a 98 E320?

Thanks.

C32AMG/02

[






QUOTE=C230 Sport Coup;2426823]That mean the StarDiag system correct?[/QUOTE]


A lot of independent shops have PC SDS. There are other soft ware, Non
MB that can read Data parameters

The most important information IS the fuel adaptation LEAN or RICH numbers


Possible causes of Lean Fuel trim adaptation
Plugged fuel filter, fuel pressure or fuel regulator, in some models the regulator is part of the fuel filter, vacuum leak (false air), did you do any work on the engine, defective fuel injectors or MAF

Possible causes of Rich Fuel trim adaptation
High fuel pressure or vacuum-controlled fuel pressure regulators leaking diaphragms,
Leaking fuel injector or MAF

A long term fuel trim value of + or - 32% means the ME has reach its correction limit, Defective MAF. Once you correct the problem you must reset the fuel Trim adaptation values.

Dsmed

Taiwanese
There are 4 O2 sensor in a 98 E-class.


The adaptation data will start to zero out after about 3 miles of driving by itself. That will tell you that the air mass sensor fixed the problem

Taiwanese

Dsmed,

Thanks.

CFLPEEK

if both or one of your cats are blocked or bad, they could send erroneous values to your 02 sensors. this will be really loud, and probably illegal where you live, but disconnect the cats and drive it around and see if the light stays off. if it does, then your cats are bad and they will either be covered by the ml cat campaign, or the 8/80 warrenty. you did say you had an ml, right? the cats go bad on those all the time

vettdvr

IMO.. this is the issue.

RogueMBtech

Dont forget to replace air filter when you do the air mass.

Boost&Cubes

Folks:

Thanks to everyone for their advice and help.
Our ML has 98K miles.
I first tried cleaning the MAF, but the CEL kept coming back on the next day after clearing them with the OBDII scanner.
So I replaced the MAF.
It's been 3 days and so far, so good.
Also, the air filter was recently changed as well.