My check engine light has come on reading, "Check Engine Electronics." I thought it might be the gas cap, so I tighten the gas cap and reset the light by disconnecting the battery, but 3 days later the light reappeared. I got the ODBII reading from Autozone and it is P0170, which they said is the FUEL TRIM MALFUNCTION.</P>


I have read some of the other replies on check engine lights, and some of them say it could be the mass air flow or something like that. Could anyone help me with what exactly is the Fuel Trim Malfunction, and how to solve it?</P>


Thanks so much,</P>


Miller</P>


97 E320 76k miles</P><edited><editID>mbmiller</editID><editDate>38068.805625</editDate></edited>

 

Here is some information on the Fuel Trim Malfunction, ODBII code P0170. I finally couldn't stand the engine light being on, so I took my car to get diagnosed by my mechanic. I tried it myself first by checking for vacuum line leaks, tightening my gas cap, and cleaning my mass air flow sensor, but nothing worked. They also found the same error code as Autozone, and determined it to be a faulty Mass Air Flow sensor. So for anyone who gets an P0170, Check Electronics Engine light, this MAF is most likely the problem. I ended up paying $268 for a new part (Bosch), Mercedes wanted over $500 for it. And it takes only a few mintues to swap it out, very easy to do yourself. Hope this helps anyone else who might have the same problem that I had.

Mbmiller
97 E320 76K miles

BTW, I am trying to get rid of my OEM wheels from my 97, if anyone is interested they are posted on ebay for cheap.
http://cgi.ebay.com/ws/eBayISAPI.dll...ADME:B:LC:MT:1

 

P0170 is a problem about self adaptation of mixture formation to limit values. (was your engine a V-6?)

air leak
diaphragm type fuel pressure regulating valve
engine wear

check all those things too. i have replace many pressure regulator that has an internal leak on it. there are few ways to check it.

i usually change the adaptation value to correct such problem using HHT or Star Diagnosis. also the threshold desensitivity (plus 0.5)

 

My wife 1999 E320 check engine light just came on today, I want to disconnect the battery but can not find it, some where underneath the seat ?

If I have to replace the pressure regulator or MAF, where are these located ?

mbmiller

Have you fix your check engine light after replace MAF

Thanks
TC_SJ

 

it was W210 and not W211

 

tc_Sj,

In my 97 e320, the battery is located underneath the rear seats. There are notches toward the outer portion of the entire seat unit near the door sills. You can pop the seat unit up and out, after you click the notches upward. My battery was under the paper lining on the rear passenger side.

Just remember if you disconnect your battery ... you will need your radio code. It comes on a business card in your owners manual, or you can get it from your dealer with your VIN number. You will need this to reset the radio, just follow the direction in your radio manul on how to reset.

My MAF is located inbetween the air filter and the trottel. It's on the very top, so it's very easy to get to and change. Here is a link and picture of one for a 1999 E320:

https://www.autohausaz.com/catalog/l...Token=60059003

This is where I bought mine from, I found it to be the cheapest place for a new OEM part, but you might want to look around the internet some more. But they were very fast shipping, and easy to deal with.

Just note that it could be other problems, i.e. vacuum line leak, gas cap. I had mine check out, and determined it was the MAF. I bought the part, and it took less than 5 mintues to change out. And it's been over 150 miles, and it seems perfect.

Hope this helps you some.
mbmiller

97 E320 77K miles

 

Hello

Any one know a good shop in San Jose, CA ( Northern Bay Area) that can run diag and tell you what exactly wrong.

I need to fix my wife 1999 E320 with 65 K miles,

May be I just need to order the Air Mass Sensor and replace it see if this will solve check engine issue.

How offten the Air Mass Sensor fail ?, I guess sooner or later ?

Other poeple say could be oxygen sensor ?, I have mix result some car either gas 1 or 2 sensors ?

If I have tocheck for vacum lines leak, can some one point to which section of the car

Thanks
TC

 

if the air mass sensor is faulty, if you notice any the following:

#acceleration is poor and cannot pick up speed like before
#you will hear a popping sound from the area of throttle valve while accelerating at a speed of about 10 to 25 m/h.
#hard starting or engine misfire and shaking.

there is no definite time for an air mass sensor to fail. in some cars, it's faulty before 2000 miles and in others up to two years.

oxygen sensor will cause the "check engine" light to come on also.
you got 4 oxygen sensor in your car, two in every cylinder bank.
2 for the upstream (before the catalytic converter) and two for the downstream (after the catalytic converter)
a substitute value will use by the control unit in case these got problem, but the "check engine light" will come on.

the upstream are usually the first one to get faulty and affect the air-fuel mixture.

the only vacuum leak that you can check is from the regeneration valve which goes directly to the side of the throttle valve.

 

I can not find the notches any where in the rear seat to remove the battery, however I found a plastic cover in the rear seat, I pop it off and there is a big ground cable, I disconnect the ground for 10 minutes and now the check engine light goes away, will see if it's coming back.

My wife is dring the car now, I did not notice any like you stated below since the check engine like came on,may be too early to tell:

#acceleration is poor and cannot pick up speed like before
#you will hear a popping sound from the area of throttle valve while accelerating at a speed of about 10 to 25 m/h.
#hard starting or engine misfire and shaking.


Thanks
TC