CE Light - Code P0170 Fuel Trim
 

I've recently replaced my air filter and my fuel filter in a '97 C230. I think they were both the original filters. I replaced them with OEM parts from Fast Lane.

The CE light came on a couple of days later and I took it to AutoZone to have the code read. It came up P0170 Fuel Trim Malf. I've looked through most of the posts relating to the same issue. I see most people say it is the MAF meter. I have also seen things about checking actual values, adaptation, vacuum lines, O2 sensors, etc.

Does anyone have a list of things to check systematically to narrow it down to the MAF?

Do you think I need to reset the light (disconnect battery) since I just changed the air filter?

If I can get a list of values to check (and how to check them, e.g. , at idle, 200 RPM, etc) I will go back to AZ and see if I can read the actual values.

Thanks!

No one has responded yet. . .

Anyhow, I have removed the mass airflow meter and cleaned the filament with an electronic parts cleaner. I reset the CE light yesterday. So far so good, but it usually takes a few days to come back on if that's what's going to happen.

If it does come back on, I plan on taking it back to AutoZone and checking the code and attempt to look at some actual values.

Any help in the meantime would be greatly appreciated.

Hi dyazdani,

Guess what. I had the xact same thing happen to me yesterday, The fault codes I got were:

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 don't know why yet, but i'm going to see my mechanic hopefully today. If I fond out what the problem is i'll let you know.

I was thinking MAF too. I hope it fixed your problem as I think i'm going to replace that first too.

Thanks for the reply.

Do you happen to know what kind of reader was used?

I'm not confident that the AZ personnel knew all the features of their reader. All I got was the P0170 code, no actual values or the diagnostic reports.

I found a MAF on eBay for cheap, it was the product of a misdiagnosed problem. If I don't need it, maybe you'd be interested in trying it??

Let me know of your progress.

Same here a few years ago. My lay opinion is the ***** about changing the air filter is to be sure to vaccum out the dust and stuff in the air filter box. If you don't, the dust seems to get past the filter area and mess up the airflow meter. It's expensive and a pain. The meter is very sensitive.

Best,

I know no one (touching wood) that has got the mileage out of their Air Mass Meter that I have. I am (right or wrong) attributing it to my frequent air filter element changing, and VERY thorough cleaning of the airbox with every service.

Many folks that have installed K&N's have wrecked their AMM's so I would guess that (K&N's move more air and more "stuff" too) the AMM is damaged by particles flowing through the device.

When my Dad's 98 C230's AMM went, I found the airbox filthy. His car had codes P0170 and P0171.

There was a bunch of stuff (i.e. leaves, grass, etc) in the bottom of the airbox when I changed the filter. I cleaned it all out very well.

Anyone know how to tell if the AMM is bad? When I looked at it, the filament did not appear to be broken in any way. I'll keep you informed as to if the CE light comes back on in a few days.

Thanks!

The filament is very senstive and I don't think there is a way visually to see any damage. I think the only way is to use the SDS.

Does anyone know if there is a resistance or voltage test for the AMM on the ME2.x systems...?