Mechanics

ENGINE DIAGNOSTIC INDICATOR/CHECK ENGINE LIGHT LIT UP

2001 Mercedes Benz C200 • 77,900 miles

Hi,
I purchased a Mercedes Benz used car back in Sept 2011 (C200K W203)
I have driven 600 miles since the purchase and the Check Engine Light has come on 3 times.

On each occasion, I quickly connected the OBD2 reader to my car and it gave me a single DTC code - P0101 "Mass or Volume Air Flow A Circuit Range / Performance"

The OBD2 reader also allowed me to collect and record "live data" (total of 60 frames) whilst the engine was running and the following are the results of 1 out of 60 frames

DTC_CNT = 1
FUELSYS1 = CL_FAULT
FUELSYS2 = N/A
LOAD_PCT (%) = between 18.0 and 23.1
ETC = between 72 and 84
SHRTFT1 (%) = between -5.5 and -1.6
LONGFT1 = 0.0
RPM (/min) = between 740 and 761
VSS (km/h) = 0
SPARKADV = between 14 and 15
IAT = between 27 and 29
MAF (g/s) = 3.42 and 3.74
TP (%) = 4.3
AIR_STAT = no results
O2S_B1S12--B2S----
O2B1S1 (V) = between 0.110 and 0.570
SHRTFTB1S1 (%) = between -0.8 and 0.8
O2B1S2 (V) = 0.455
OBD = EOBD


The Check Engine Light seems to come on everytime I drive long distances at high speeds.

For example, if I drive 30mph to my parents house which is about 2 miles away from my house, there is no problem.

However, if I drive at 70mph to London Heathrow Airport from my house which is 23 miles apart on the highway/motorway, the light comes on.

With this pattern of my driving, does this give you an idea what is the root cause of the problem?

Please note that I had previously had the O2 sensor replaced as it was believed to be the source of the problem. However, this has not been the case since the Check Engine Light has come on at two occasions since replacing the O2 sensor.

Any feedback would be much appreciated

Thanks and regards

Tony
Avatar
Tonyho8
February 22, 2012.



I know the USA models had electrical problems, not one of the best years to own. But the - fuel trim shows the MAF is probably the problem.

Merlin2021
Feb 23, 2012.
Thanks merlin2021.

Fuel trim is a new term for me. I assume you are referring to the following figures when you mentioned Fuel Trim?
>SHRTFT1 (%) = between -5.5 and -1.6
>LONGFT1 = 0.0
>SHRTFTB1S1 (%) = between -0.8 and 0.8

Should the above parameters need to be in an ideal range if the car is in good condition? If so, what is the ideal range?

>MAF (g/s) = 3.42 and 3.74
Also, is there a concern with my MAF data range? If so, what should the range ideally be?

I would like to understand why you say fuel trim indicates a problem with the MAF.

Your feedback would be much appreciated

Thanks and regards,

Tony

Tiny
Tonyho8
Feb 24, 2012.
Tony send an email to
merlin2021@comcast. Net, I will send you a technical bulletin on the 02 and MAF system and diagnostics, your voltages are wrong for the MAF and LONG term fuel trim being 0.0 is a problem. Also short term fuel trim is constantly negative, also a problem.

Merlin2021
Feb 24, 2012.