ulmapache

Sorry if this is a repeat of an existing thread/post, searched, nothing came up.... Ok, CEL on, have code p2226 and p2228, meaning barometric pressure sensor issues. My query...is the sensor integral with the MAP sensor, or is it a seperate unit, and if so, where is it located. Vehicle is 2005 c-230 ko0mpressor. Thx....

B16RacerN2NR

It is integral with the MAF (Mass Air Flow) Sensor

Moderated - not true

ulmapache

MAF is new....no other codes present. Any idea as to what is going on?

Glyn M Ruck

Did you cancel the codes? If not it could take over 100 miles to auto cancel after fitting a new MAF & sometimes not at all.

B16RacerN2NR

I agree with Glyn...

Also, I NEVER replace a MAF without also changing the air filter(s). Did you change yours at the same time?

This doesn't happen all the time but a handful of times I have run into a problem where a new MAF won't/can't self adapt because of dirty air filters. Even only "slightly" dirty as well.

ulmapache

New air filter/fuel filter...MAF, sparkies, ignition coil assys, .... This is getting to be tiresome....and I thought my next car was going to be an E-63....might be a '40 Ford w/ a flathead....

Glyn M Ruck

Did you cancel the codes?

ulmapache

Yes, twice....

ulmapache

Am going to replace new MAF with old one and see what codes come up....back in an hr

Glyn M Ruck

Is the new MAF a genuine part? VW/Audi MAF's look identical but won't work on a Merc.

ulmapache

This one is the original, genuine part, VDO Siemens....swapped out new one for old, original one, took test drive...here's the freezeframe.

Old, original MAF/"New" MAF

ABSLT TPS 18% / 13.7%
RPM 2058 / 1072
Calc Load 15.6/11.3%
MAP 38(KPA)/29(KPA)
Coolant 96 F (not warmed up completely)/129 F
ST FTRM1 0.0%/0.0%
LT FTRM1 0.0%/0.0%
33mph
Fuel sys1 open (does this mean fuel cap open/defective?)/Open

Don't know if this is relevant, but looking at the MAF plug noticed it has 5 female recepticles, only 4 have metal contacts, MAF has 5 male pins. Does this mean anything? Here's photos...Thx

ulmapache

BTW...nice view....

ulmapache

[QUOTE=ulmapache;4935005]This one is the original, genuine part, VDO Siemens....swapped out new one for old, original one, took test drive...here's the freezeframe.

Old, original MAF/"New" MAF

ABSLT TPS 18% / 13.7%
RPM 2058 / 1072
Calc Load 15.6/11.3%
MAP 38(KPA#/29#KPA#
Coolant 96 F #not warmed up completely#/129 F
ST FTRM1 0.0%/0.0%
LT FTRM1 0.0%/0.0%
33mph
Fuel sys1 open #does this mean fuel cap open/defective?)/Open
DTC code p2228
New air/fuel filter, spark plugs, coil ignition units, no vacuum leaks


Any ideas on which sensor to go after?

Glyn M Ruck

P2228 = Barometric Pressure Circuit Low - you know this

The freeze frame tells us nothing. Just gives

Throttle position
RPM
Load
Manifold pressure, coolant temp, speed etc.

"Fuel sys1 open" means the engine is not fully warmed up & the injection system is still running "open loop" i.e with enriched mixture & ignoring O2 sensor input.

You might have to get this car onto a Star to find why the aneroid "barometric sensing" is haywire.

I do not know the M271 as well as the bigger engines. The 4 cyl models use a different injection system. I just want to check the post above that the aneroid sensor is integral with the MAF. On older models it was not & used to get full of dust & cease to operate properly. Cleaning generally fixed it.

Glyn M Ruck

Sorry the poster in post #2 above is wrong!

The aneroid/barometric pressure sensor is separate to the MAF on the M271 & thus is suspect. Clean or replace sensor 80 in the diagram. As you can see it's been updated a few times.



80 A 004 153 33 28 SENDER UNIT
ALTITUDE SENSOR
Replaced_By: A 005 153 72 28 001
80 A 005 153 72 28 PRESSURE SENSOR
ALTITUDE SENSOR
B18 001
80 A 004 153 33 28 SENDER UNIT
PRESSURE SENSOR INTAKE PIPE
B28
Replaced_By: A 005 153 72 28 001
80 A 005 153 72 28 PRESSURE SENSOR
PRESSURE SENSOR INTAKE PIPE
B28 001


Good luck

B16RacerN2NR

Just saw this... my bad. I didn't even stop to think about what engine you had... Good catch Glyn

Glyn M Ruck

No problem. We are all trying to help. I don't know if the newer sensors can be cleaned. Might now be sealed.

ulmapache

Thank you Glyn!!! This confirms what I suspected. I had the car in to a stealer for a $200 diagnostic, they found no codes, and failed to notice a disconnected vacuum line...so nothing wrong w/ car...18mpg is good....I found line after a week of beating my head against a wall.... I have one on order, should be here today, around $40. Here's something to check out, the sensor crossreferences w/ Chrysler(Mopar) MAP sensor for Crossfires. Is it possible that the Mopar sensor has the same parameters? Might come in handy if no MB parts supply available locally, and you don't want to do the internet thing. And thanks to all who have helped me in this long journey!!! Will post a big thank you when I see MPG come up to specs.....

Glyn M Ruck

It is possible. The Crossfire is built on a Benz Chassis.

ulmapache

Ok folks, fixed p2228 code, some more came up, am giving it a break for a couple of months, one code indicates a short to ground in MAP circuit..... I swear I'm going to donate this thing to a heavy weapons shoot in Bald Knob KY.....so long as I get the first shot with the biggest gun.... Again, thanks for all the help, I'll get to the bottom of this eventually.....