Hi,
Maybe I can recap.
Code 400. What is this?
OBD codes (as used on M112 engine which i assume is the engine fitted to this car) follow the format P0179 etc.
Are we referring to P0400 = EGR Flow.

Would like to help but need to confirm Problem Description..

Sounds as though problem has been made more complex by changing parts which didn't need changing an d maybe not to the correct spec.
Why did you have to modify the wiring on the O2 sensors? I believe the O2 sensors don't actually have heaters or are we talking california spec?

EGR fault indicates excess NOx which is a combustion temp related issue. Exhaust gas makes the combustion less efficient and reduces temperature of combustion.
Is the EGR valve operating? Have you checked electrical and mechanical functioning?

Stuart.

 

Hello Blue, Thanks again for theinformative reply.
Air filter is new and clean. When I change, I take off whole canister for a good cleanning and drying.
I have three new coil packs, one of them is on cylinder two the one that seems to have a problem now.
I Very carefully in the beginning of all this inspected the two vacuum actuators for a bad hose, connector, etc. No I did not run a leak test on them since all conectors, tubing seem fine. Guess I should go there next.
Wondering if the "aftermaket " Bosch 02 sensors could play a role?

Also, could it be abad fuel injector? Never messed with thoes boys before and would be kinda clueless. My guess they would be under pressure. Have not noticed any wet/gas around any of them.
Could a bad injector cause whats happening? Any and allhelp would be appreciated. One thing definate, car is running to rich. - Jack

 

Hello Snanceki, Thank You for your time reviewing my situation.
Car is 1998 E-320 135,000 miles.
When PO400 code was pulled I change the EGR valve ( Pierburg )
OEM exzact spec.Figured the valve was original and needed a swap
out. Car has not since the long run I did come on again. ( and has not
since.

I guess I really screwed up by replacing all four 02 sensors, they where
all original. I purchased a Bosch universal sensor that needed to be
spliced to the original 4 ( four ) wire connector which I did with great
caution. Now all four sensors read codes pretainning to a heater
malfunction. Front sensors Bank 1 sensor 1, Bank two sensor two
show signs of light carbon.
No doubt about it, engine is runnin to rich. Your help is and has
been appreciated. - Jack

 

Hi,

What has lead you to conclude that the car is DEFINITELY running RICH? Soot on the plug? This may not be due to a rich mixture. Are all plugs "sooty" or just one?

So what is your problem now that you have changed the EGR. Has the P0400 code gone? Sounds as though it has. build up of carbon in the valve is the usual problem.

Are you able to refit the original O2 sensors? If you are now registering new (O2 sensor) problems the O2 sensors must be incorrectly wired or the wrong spec.

If you have no codes i don't understand what you are trying to correct. Why new coils?

Yes injectors can go out of spec but unless you have reason to suspect they are faulty changing them is needless expense. There duration of "fire" (i.e. mixture strength) is controlled electronically by the duration of signal pulse from the ECU which checks emmission level (mixture) through the O2 sensor FEEDBACK.

Maybe you can recap any remainingf problem that you have.

Stuart.

 

snanceki, Thanks for your help. Replaced two coils last year code came up. Had no problem since.
Problem now is rerplaced O2 sensors. When the code came up for PO135 and the rest of the sensors pending I changed them all out. Car has 135,000 miles and had original sensors. I 'am taken the car in August for a trip and did not want the pending sensor codes to come up while out of town - that was my logic. I replaced with a 4 wire Bosch sensor that wires corresponded with original harness/connector. Black-black, grey-grey, white-white, white-white.
Reset CEL check electronics does not come on immediately- sometimes on a short run not at all. After a 25 mile run today it came on, read code immediately, it was for all four sensors- heater malfunction. I realize that plugs do have a certain amount of carbon but cylinder 2 plugs are burning differently than the other cylinders. No injector code has come up. Respectfully, Jack-

 

Hi,

O2 sensors don't last forever. Over time they loose their responsiveness so they MAY be getting/got to the end of their life. Mine are fine at 120k and the tips have a light grey colour.

Best way to check responsiveness is to connect an APPROPRIATEscanner to the OBD port and observe the waveform/voltage.

O2 sensors have more things that make them different than the colour of the wires. OK Bosch are LIKELY (but I'm not sure) the OE manufacturer but even so they make many types.The heater circuit will be checkedat startup and this is the time I would expect the CEL to signal a problem. i.e. even before you start the motor. Can't think why you get an O2 sensor problem at the end/during a long run. The heaters don't operate under these conditions.

I suggest a bit of research to determine that the O2 sensors you have fitted are identical with the exception of the plug. The Bosch web site should be able to help so long as you have the old and new numbers etc. otherwise you need to get back to where you started.

PENDING codes mean that threshold conditions have been breached but only temporarily. i.e. maybe during a heavy acceleration which may notbe common in your normal driving therefore the conditions have not been repeated, and therefore the code status has not changed to STORED and as a consequence the CEL has not been illuminated due to this code. A transient problem was however experienced. Only STORED code can cause the CEL to illuminate and many require the fault to have been experienced several times in order to reduce the possiblity of a false positive result. Some cause the light to illuminate IMMEDIATELY however.

If the sensors are appropriate then I suggest something else is triggering an O2 code. Could be our old favorite the MAf Mass Airflow Meter but this usually gives a P0173. The MAF causes the engine to run RICH and can be verified by obtaining the LTFT (Long Term Fuel Trim) results from the OBD computer. Once the LTFT reaches 30+ the system runs out of range (it can't weaken the mixture enough as measured by the O2 sensors) and triggers the P0173 code.

You didn't state why you are so sure your engine is running rich. I suggest its because of your plug 2 colour. If only one plug is the wrong colour then the fault has to be due to a single cylinder fault (leaky injector/valve guide sealetc). Fuel mixture is partly common to all cylinders (MAF) with feedback and fine tune specific to a single bank (O2 sensors) on a two bank V engine. Individual injectors CAN cause a single cylinder problem (eg dirt ingress causing leak at injector tip) but unusual.

Are you using oil?

What results did you get from the yearly emmission certification test give? If its rich it will fail!!

Hope this helps.

Stuart.

 

Hello and thank you everyone for your help.
A few of the original problems have been solved.
1) NEVER NEVER EVER use "Bosch universal "O2 sensors in your Mercedes, expecially if you buy them off E-bay. You know the type, need to be connected/wired to the original connector. Lesson learned! Purchased OEM with connectors-problem solved! Bank 1 sensor 1 is a specific application.

2) You can replace the EGR valve, but the tube running inside the engine is critical that it be free of carbon,debris or the PO400 EGR flow malfunction code will continue. A mechanic at a local dealer /MB explained to me how to use a carb cleaner and air pressure to really clean the tube ( no need to buy a new one! ). Problem solved.
Still have a problem with occasional missfire on cylinder 2. New coil, wire, plug still carbon fouled after a week or so. Replaced camshaft position sensor ( 10 minute job ) car seems to start better without the smell of unburnt gas. Let you know more about this with more time. If problem continues the only place to look would be the injector/seal ( what the heck the car is 10 YO ) For now things are looking better, again thanks, an any ideas etc is always appreciated. Will keep you posted , and will try to download a picture of the vehicle.- Jack

 

Codes in the range of p0400 are all related to egr and emmisions ,p011-- p013-- and more, Are o2 issues,If you have more then one code going i.e. all for are showing a failure code,suspect the splice in the wires.check all your splices,clear the codes and see what happens.When you replaced all the sensors did you apply anti seize on the threads?and did you apply a little to much?that can kill an O2 quicker than I can skin a cat.
read all the codes again after you erase them and check the wires,post them and let's take a look.If you cant locate it ,find a diagnostic scan tool,and get the values,like someone said above.
ohlord
"GOT CODES?"
okay read you have it solved,save for the misfire.check for injector switching by listening to that injector with a stethescope her it buzzing and clicking?much easier to track down a miss with a scanner.

 

Hello I just purchase this car and i had a code po400 how does that cost to get fixed? Also do that have anything to do with my fuel gauge working on and off. When i turn the car off sometimes it is reading on empty and i just put gas in the car?? Need help on what possible this could be and how much it will cost to get fixed thanks Erica

 

Need to define car type, mileage, service history etc.
P0400 has nothing to do with O2 sensors. Where did this come from?
P0400 is EGR valve issue. Common problem at high mileage. Get gummed up.

Stuart