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trouble codes p0161 p0400

 
Old 04-29-2019, 03:13 PM
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2000 ml320
trouble codes p0161 p0400

hello all i have a 2000 ml320. i recently had several codes come up for check engine they were all related to o2 sensors and egr . so i took out the egr cleaned it up made sure it wasn't stuck or anything, i was not able to get the egr tube out to clean it because of its weird bend on it i played with it for 45min before i gave up and just put it everything back together. i also changed the o2 sensors that were giving codes which were the post cat sensors(rear) with new ones. so when i turned car on drove it for a while nothing no codes, then next day woke up drove it for a bit then engine light came on again. scanned it and p161 and p0400 came up so thinking egr might be causing all the trouble not sure where to go from here guys. need a little guidance here if anyone can suggest anything or something im missing, common problem anything?? any input is appreciated thanks everyone ..
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Old 04-29-2019, 07:01 PM
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You still cant rule out the egr since you didnt get it out to clean it.
The egr comes out with some twisting and turning on unusual angles, but it does come out. I had to look at a photo of the part and twist and turn it based on its shape to get it out.
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Old 04-29-2019, 07:27 PM
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yea i was thinking that also dammit lol. yea i cleaned the main part but the tube was still in there i tried for a while to get it out while looking at pics and videos of others taking it out. i guess i can give it a shot again maybe.
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Old 04-30-2019, 05:00 AM
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Code P0161 is for a failed heater circuit at the left rear O2 sensor. M/B Part #001 540 28 17.

Your EGR Tube is probably clogged. Remove to see if it is.

https://www.benzworld.org/forums/w16...l#post12370745
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Old 05-03-2019, 07:53 AM
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Theres also the vacuum lines and solenoids.

My EGR light came on and I took the whole thing off, cleaned it, was at a loss, and finally realized it was a degraded vacuum line hidden at the back / behind there at the valve, I believe running to the throttle body. I seem to remember it was a thicker one but dont quote me on that. It had a small degraded hole underneath a bend that I couldn't see from my above inspection.

I believe the code doesnt appear right away because the ECU determines to throw it based values determined by the O2 sensor over time. (I could be wrong though) This would explain why you didnt see it right away.

The check engine light will also eventually blink to warn you of potential damage to the catalyst.

I believe fixing it will also improve your idle and fuel trims.

You can check the vacuum canisters rubber interiors with a hand squeeze suction device. You can try just sucking on them but it's not always conclusive, it requires a bit of suction and tastes bad...but yeah if it just flows air or doesnt hold a suction on it for awhile it's bad. Make sure it actuates its thing too and isnt seized. The solenoids can be checked with a quick jolt of 12v (try not to hit them with huge amps lol)

I also realized the other vacuum lines at the front to the two mushroom looking things were degraded and about to or were leaking. Same with those running to the intake manifold runner length change over black plastic mushroom thing and the black electric solenoid at the front. They can look fine from the top but the bottoms just break down.

I seem to remember some of these hoses being different OD/ID then the others so take them in with you when you go to the parts store... and look for their "extra pieces" box of their vacuum hoses for cheap deals!

Oddly enough I had the same problem with my O2 sensor, rear on the drivers side. Turns on the connection was bad. Once I cleaned it, it worked for awhile but then the o2 sensor gave out... now its seized in the damn pipe and corroded and just turns so i dont know what I'm going to do.

Do post back and let us know if you get er' fixed!

Goodluck!

Last edited by SpenserM; 05-03-2019 at 08:05 AM.
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Old 05-05-2019, 07:43 PM
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So I tried again and got the egr tube out, found out you gotta pull that breather tube out to get the right swing angle to remove it. So I cleaned the tube thoroughly and replace one of the tubes on the valve that were degraded with matching one from part store put everything back up. Then I pulled the plug on the o2 sensor giving trouble cleaned the connector pins with rubbing alcohol and cutips, and connected it back. Cleared codes and drove for a bit and then bam engine light came back on. Codes still the same p0400 and p0161. I'm stumped not sure what to do from here thinking new egr valve or solenoid , and new 02 sensor. What do u guys think? with the 02 sensors are there any fuses or a way to check the connection to 02sensor without having to go under the car?
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Old 05-05-2019, 08:14 PM
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Originally Posted by shaman369 View Post
So I tried again and got the egr tube out, found out you gotta pull that breather tube out to get the right swing angle to remove it. So I cleaned the tube thoroughly and replace one of the tubes on the valve that were degraded with matching one from part store put everything back up. Then I pulled the plug on the o2 sensor giving trouble cleaned the connector pins with rubbing alcohol and cutips, and connected it back. Cleared codes and drove for a bit and then bam engine light came back on. Codes still the same p0400 and p0161. I'm stumped not sure what to do from here thinking new egr valve or solenoid , and new 02 sensor. What do u guys think? with the 02 sensors are there any fuses or a way to check the connection to 02sensor without having to go under the car?
Looks like you'll need to replace the sensor as Maj. Dundee stated - #001 540 28 17
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Old 05-05-2019, 08:37 PM
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About the egr I'm thinking the valve is broken but I was able to move it with finger and screwdriver up and down and got some lubricant in there and heard the air pumping when I was pushing on inner valve or a hose is broken somewhere I'm not seeing or maybe the right or left egr air pump check/ shut of valves possibly I dunno. Any ideas??
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Old 05-05-2019, 09:05 PM
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Try reversing sensors with the known working sensor with the bank 2 position 2 sensor and see if it goes away. It's just the heater circuit so all that's for is getting the sensor up to temperature on cold starts so the readings are 100% correct to minimize emissions. It's not a critical thing but not having the check light would be nice.

For the egr

(Look at diagram of egr and connections)

Did you check the vacuum line running to a...that it is both without holes and plugged in on the other side? (That's the one I had problems with and didnt see right away) and did you check that the y31 "vacuum transducer"/solenoid works?
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Old 05-05-2019, 09:06 PM
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Originally Posted by shaman369 View Post
About the egr I'm thinking the valve is broken but I was able to move it with finger and screwdriver up and down and got some lubricant in there and heard the air pumping when I was pushing on inner valve or a hose is broken somewhere I'm not seeing or maybe the right or left egr air pump check/ shut of valves possibly I dunno. Any ideas??
How do you know the egr is broken? - do you mean the valve body?
Did you check the vacuum lines you may have disturbed / removed while pulling out the egr tube, especially the larger vacuum line just under the egr tube that connects at the back of the engine. It may be loose or cracked?
For the age of this suv, vacuum lines get brittle and do crack.

edit - goto 815min mark - possibly this? but I think you would have seen it with vacuum hose not connected.


Last edited by khomer2; 05-05-2019 at 09:11 PM.
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Old 05-26-2019, 09:40 PM
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OK guys so changed egr valve and change over sensor, replaced some old tubing and code went away with clearing. I also changed the rear passenger side 02 sensor and cleared code took it for a spin and engine light came on this time the code was p161 and pending code of p700 and 720 but the 7 codesnippets always come up and eventually go away but I'm still getting the p161 so I'm thinking it has something to do with the wiring when I pulled the old sensor out it was stuck and the tube with the sensor connecter tube pulled out a couple of inches but I pushed it back in and changed the sensor any way and cleared the code but I'm still getting this p161 code after changing the sensor so I'm stumped. I think it has something to do with the wiring I don't know where the sensor wires connect to to follow it to see if there's a break or oil in it some where I was leaking oil for a while until gasket change. Any ideas on what to do next guys I appreciate the help so far.
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Old 05-26-2019, 10:01 PM
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Originally Posted by shaman369 View Post
OK guys so changed egr valve and change over sensor, replaced some old tubing and code went away with clearing. I also changed the rear passenger side 02 sensor and cleared code took it for a spin and engine light came on this time the code was p161 and pending code of p700 and 720 but the 7 codesnippets always come up and eventually go away but I'm still getting the p161 so I'm thinking it has something to do with the wiring when I pulled the old sensor out it was stuck and the tube with the sensor connecter tube pulled out a couple of inches but I pushed it back in and changed the sensor any way and cleared the code but I'm still getting this p161 code after changing the sensor so I'm stumped. I think it has something to do with the wiring I don't know where the sensor wires connect to to follow it to see if there's a break or oil in it some where I was leaking oil for a while until gasket change. Any ideas on what to do next guys I appreciate the help so far.
Dude isn't bank two sensor two the driver side? Is your truck a Left hand drive or right hand drive...because north American left hand drive is driver side for bank 2. Sensor 2 being the down stream post cat sensor.

Also I know this isn't really any consolation but the P0161 code is just for the heater circuit. The heater circuit is only used to heat up the sensor when the engine is cold. As far as my understanding goes this was only really implemented so that the readings were as accurate as possible even when the engine is cold in order to reduce emissions.

The sensor still functions, albeit less accurately when cold. Also to my understanding the downstream O2 sensors only exist to make sure the catalyst is working correctly. The engine computer does not use the readings to tune or adjust the engine. Basically the whole thing is an emissions verification system.

Still I get it, check engine lights are not fun!
You can check the voltage with a multi meter if you look up the pins for 02 sensor...the heater circuit should be putting out +12v soon after you start the truck. I don't know where it gets that 12 volts from whether it has a relay, fuse, module, or is just from the ecu. You should be able to search that function. I believe the ecu is just checking to make sure the circuit isnt open however I dunno if it supplies the voltage. I suppose some Google kung fu could find out.

But yeah like I said I think you got the wrong sensor location. Maybe try reversing the sensors and see if the code changes?

Also I'm glad you fixed your EGR code, I hope my advice helped!

Oh btw if you know or happen across how to find out what puts out the voltage to my driver side heated seats in a 99 that would help me. The lights come on when I hit the switch and I know the relays under the seat work and the seat heaters themselves...I'm just not getting the relay signal or maybe the 12 volt for the seat (cant recall which one or both)

Thanks and good look!
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Old 05-26-2019, 10:30 PM
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Also your potential p0700 and p0720 codes for the transmission might mean a lot or nothing. However even the most likely worst case scenarios shouldn't be expensive and won't even require removal of the transmission.

In my experience when I checked my codes I got similar pendings like 50 000km ago and haven't had any problems.

The first thing to do is get your fluid level checked by either taking it to someone who has a dipstick or ordering it online.

After that there's an electrical connector on the bottom side of the transmission that goes to the Transmission Control Unit (tcu). There's sort of a defect or common problem with the adapter plug that goes into the transmission where it begins to leak transmission fluid...the fluid can then wick up the wires and get into the TCU and short it out. Luckily the plug is inexpensive at only 20-30$ and easy to replace. So yeah check the adapter plug and the wires coming out of it, they're usually under the heat shielding wrapped around them, see if its leaking or wires are wet. I would almost just replace it as a precautionary / preventive maintenance thing.

There's also a common problem with the "conductor plate" inside the the transmission. These again are inexpensive and are rather easy to replace. Theres kits on Amazon with the plate, speed sensor, that adapter plug, transmission filter and gasket for like $100!

Sometimes but rarely the valve body or one of electric valve solenoid things break and again those are easy and not much to replace.

If the transmission does get worse, it will usually pop you into a "limp (home) mode" putting you in second gear and allowing you to limp it home. If this happens try turning the truck off and waiting a bit and it might go away for a bit.

There's good articles about all this on Mercedes medic. But yeah while you're under there messing with the 02 sensor check that wiring coming out of the adapter plug (it's probably coated in oil on the outside heat shielding already if you've had any sort of leak in the past...clean it all up, even under the shielding). If the plug appears to be leaking replace it immediately. And check that fluid level.

Good luck.
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Old 05-26-2019, 10:42 PM
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Oh also if you think you damaged the wiring or plug to the 02 sensor, I'm fairly certain the wires go into the cabin and run under the carpets to the firewall then to the ECU under the hood. In some of the older MB like the w124 and w140, I believe there was a connector under the carpet somewhere that you could unplug, so that the wires leading under the car were like an extension (I believe this was so the wires could be fed up from the bottom through a small grommet and they could use a small non water tight connector to pass up through that small grommet). But don't quote me on that! Lol.

You should be able to see at the back of the connector underneath if you pulled any of the wires out of the pins or if you pulled the pins out.
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Old 05-26-2019, 11:29 PM
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Man I love you guys and this forum... I never thought about the left right thing I most certainly will be checking that out tommorow I still have the old sensor so I'm going to swap it tommorow. I would of never thought that the driver side is the bank 2 sensor 2 I was looking at diagrams but it said passenger side so I changed it but I'm gonna change the drivers side tommorow and get back. I'll also try to follow the wire from under the carpet to check if anything a miss.
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Old 05-26-2019, 11:33 PM
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My car is a left hand drive and I've changed the passenger side rear sensor so I'll change the driver side tommorow
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Old 05-26-2019, 11:54 PM
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Originally Posted by shaman369 View Post
My car is a left hand drive and I've changed the passenger side rear sensor so I'll change the driver side tommorow
Don't forget to check the transmission adapter plug while you're under there for transmission fluid wetness on the wires!!!!...save yourself the money on a TCU replacement or repair. (Google image search for the "w163 transmission adapter plug" to get a good idea of where you need to look at...oh **** that just refreshed my memory, there's like a little sheet metal plate that may be covering part of it, you may need to remove the plate with a 10m bolt or something to see it)

Oh also in my experience if the transmission is low on fluid the first sign will be it will shift funny or almost like hold a gear at slow speeds especially when cold. The truck will also run at higher rpms it seems on the highway. This is just a theory but perhaps you may get a pending code when the fluid is cold and hasn't expanded however it heats up fast enough so that the parameters the TCU needs to see a number of times or for a certain length of time to throw the code dont occur...hence the pending code.

Anyways dont forget the check back even if you fix it all!

Good luck, enjoy the rest of your weekend, drive safe, and use jackstands and wheel chocks and safety glasses when underneath :P
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Old 05-27-2019, 02:26 PM
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Thanks spense I'm about to go under now I'll let you know how it goes.
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Old 05-28-2019, 01:20 AM
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Alright guys I think I did it. Changed the 02 sensor on drivers side cleared the codes and drove it around for a while and nothing came up. I think I'm in the clear. thank guys I'll check back in later...
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Old 05-31-2019, 11:28 PM
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OK guys I'm clear for engine light. But I'm now working on trying to complete a drive cycle so I can get ready for inspection emission test (nj). CAT , EVAP, 2AIR is coming up not ready. I have been driving it around for about 5 days now and making some unecessary highway drives but still not reading ready. Im gonna try to complete the odb readiness procedure from on another thread here I found . But if any ones knows any tricks or ways to get around the crazy driving this thing takes to complete a cycle, I'm going to have to find a long open road to do this procedure, unless one of you geniuses know a thing or two to fast track it??
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Old 05-31-2019, 11:46 PM
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FYI drive cycle : generic OBDII drive cycle
Begin with a cold start (coolant temperature below 122 degrees F and the coolant and air temperature sensors within 11 degrees of one another). This condition can be achieved by allowing the vehicle to sit overnight, and then by beginning the drive cycle the next day. Most drive cycles will be difficult to follow exactly under normal driving conditions, so the driver should exercise caution, road safety, and courtesy to others.
* Start the engine. Idle the engine in drive for two and a half minutes with the A/C and rear defroster on.
* Turn the A/C and rear defrost off, and accelerate to 55 mph at half throttle.
* Hold at a steady speed of 55 mph for three minutes.
* Decelerate (coast down) to 20 mph without braking or depressing the clutch.
* Accelerate back to 55 to 60 mph at throttle.
* Hold at a steady speed of 55 to 60 mph for five minutes.
* Decelerate (coast down) to a stop without braking.
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