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It was cold again this morning (car stays outside) at 18*F. I experienced the same Limp mode as before. I kept driving it and after about 20 minutes I stopped and shut the engine off/on three times within about a minute. Made no difference.
I then drove another 10 minutes and turned the engine off long enough to go into Dunkin Donuts to get a coffee and back out. I started the engine back up and checked for codes (through OBDII with my little scanner) and got a "pending" code of P1402. I did NOT clear it. I then started driving and everything was back to normal.
P1402 (according to Google, anyways) comes back as an EGR issue (most likely this was the code I reference above, but did not remember it correctly). However, this is not through STAR and I also know that experience often trumps what a code/scanner may say.
But...
-- Could the cold weather be affecting the EGR and once the engine warms up everything returns to normal? Can the EGR be cleaned?
-- Or, is the most likely culprit still the DPF sensor?
Over the past 3 winters, our 320 CDI would go into limp mode 3 or so times every winter at times when temperatures dropped to below -15 deg.C. With every new 'round' of this happening the CEL does not come on at first, but it does by the 2nd day and I would get code P1402.
I recently replaced the Pressure Differential Sensor and I'm pretty sure my trouble is over now!
Over the past 3 years, our 320 CDI would go into limp mode 3 or so times every winter at times when temperatures dropped to below -15 deg.C. With every new 'round' of this happening the CEL does not come on at first, but it does by the 2nd day and I would get code P1402.
I recently replaced the Pressure Differential Sensor and I'm pretty sure my trouble is over now!
Thank you for that information. I never even thought to check the ML forum. Thanks for the thread link, too - that was interesting. It definitely seems like "cold" is the trigger. Water/ice would definitely explain it - I suppose electrical connections getting cold and "shrinking" ever so slightly might also explain it.
Whatever the cause, it certainly seems like it's the sensor. I checked mine last night and it had the old part number. Everything came apart nicely (put it right back on for the time being) - I'll order a sensor.
It says, in the product description, that it relates to the A 642 905 01 00 MB number. I also found that Bosch part on FCP Euro's website, but they were already closed when I called. I'll try calling them tomorrow to try and verify. If so, unless anyone knows that the Bosch part is junk, I'll probably give that one a try. Maybe Bosch is the manufacturer for MB? Worst case, it's an easy part to change.
Awesome! Thank you! It looks like the new part you have has a different Bosch part number than the one I found. Maybe the one you have is an even newer version as the number is higher. I'll check around.
Correct. I did that because I know this issue was documented already on MBWorld forum before
No worries. It's always good to learn a new way to search. I did search (through the site's function) and Google quite a bit. But I was restricting my searches to "GL", although I did try some "0M642" searches, too. For whatever reason, I just wasn't finding what I needed. I was getting bits and pieces, but not enough to make sense (to me, anyways).
Every place I contacted didn't have the non-MB labelled unit. It was always on backorder. FCPEuro contacted Bosch and still couldn't get a bead on when it would be available or why it wasn't currently. So I just ordered the MB-branded sensor from FCP. I don't mind spending money to fix things, but I hated to spend the extra $35 for a Mercedes symbol screen printed on the part Besides, I didn't feel like spending any more time trying to find the Bosch unit just to save a couple bucks, either. I'll pop the new one in when I get it and cut the old one apart.
Sounds good. Eager to hear back whether the new replacement does the trick in your vehicle.
My old unit had a small puddle of water inside when it was opened up and I wondered if the unit had first been warmed up gently with a hair dryer before opening it, whether the moisture could have been driven off and what difference that would have made to its functioning. I would still have replaced it with a new one though, but as an interim measure perhaps ...? The water obviously didn't simply drain out of the old unit through the 2 plastic tubes despite the tubes pointing downwards in the installed position. Also I used a hack saw to cut open the unit, but this tool destroyed much of the finer details inside of the unit.
Well, my attempt at hacking it open wasn't much better. I used a dremel cutoff wheel and then removed that white, rubbery stuff you pointed out, along with the circuit board. I removed the burring with a blade. The only thing this really shows any better is the two different "chambers" that are, essentially, on either side of the white, rubbery stuff. Obviously, creating the pressure "differential" part. The funny shaped chamber in the center (left side) is connected directly to the lower tube (although in the picture it looks like it is not) via a "tunnel" through the plastic wall between the chamber and the tube. The white, rubbery stuff/switch separates the funny-shaped chamber from the upper, right-angle-shaped chamber.
And, mine had some water in it, too. The part had a date stamp of 2008 on it, so I suppose it's not really all THAT bad of a lifespan. Thinking more of this water thing, I'm having a hard time imagining that even a new one wouldn't accumulate some water. I mean, all exhaust systems accumulate water from condensation, etc. You see it dripping out of the tailpipes all the time. BUT, it is strange/coincidental that my problem ONLY happened when it was quite cold out.
Because the water froze and changed the volume of the chambers? Just a random thought...
I was going back and forth on this idea. I can certainly understand how it could affect things, but I don't understand how/why it wouldn't also affect a new unit? That's the one that has me scratching my head. Unless maybe there was some exhaust particles the clogged things up and didn't allow the water to drain back out. But then, the water would have still stayed in there - regardless of temperature, right? Just another random thought!
DennisGo1, thank you for your photo - you did a much better job of opening up the unit than I did!
I'm also not sure why a new unit wouldn't very quickly gather water and then malfunction. Perhaps it takes a certain number of hot cold cycles for the small chambers inside to accumulate the required amount of condensate to cause a malfunction under freezing conditions.
Self explanatory detail in the unit may also have been destroyed when opening the unit.
It would be nice if someone at Bosch commented on this!
Ok sorry to drag up an old thread but something weird happened with our GL x164 2008 420 v8 diesel. Hope you guys are still on here.
Long story short cars only done short runs due to Covid recently but hasn’t missed a beat. We are in the UK its June and on the hottest day of the year so far this happened (28.5c). We were driving from Newcastle to Blackpool about 140 miles and about 50 miles in this happened.
My wife was driving and overtook a long line of lorries. When we reached the next big hill we experienced what was either limp mode with no CEL or other faults on the dash. We pulled over and swapped seats an I drove it to try and troubleshoot the issue. No dash errors or lights, no issues with engine temps, auto box was shifting fine but down on power. Could get her up to 60 an carry the speed but throttle was topping out around 2100-2400 revs. If I tried to blip the throttle either gradually or sharply it would respond by about 100revs and drop back down, even tried gradually increasing to full throttle and it stayed at 2200 revs.
So drove/limped on to Mercedes Carlisle who were helpful on the phone, but the workshop manager wasn’t interested and said it would be a couple of hours atleast before someone could look at it.
Before I went in I checked under the bonnet and under the car no leaks or pipes dislodgeed. Turned the car off and back on and it would rev fine all the way to redline. I was weighing up all the risks and thought based on what I’ve seen and fact we have AA recovery I thought restart the journey. So we drove on to Blackpool and returned the same day (220 miles) no further issues.
Got home checked for codes nothing. Until I read this post I was thinking throttle pedal issue due to no lights on the dash and the key reset worked (or IT fix as I call it on and off worked).
Just wondered if you guys experienced it again post sensor change?
Ok where roughly is the sensor and I’ll see if I can locate mine? Might be slightly different on the v8.
This particular sensor is only found on diesel powered vehicles (unless the same sensor is used in other applications as well) for their emissions controls.
My vehicle has never had the same problem since replacing the sensor.
Last edited by 2008 ML 320 CDI; 06-28-2020 at 11:55 AM.
This particular sensor is only found on diesel powered vehicles (unless the same sensor is used in other applications as well) for their emissions controls.
My vehicle has never had the same problem since replacing the sensor.
Awesome, our GL420 is the V8 OM629 diesel, weirdly it was also used in planes!
Ok where roughly is the sensor and I’ll see if I can locate mine? Might be slightly different on the v8.
I can't speak for the V8 and what emissions requirements there are over there (we never had the V8 option here in the States). But on the assumption that you have a DPF and that you have the sensors - it's right there by the DPF underneath the vehicle. Easy access (on mine, anyways).
Ok where roughly is the sensor and I’ll see if I can locate mine? Might be slightly different on the v8.
On the 2008 V6 the sensor is located on the underside of the vehicle, in the prop shaft tunnel and in the vicinity of the front end of the rear prop shaft. I believe in some other V6 models it's located in the engine bay against the fire wall in the vicinity of the turbo.
01-08-2017, 01:10 PM
Besides, I didn't feel like spending any more time trying to find the Bosch unit just to save a couple bucks, either. I'll pop the new one in when I get it and cut the old one apart.
