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I cant locate Exhaust Gas Temperature Bank 1 Sensor 1...
I unplugged these two sensors and waggled the live data on my scanner with a variable resistor.Turns out EGT Bank 1 Sensor 2 and EGT Bank 1 Sensor 3 are either side of the cat as I've shown on this picture to help others (although this guy (youtu.be/MjoIXsF2OQo) says Sensor 2 is Sensor 1...)
Appreciate if someone can show me the location of EGT Bank 1 Sensor 1. Thanks.
I've updated the image with all 4 locations in case it helps someone else out.
The tricky part was finding the connector locations in the engine bay.
Used Car Scanner app (Android Play by 0vZ) with a $5 OBDII dongle off ebay to find the codes/sensor issue and monitor live DPF regen state during drives.
You can unplug each of the EGT sensors, each will have a resistance of 220 ohms when cold. Also check the engine side connector has 5V on one of the connections.
I ordered a replacement EGT sensor on Amazon for $40. Be careful if you're ordering EGT 1, as it has a male fitting into the engine (all the others are female).
Good luck!
EGT 2 and 3 connectors are at the back of the engine bay, accessible without taking anything apart.
My problems started with EGT Bank 1 Sensor 1 faulty (open circuit, high readings etc) and DPF filter restriction (I'm not sure if the sensor fault prevents DPF regen cycles).
While I had the air filter assembly off I sprayed Liquimoly filter cleaner and purge fluid through the EGT 2 hole.
Now all the sensors are working fine, but I still have the DPF restriction which keeps the car in limp mode (restricted to 2000rpm)... Have been doing some long hard drives to try burn it off.
It's usually a good idea to attempt cleaning those sensors. Over time, buildup occurs and readings can be wonky. Good job cleaning them.
As for the DPF, it has additional sensors that restrict the car into limp mode whenever they think something may be amiss. If you have the ability to force a regen, that would be my first choice. Resetting all of the error codes may get you out of limp mode too. The ECU is way over-protective of the DPF, it could care less about your actual engine.
What's the typical use of your GLK? Do you do mostly short trips around town? How often do you get out on the open road and really heat up that exhaust? That's what cleans the DPF, getting it nice and hot. You can also try a couple bottles of the LiquiMoly DPF Protector (this stuff) into the fuel tank. It has worked for quite a few people with similar issues.
You may want to think about investing in a good scan tool that can do DPF regens, among other things. If you plan to service (or diagnose) your MBs instead of bending over at the stealership, it will save you many dollars and headaches.
Resetting all the codes, clears the engine light but it comes back after one drive cycle. I can monitor regen status and see it doing passive regens while driving (although not active regens), but my OBDII doesn't give me an indication of % restriction so I'm not sure if the restriction is changing at all.
The GLK does a daily commute, 45mins each way, all highway. Did LiquiMolys in a couple of full tanks since this started, but no change so far.
Not found any OBDII devices (under $1000) that can force regen... pls let me know if you know of a device that does. I got an iCarsoft MB V2.0 thinking that would force regen but it does not (Car Scanner app actually gives more info for DPF).
OK, if you can clear the code(s) but they come right after one drive cycle, you've got another issue that's preventing the system from doing an active regen. Can you get a list of the codes and post them?
If your scan tool can report DPF pressure sensor values pre- and post-DPF, you can figure out DPF restriction. For example, using my BlueDriver scan tool and app I can see PSIs for pre- and post-DPF pressures. It also calculates the PSI difference, which is around 0.15psi (in other words, almost nothing).
Alas, the BlueDriver cannot force regens. The iCarSoft MB scanner was reputed as one that could force regens, I think people found out it can't. Let me see what I can pull up, just know that I don't have any direct experience with other scan tools besides BlueDriver, ScanGaugeII, the Carly app (which, incidentally, I don't recommend) and OBD Fusion.
Sounds like the commute is ideal for a diesel, so the DPF is likely just fine; it's one of the myriad sensors that must be unhappy. You may want to check the DPF pressure sensor itself, there is a warranty extension just issued by MB where they will replace it if defective. If you are under 120k miles, they should cover it. I would NOT let them do anything else, including removing the DPF and other shenanigans.
Once we have more info (the codes) we can see if perhaps it's an AdBlue issue that's preventing a full active regen from occuring, thus keeping you in limp mode. I've had the AdBlue act up on me and it puts you right into limp mode, no questions asked.
Can you get a list of the codes and post them?
If your scan tool can report DPF pressure sensor values pre- and post-DPF, you can figure out DPF restriction. For example, using my BlueDriver scan tool and app I can see PSIs for pre- and post-DPF pressures. It also calculates the PSI difference, which is around 0.15psi (in other words, almost nothing).
Alas, the BlueDriver cannot force regens. The iCarSoft MB scanner was reputed as one that could force regens, I think people found out it can't. Let me see what I can pull up, just know that I don't have any direct experience with other scan tools besides BlueDriver, ScanGaugeII, the Carly app (which, incidentally, I don't recommend) and OBD Fusion.
Sounds like the commute is ideal for a diesel, so the DPF is likely just fine; it's one of the myriad sensors that must be unhappy. You may want to check the DPF pressure sensor itself, there is a warranty extension just issued by MB where they will replace it if defective. If you are under 120k miles, they should cover it. I would NOT let them do anything else, including removing the DPF and other shenanigans.
Once we have more info (the codes) we can see if perhaps it's an AdBlue issue that's preventing a full active regen from occuring, thus keeping you in limp mode. I've had the AdBlue act up on me and it puts you right into limp mode, no questions asked.
Hey, thanks for the tips.
Remaining codes are P2463 and P24AF.
Delta pressure shown in the Car Scanner app is -326KPa (-47PSI) but is responsive in the live data, so that's either garbage number from the app or pressure sensor is broken too The pressure sensor is only $20 so I'll replace that just in case.
My GLK just passed 123K miles so I missed the extended warranty by a couple months...
Ok, I’ll look up the codes and get back to you. I’m also past the warranty extension, at 122k miles, but I also took care of the problem permanently with a software solution
So, the codes: they both refer to the DPF. I think MB would call them "soot" sensors. P24C6 - Particulate Matter Sensor - Temperature Circuit P24AF - particulate matter sensor circuit performance
Trouble is, you could replace the sensor but you may have to find someone with a professional MB scan tool that can "learn" the new sensors to the car, called adaptation. It may not be enough to simply swap them out; the car's ECU may need to be told "hey, this is a brand-new sensor and i need you two to work together now."
You might have luck just removing the DPF sensors and cleaning them as well. They will be in the exhaust pipe, under the car, right before and right after the DPF itself.
If cleaning them doesn't fix it, and you need new ones, you'll need to find someone to do the adaptation for them.
So, the codes: they both refer to the DPF. I think MB would call them "soot" sensors. P24C6 - Particulate Matter Sensor - Temperature Circuit P24AF - particulate matter sensor circuit performance
Trouble is, you could replace the sensor but you may have to find someone with a professional MB scan tool that can "learn" the new sensors to the car, called adaptation. It may not be enough to simply swap them out; the car's ECU may need to be told "hey, this is a brand-new sensor and i need you two to work together now."
You might have luck just removing the DPF sensors and cleaning them as well. They will be in the exhaust pipe, under the car, right before and right after the DPF itself.
If cleaning them doesn't fix it, and you need new ones, you'll need to find someone to do the adaptation for them.
Thanks for the follow up:
I unscrewed the Particulate Matter Sensor from the exhaust and it was spotlessly clean. No soot or dirt at all.
I replaced the DPF pressure sensor with a new one, but that also shows -47psi on the scanner....? That's with the engine off and sensor plugged in. Unplugging the sensor the scanner shows +45psi, I'm guessing that +- 45psi is full swing of the sensor.
While changing the sensor I confirmed the 5V and ground in the connector and did a continuity test of the signal wire back to the ECU. All that was fine. The hoses looked in good shape with no signs of holes or splits. I used a bicycle pump to prove neither hoses were blocked.
Rev'ing the engine from idle to 2000rpm the pressure does change as shown below, but is always -47 -> -46PSI.
Cant believe -46 PSI is real or even possible for a completely blocked DPF. Having changed the sensor and checked out the wiring/hoses I'm not sure what more I can do. Any ideas?
DPF pressure while rev'ing the engine idle to 2000rpm
Just because the particulate matter sensor was clean doesn't mean much. It could have failed just the same. Maybe think about replacing it next. Although the fact that it's clean is encouraging in other ways: it shows your exhaust is coming out clean.
The DPF pressure values are interesting. If the values were real, your DPF would be pulling vacuum which is not possible. If it'd be fully restricted, the worst you'd get is no flow which would also mean you couldn't run the engine at all (think bananas in tailpipe scenario). So, those values must be coming from the ECU which is taking something else into account instead of the raw pressure reading. Especially at higher revs and more flow, you should be seeing a positive number. It's too bad your scanner doesn't give you DPF pressure difference measurements.
I'll have to tinker with mine and see if I can pull up anything remotely similar with my scan tool. It's also possible your DPF pressure sensor was fine, and what you actually needed to replace was the soot/particulate matter sensor. There was a thread around by @fmorelli who replaced his, complete with pics. Maybe that will help you.
Most important is you should be trying to force a regen of the system, whenever you replace a sensor, to see if that fixes it. Your DPF innards are fine, it's just a sensor (or two) that's not happy and ruining everyone's day. Keep up the good fight.
Turns out there was nothing wrong with the pressure sensor or the particulate matter sensor.
I did fix my DPF problems with a better scanner that forced regen. Posted details in another post here.
Thanks again for the help
Well done! Now we know of another scanner that does the job. They are worth their money if they save you a trip to the stealership where they'd fleece you otherwise.
11-10-2020, 10:39 PM
EGT Sensor Locations - Pictured
The pressure sensor is only $20 so I'll replace that just in case.
