Repeated EGT (Exhaust Gas Temp) Sensor Failure in a Diesel. Any Ideas?

tunzafun001 on 02/07/2023 - 17:51

So my parents merc diesel threw an egt sensor failure code. Had to butcher it to remove it. Cant tell you why it failed.

Cant get replacements here, so bought a replacement from the UK. Lasted a few months, then failed.

To save a few bucks, bought one for $60 from Ali Express. Died on first drive.

The UK version still works initially, gives a reading, then goes open circuit once warmed up. So appears it has a crack somewhere.

The Ali Express version is open circuit straight up.

Any ideas what could cause 3 failures?

The wiring is well supported (so not flapping about).

Also, any ideas where to source one locally? This has a 13.6mm thread.

Cheers

Automotive

Comments

  • magic8ballgag on 02/07/2023 - 18:17
    +2

    Take it to a specialist, or at least post the model/year/engine etc.

    • tunzafun001 on 02/07/2023 - 18:34

      It's a 2012 GL 350 - V6 turbo diesel.

      Not an overly complicated job, but now suss with 3 dead. If it was running hot/ lean, you would think it would throw other fault codes. It does say sensor is short to positive as part of the fault code (but that might just mean it is open circuit).

      Might just be plain bad luck.

      As for Specialist… Dont think they exist any more. You need to be the specialist.

      • brendanm on 02/07/2023 - 18:55
        +1

        Test continuity between each of the pins and the sensor body. What brand was the one from the UK. The Ali one failed because it's a piece of crap.

        • tunzafun001 on 02/07/2023 - 19:06

          No continuity to the sensor body.

          The brand is a German brand 'SKV'.

          • brendanm on 02/07/2023 - 19:09

            @tunzafun001: For both pins? What about for the Ali sensor? Never heard of skv.

            • tunzafun001 on 02/07/2023 - 19:39

              @brendanm: The ali sensor is just open circuit everywhere.
              It did work on initial idle. Monitored it going up to 210C and working. Then car went into limp mode. Checked sensor..open circuit.

              Still have the old SKV, which shows varying resistance with a heat gun. But put it down, had lunch, come back and it was open circuit (heat soaked in and expanded a crack maybe). Once cooled, its showing a resistance again.

              Cant find an egt in Oz, so the SKV

              https://www.auto-doc.ie/esen-skv/14254688

              • brendanm on 02/07/2023 - 22:46

                @tunzafun001: I found a few online locally, though they are also brands I wouldn't trust personally, also not sure which egt sensor you are needing, as they have a few. Merc would probably have some in stock, or you can get genuine Delphi out of the states for about $90US. Can't trust non-oem stuff for sensors really.

                • tunzafun001 on 03/07/2023 - 10:25

                  @brendanm: Cheers. Local suppliers (like Goss) say they have them online, but its not the right one. Dont know the good brands, so appreciate the heads up on the Delphi.
                  P.S. From Merc direct..$350!

      • magic8ballgag on 02/07/2023 - 18:57
        +1

        As for Specialist… Dont think they exist any more.

        They definitely do, but I understand your desire to repair it yourself.

        I would recommend sussing out any of the Facebook groups for the same car, you'll be able to search the group and most likely come across others that have experienced this exact same issue.

        • Dslrfirst on 03/07/2023 - 09:56

          "this exact same issue"? To be sure, to be sure.

      • payless69 on 03/07/2023 - 07:24
        -1

        Likely clogged injectors,
        too much to deal with cheap sensors.
        Did you reset the engine computer after sensor replacement?
        Mercs usually store endless codes but access is usually difficult to them. Price you pay with overengineered stuff.

        • tunzafun001 on 03/07/2023 - 10:28
          +1

          Yeah, cheers. Reset each time.
          It could be an injector type issue causing an overheat situation (frying the egts which sit just behind the turbo).

  • Dealseeker21 on 02/07/2023 - 19:08
    +6

    12 year old Mercedes - Time to be made into Coke cans

    • tunzafun001 on 02/07/2023 - 19:44

      Probs..horrible cars to work on. Only done 90k km though. Which is nothing for a diesel.

      • racer1234 on 02/07/2023 - 21:44
        +3

        Horrible use scenario for a diesel though. They need to be driven to keep carbon buildup down. Short trips kill them. Get rid of it as fast as you can.

        • tunzafun001 on 02/07/2023 - 21:53

          I hear you, but they live near an expressway, most driving are 16km trips in a 100km zone near home, or drive around Australia.. Its the right 'car', but since the motor is made in the states…its SUCKS. No thought on being able to work on it / put together rubbish.

    • Leadfoot6 on 03/07/2023 - 11:09

      That is why I like to keep my Australian made 2004 Mitsubishi Magna TL All Wheel Drive in tip top shape.
      It still drives perfectly, and has every possible feature that I need.
      I used to sell Mercs in the late 1990s.
      By then, it was obvious that the quality was dropping.

  • 2jzzzz on 02/07/2023 - 20:28
    +4

    I got all my merc parts from USA funnily enough, store was FCPEURO

    • tunzafun001 on 02/07/2023 - 21:50

      Cheers. Unfortunately they dont sell EGT sensors.

        • 2jzzzz on 03/07/2023 - 09:38

          They seem like good prices for OEM if they suit your car

        • tunzafun001 on 03/07/2023 - 10:32

          Thanks for trying, but that is the wrong type. Their model is the 195kw version (naturally a rare model on the transition to the newer 2015 motor).
          I should have said when I put their car in it says it doesnt fit, and the picture is wrong as well. Theirs threads in, not a nut type.

          • Protractor on 03/07/2023 - 10:53

            @tunzafun001: Take the VIN to Partsouq website and go from there. Also try Rockauto.
            ( If you buy drive elitist brands, you have to expect to spend $$$ on a fix, or buy accordingly)

          • brendanm on 03/07/2023 - 12:36

            @tunzafun001: There are ones there that screw in, there are three different egt sensors in various parts of the exhaust. Easier if you specify which engine designation, and which sensor it is you have a problem with.

  • chillybags on 02/07/2023 - 20:39
    +2

    I had repeated EGT sensor issues on my 2016 qashqai. Like im talking 8-10 warnings over a 2 year period. Replaced the sensor 3 times, even replaced the turbo. They couldn't fix it. Under ACL I asked for a refund on the vehicle (multiple repeated minor failures that could not be fixed in a reasonable time constitute a major failure). Nissan said no and kept trying to fix it - also wouldn't put it on paper that the vehicle was safe to drive so had a hire car pair for by them for a significant period as well.

    Once I had a court date booked with NSW tribunal their lawyers got in touch pretty quickly and settled it before court. Paid $27k initially for vehicle and got $19.5k back after 3 years and 90k km on the clock.

    • payless69 on 03/07/2023 - 07:26

      Most Nissan service managers eventually become uber drivers….

      • Protractor on 03/07/2023 - 17:43

        Most Nissan service managers know less about cars than uber passengers. You could apply the same formula to most of the brands sold here.

    • magic8ballgag on 03/07/2023 - 12:27

      So you were compensated and were also allowed to keep the car?

      • chillybags on 03/07/2023 - 16:08

        No once I got the “refund” the car went back to Nissan

  • pharkurnell on 02/07/2023 - 22:16
    +1

    tried https://partsouq.com/

  • Sinnerator on 03/07/2023 - 07:38

    could also be the ecu interpreting the data from the sensor

    • tunzafun001 on 03/07/2023 - 10:33

      The sensors ars definitely dead (measure Open circuit).

  • bhubb18 on 03/07/2023 - 08:11
    +1

    Try get a genuine sensor? Cheap sensors are often garbage, particularly for this use case (Very high temperature, obviously).

    • tunzafun001 on 03/07/2023 - 10:36

      Seems to be the case. $350 from Merc. The genuine was the first one to die (within 90k km). Two since. I was suss that 3 have died. But maybe the cheapies just arent up to being so close to the turbo outlet.

  • Malik Nasser on 03/07/2023 - 09:25

    Possibly an electrical issue in your system. If it is receiving a voltage that is above the rated voltage, then it will burn out.
    As you have had issues with multiple sensors, then I would think it is becoming less likely to be a sensor issue, and more likely to be an environmental issue (exposed to conditions outside of its design rating).
    If you don't resolve the root cause, then replacing the sensor again may just result in another failed sensor a couple of months down the road.
    Might also want to test your battery, if it is running low it could cause your computer to kick up some funky codes.

    • tunzafun001 on 03/07/2023 - 10:39

      Yeah, my thinking is along this line. Its a 5v sensor, and receives 5v when checked. Not that I can guarantee it is 5v all the time. Sensor is open circuit when it throws a code, so its definitely a warranted code.

  • thesilverstarman on 03/07/2023 - 10:18

    "So my parents merc diesel threw an egt sensor failure code" No it did not. It would have shown a code for the sensor. Scan tools do not tell you the part that is faulty. It is poor mechanics to change a part based on a scan. What the scan tool told you is that there is a problem that is showing a symptom. The mechanic then needs to look at why and what the problem is. Does the ECU make this circuit open when it goes into limp mode? Is it reading a figure too high so this input is disabled? Supercheap will scan a car. They also sell heaps of exhaust sensors, because that is a common code, but the problem is rarely the exhaust sensor. This is the equivalent of a person saying that they have a sore foot, so having it amputated, when a professional (a doctor) would do further examination and might find that the problem is diabetes.
    Take it to someone who knows what they are doing. There could be many causes, but listing them is useless because to accurately diagnose would need the car in front of me, proper scan tools (generic and cheaper tools do not read all codes and do not read them all accurately for many brands) and of course someone with the knowledge and experience to interpret those codes.

    • tunzafun001 on 03/07/2023 - 10:50

      Thanks for the input. The scan tools in this case do say exactly what is wrong and where.
      The car does go into limp mode when the sensor goes open circuit. This simulates the temp being 1200C at the EGT (also observable with a scan). However, we took it to Merc for a full scan read out to see if there was anything else.
      It gave out the same scan tool message, word for word. The only other thing it picked up was a short to positive with one of the door handles..which is odd as they work fine.
      Their solution was to simply replace the EGT again, at a cost of about $1000. My parents are just pensioners. Never should have bought a Merc, but always wanted one.

      It could simply be 3 rubbish EGTs, but its a bit of a fool me twice situation.

      Reseaching online with people with multiple EGT failures results in no solution (people replace full harness/ ecus with no change). A few posts above is pretty standard. I think its a fuel delivery thing (over heating the egt). It always dies on an uphill 100km per out section..

      BUT..there are no other fault codes thrown. Ie lean sensor etc

      • Protractor on 03/07/2023 - 10:55

        Is the exhaust blocked? Turbo healthy? MAF OK? Have the alternator checked.
        And redo as many earthing /grounding points as you access.

        • tunzafun001 on 03/07/2023 - 11:59

          I was thinking this. But don't think it would kill a an egt (open circuit)?

      • thesilverstarman on 03/07/2023 - 12:49
        +1

        Did you disconnect the battery before replacing it? And reconnect with the negative first? You didn't over tighten when installing? You removed wiring plug before removing /installing to make sure that you didn't twist or break wires?
        You can confirm readings using a temp gun, and compare to what you are seeing from the sensor.
        With vehicle ignition turned on, and the plug on the EGT sensor disconnected, measure the voltage at the sensor’s connector – there should be 5 volts. If not, then trace the wire back to the ECU and check supply there.
        Also check the pre-cat sensor and see if the readings are correct.
        The DPF could be blocked, but may not be regenerating properly. Drop it and check. See if you can do a manual regen with scan tool.
        Without seeing it, it sounds like the exhaust is heating up too much. DPF regens are not as simple as driving on the freeway for a bit. Incorrect oils that are high ash producing can make this worse.
        My records show that a DPF regeneration only kicks in when your engine is operating at 2,000RPM or more and you’re travelling at 80km/h or more for a continuous period of at least 15 minutes. Then it has to continue to do so, and complete. If not complete, it will keep injecting fuel to increase temp to burn off when restarted. The rpm will be less than this on the freeway, so you need to manually drop it back a gear or 2 to keep the revs up.
        The sensors will always break if overheated. This sounds to me like an issue caused by regen, which could be caused by incomplete regens, incorrect readings from the other sensors, or even the injection system to the exhaust.
        Source - mechanic specialising in Mercs.

        • tunzafun001 on 03/07/2023 - 13:12

          Brilliant mate. Thanks for the extended response. First part all good. Ie. 5v present. Sensors all function properly when first installed (observed temp readings of 200-300c on idle/ revs).

          But died both times when going up a decent hill at 100km/h. Goes into limp mode. Sensor is open circuit / toast.

          Will explore DPF, and maybe an upstream sensor. Do recall seeing an upstream egt was out of range and positive to ground a while back. But all went away when the egt just under the turbo is replaced.

          ×edit - the upstream positive to ground error has come back. But goes away whe you plug in what I would consider a downstream EGT (ie. Under the turbo)?

        • tunzafun001 on 03/07/2023 - 16:02

          *edit 2 - never mind. Re looked at the exhaust, this faulty EGT is indeed the upstream from the turbo EGT.
          Not sure about the short to positive error message though (2 sensors give this error message)-
          1 EGT is the "new" ali express one (which is now open circuit between the two sensor wires).
          2 The older SKV one is only open circuit once it gets warm. But both return the short to positive message.
          Perhaps its just a generic error message?

          I did notice a split in the crank case recir tube nearby. Dont think that will be the cause, but just thought id note it.

  • Drakesy on 03/07/2023 - 11:00
    +2

    Yeah Diesel Euro's are a PITA to maintain.
    Unless you're in the country or doing repeated hwy hauls >30 mins i'd stick to a petrol.

    Is the DPF/EGR all working fine and whats the carbon build up like>, are you finding the sensors getting clogged or burning up?

    • Protractor on 03/07/2023 - 11:13
      +1

      Was thinking EGR myself. And this things is slugging out uphill.
      I think too many ppl rely on waiting for cars to throw codes (which are often wrong) rather than physically trace and diagnose related or upstream 'causal' factors. Some codes are wild geese.

      • tunzafun001 on 03/07/2023 - 11:51

        Definitely not sluggish uphill. But it obviously is once going into limp mode. EGT goes open circuit.

    • tunzafun001 on 03/07/2023 - 11:49

      Sensors came out very clean. So no issues there. Their commute is regular 100km/h stretches. I did find a crack in a rubber tube coming from crank case ventilation. But don't Think that would impact this.

  • Protractor on 03/07/2023 - 11:31
    +1

    Buy a 6 pack of them>

    https://www.rockauto.com/en/catalog/mercedes-benz,2012,gl350,3.0l+v6+diesel+turbocharged,1503191,exhaust+&+emission,exhaust+gas+temperature+(egt)+sensor,17051

    • tunzafun001 on 03/07/2023 - 11:57

      Cheers, if I had to do 6 I'd also need a blood transfusion from loss of blood at the knuckles. This is a reach to the back tip of your finger type job.

      P.S. it's the $67 exhaust one at the bottom. But becomes $104 when you put it in your cart.
      Walker any good?

      • Protractor on 03/07/2023 - 17:15

        Not sure, about Walker, but Americans buy them, and Americans have guns. Join the dots
        It's highly likely that the cheapest on the Rockauto list is still better than knockoffs you have thus far killed.
        My 6 p[ack comment was related to the price per Merc pricing. Once you get an OEM number you can spend some time online finding a reputable named alt sensor source. Maybe NGK, Bosch etc?

        I'd still be ruling out the extensive list posted further up(several ppl) .(Inc alternator behaviour )
        Parts are listed in US unless you select AUD, that might be auto happening at trolley or checkout
        Hence the price diff. Postage is the heavier load these days so try to stock up on some other stuff while you are there & save some cash.

  • tunzafun001 on 16/11/2023 - 18:17

    Hmm… curse strikes again!!

    Anyone know this recall didn't happen in OZ?
    https://www.consumerreports.org/emissions/mercedes-benz-dies…

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