# 2018 diesel regen



## 406 (Apr 5, 2019)

Jenlee1986 said:


> Does anyone know how often the car is supposed to do a regen? In driving 17 miles on the highway, at 75 mph, my car did a regen at least 5 times. I brought it to the shop when I found out about the recent recall for the regen about 2 months ago. My car has just over 10,000 miles on it.



The longest I've been able to go is about 800 miles before one is forced.


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## Jenlee1986 (Apr 15, 2020)

When it does the regen and your watching the instantaneous mileage it will drop your mileage way down right?


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## MRO1791 (Sep 2, 2016)

Jenlee1986 said:


> Does anyone know how often the car is supposed to do a regen? In driving 17 miles on the highway, at 75 mph, my car did a regen at least 5 times. I brought it to the shop when I found out about the recent recall for the regen about 2 months ago. My car has just over 10,000 miles on it.


Without a monitor it is a bit of a guess to know when it is in regen, but yes, an MPG drop is a sign, though MPG can also drop for many other reasons as well, so it's not for sure. Generally I see between 250-1000 mile between regens. I do have a monitor that tells me when it goes into regen (BiScan for GM with Torque Pro app on my phone), and for how long, and tracks the distance between. The new recall is to enable a check engine light ( the technical term is: MIL - malfunction indicator lamp) if you are getting regens too frequently, which would be a sign something is not right.


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## MRO1791 (Sep 2, 2016)

Jenlee1986 said:


> Does anyone know how often the car is supposed to do a regen? In driving 17 miles on the highway, at 75 mph, my car did a regen at least 5 times. I brought it to the shop when I found out about the recent recall for the regen about 2 months ago. My car has just over 10,000 miles on it.


Oh, one other note, a typical regen will take about 10-20 minutes, and it will be interrupted if you let of the throttle too long (like a big downhill run), and also if you put on the throttle too hard, (like a big uphill run). If the regen is interrupted, it will take longer to complete. Reading your post again, it sound like you had one regen that has some interruptions, not separate regens, that is it might have not completed in 17 miles at that speed, so could have been close to complete but not finished. 
During the regen, the ECU is controlling many parameters to hit about 1200F in the DPF (I've seen it go as high as 1240F). That is really close to the melting point of some of the metals in the system, and that is needed to get a good clean of the DPF, if there is little load on the engine, it has problems keeping the temperature up, and interrupts, if there is load, it has to stop or it will go too high in temperature, which is why best case for a good regen is constant highway speed, level ground, that lets the process complete the fastest and be the most complete. This is also why frequent short city drives are so hard on these cars with this kind of system. It never gets a chance to properly clean the DPF, and all kinds of other problems can pop up in those cases.


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## plano-doug (Jul 1, 2015)

MRO1791 said:


> ... which is why best case for a good regen is constant highway speed, level ground, that lets the process complete the fastest and be the most complete.


Too bad there's not an option for manually inducing a regen, if you see a good opportunity during a long drive. Sort of like changing the oil a little early, why not be able to start a regen a little before it's due?

Doug

.


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## phil1734 (Aug 30, 2019)

I think OP is seeing a regular fluctuation of instantaneous MPG and mistaking it for a regen cycle.


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## Jenlee1986 (Apr 15, 2020)

MRO1791 said:


> Without a monitor it is a bit of a guess to know when it is in regen, but yes, an MPG drop is a sign, though MPG can also drop for many other reasons as well, so it's not for sure. Generally I see between 250-1000 mile between regens. I do have a monitor that tells me when it goes into regen (BiScan for GM with Torque Pro app on my phone), and for how long, and tracks the distance between. The new recall is to enable a check engine light ( the technical term is: MIL - malfunction indicator lamp) if you are getting regens too frequently, which would be a sign something is not right.


I'm still learning about the regen and stuff, my husband d knows alot more than I do about diesels. But this is our first diesel that takes def and does regens. Last night on my way home my check engine light did come on, going to run diagnostic on it shortly to see why.


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## Barry Allen (Apr 18, 2018)

plano-doug said:


> Too bad there's not an option for manually inducing a regen, if you see a good opportunity during a long drive.


I have noticed that when I'm doing highway driving, I occasionally stop to fill the fuel tank. Immediately after pulling back onto the highway my car will go through at least a short regen cycle. It's a guess, but I believe the ECU has some programming that will start a regen if you fill the fuel tank on a hot car (up to operating temperature) and then take it to highway speed.


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## 406 (Apr 5, 2019)

I highly recommend anyone with regen concerns get this app Gretio and a good OBD reader for their car. Otherwise, everyone on the forum is just guessing based on broadly described symptoms... With this there are no more questions about "Am i having a regen?" " Why am I having a regen?" "How often should I be having regens?" (Which depends on a plethora of things...)


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## MRO1791 (Sep 2, 2016)

plano-doug said:


> Too bad there's not an option for manually inducing a regen, if you see a good opportunity during a long drive. Sort of like changing the oil a little early, why not be able to start a regen a little before it's due?
> 
> Doug
> 
> .


There is a way.. I have the BiScan for GM, and with Torque Pro, I can command a regen when it's close. I can also do a service regen, and other functions.. all from my phone.


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## Jenlee1986 (Apr 15, 2020)

I called onstar and they did a diagnostic on it and they wouldn't tell me the code it threw, but it was for the regen and emmsions.


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## BodhiBenz1987 (Jan 13, 2018)

406 said:


> I highway recommend anyone with regen concerns get this app Gretio and a good OBD reader for their car. Otherwise, everyone on the forum is just guessing based on broadly described symptoms... With this there are no more questions about "Am i having a regen?" " Why am I having a regen?" "How often should i be having regens?" (Which depends on a plethora of things...)


I wouldn't describe those with SGII or TorquePro/BiScan as just guessing, since they give most of the same information ... unless you just meant without a scanner it's guessing, which I agree with. Though I don't think any scanner answers "how often should I be having regens?". That's a hard question to answer in general, since it depends on the driving. There is a parameter that comes up on GDS2 for "estimated soot level based on other engine data" (i.e., based on your driving) which I think would probably be the closest thing to a parameter telling you how often your regens should happen, or rather, what your soot level should be which is of course directly related. E.g., my soot level was 97% as measured by pressure diff sensor and my estimated soot level based on engine data was 31% ... which I translate as, I should not be having as many regens, based on engine data. Does Gretio have that parameter? That's probably the biggest one missing from the SGII I'd love to have. Even though GM will never admit there is anything "abnormal" about the numbers, I compile them anyway.

Without a scanner, the best way to tell if the car is in a regen on the highway is looking at the economy bars for a trend. Instantaneous fluctuates too dramatically to be a really dependable measure. Even then you need to be familiar enough with a stretch of highway to know what it normally does, and it needs to be under normal circumstances. 

@406 ... 31 psi boost? Is that right?? Mine only gets up to the low 20s. I though max was 23 psi or so.


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## BodhiBenz1987 (Jan 13, 2018)

Jenlee1986 said:


> I called onstar and they did a diagnostic on it and they wouldn't tell me the code it threw, but it was for the regen and emmsions.


That's kinda odd they wouldn't tell you the code. I will be interested to hear if it is in fact for frequent regens, because I'd love to know where the software sets the bar for that, and what they do to fix it. As MRO mentioned, you might have been having a regen that was failing to complete, rather than frequent completed regens.


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## Jenlee1986 (Apr 15, 2020)

BodhiBenz1987 said:


> That's kinda odd they wouldn't tell you the code. I will be interested to hear if it is in fact for frequent regens, because I'd love to know where the software sets the bar for that, and what they do to fix it. As MRO mentioned, you might have been having a regen that was failing to complete, rather than frequent completed regens.


I'm pretty sure my car is doing constant partial regens. But I drive about 17 miles at 78 mph, then I drive another 15 at 60 mph for work 1 way. I put a good 300+ miles on my car every week. I bought this car with 153 miles in it from a dealer in the beginning of November, and now it has 10,186.


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## BodhiBenz1987 (Jan 13, 2018)

Jenlee1986 said:


> I'm pretty sure my car is doing constant partial regens. But I drive about 17 miles at 78 mph, then I drive another 15 at 60 mph for work 1 way. I put a good 300+ miles on my car every week. I bought this car with 153 miles in it from a dealer in the beginning of November, and now it has 10,186.


If everything is functioning correctly it sounds like you do enough highway it shouldn't have a problem completing the regen, so it sounds like something is amiss for sure ... at least with the CEL coming on the dealer will have a good start for diagnosing. If you can, please report back the codes and how it gets resolved, which hopefully they can do quickly for you.


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## Barry Allen (Apr 18, 2018)

BodhiBenz1987 said:


> 31 psi boost? Is that right?? Mine only gets up to the low 20s. I though max was 23 psi or so.


I had the same question. A couple years ago I read both the Motor Trend and Car & Driver tech review of the GM Medium Diesel Engine. Specs from both articles was listed as peak boost of 27psi.


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## Snipesy (Dec 7, 2015)

They may be confusing MAP and boost. Happens all the time. Boost is roughly MAP-14psi depending on elevation.

Also depends where the boost reading sensor is. Usually it’s the MAP but there is other pressure sensors.


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## Jenlee1986 (Apr 15, 2020)

BodhiBenz1987 said:


> If everything is functioning correctly it sounds like you do enough highway it shouldn't have a problem completing the regen, so it sounds like something is amiss for sure ... at least with the CEL coming on the dealer will have a good start for diagnosing. If you can, please report back the codes and how it gets resolved, which hopefully they can do quickly for you.


I'm going to drop it off tomorrow hopefully to the dealer. I will let you know what I find out.


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## BodhiBenz1987 (Jan 13, 2018)

Barry Allen said:


> I had the same question. A couple years ago I read both the Motor Trend and Car & Driver tech review of the GM Medium Diesel Engine. Specs from both articles was listed as peak boost of 27psi.


 I thought I remembered reading something along those lines. I think the most I have seen on my gauge is 23 or so. I have the gauge sitting in the console so it's hard to safely look at the boost when I'm really pushing the car (which I don't often anyway). Also the SG seems to have a bit of a delay so the numbers kind of flash rather than being linear. 

@Snipesy that would make sense. I think when I first set up my ScanGauge it had the MAP reading before I adjusted it to show a boost parameter. I don't actually know where the reading is taken, I thought maybe it was the same sensor with the reading adjusted.


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## 406 (Apr 5, 2019)

Barry Allen said:


> I had the same question. A couple years ago I read both the Motor Trend and Car & Driver tech review of the GM Medium Diesel Engine. Specs from both articles was listed as peak boost of 27psi.


It doesn't usually hold steady in the 30's, happen to take the snapshot during a downshift so the boost spikes. And if your not looking at the PIDs for regen status, reason, count, so on, you're guessing


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## BodhiBenz1987 (Jan 13, 2018)

406 said:


> And if your not looking at the PIDs for regen status, reason, count, so on, you're guessing


As long as you have regen status, EGTs, and soot percentage, you know when it's doing a regen. I don't have the reason or total count. There are only four reasons: soot %, distance, commanded regen, and service regen. Every regen I have had since I got the ScanGauge a year ago has been because the soot % hit 100%, so I don't really need the reason feature. It's possible that early on I had some like yours that went on distance before whatever is broken on mine broke, especially since I did a couple serious road trips in the first few months. Total count would be nice but I keep a notebook and write down when I observe them. I've also had that number (and all the other numbers) pulled three times by the dealer so that I have a hard record of everything.


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## MRO1791 (Sep 2, 2016)

Jenlee1986 said:


> I'm pretty sure my car is doing constant partial regens. But I drive about 17 miles at 78 mph, then I drive another 15 at 60 mph for work 1 way. I put a good 300+ miles on my car every week. I bought this car with 153 miles in it from a dealer in the beginning of November, and now it has 10,186.


Your driving profile should be a good fit for this car, plenty of highway time to clear out the DPF and keep the emissions happy. Keep us posted on what they find. OnStar won't provide much information, as I don't think their advisers know much about the information they get from the car scan, but always be specific to ask for the specific CODE that the scan provides. All check engine light (CEL or MIL) light conditions have a code associated with them. This is also called a DTC in some places, which is a Diagnostic Trouble Code. This is a starting point to figure out what is going on. The entire table can be found online, and from that code some of us here can get pretty close to knowing what is going on, I've used it several times on my fleet of vehicles, and I often tell the servicing dealer what is needed before they even scan the car!


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## 406 (Apr 5, 2019)

BodhiBenz1987 said:


> I don't have the reason or total count.


The reason might be a good starting point considering your guesses over the course of a year have led nowhere.


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## 406 (Apr 5, 2019)

MRO1791 said:


> Your driving profile should be a good fit for this car, plenty of highway time to clear out the DPF and keep the emissions happy. Keep us posted on what they find. OnStar won't provide much information, as I don't think their advisers know much about the information they get from the car scan, but always be specific to ask for the specific CODE that the scan provides. All check engine light (CEL or MIL) light conditions have a code associated with them. This is also called a DTC in some places, which is a Diagnostic Trouble Code. This is a starting point to figure out what is going on. The entire table can be found online, and from that code some of us here can get pretty close to knowing what is going on, I've used it several times on my fleet of vehicles, and I often tell the servicing dealer what is needed before they even scan the car!



I'll second this as being adequate distance, time, speed to keep the emissions equipment as healthy as possible, I have a very similar commute. One point I'll add, DO NOT start this car and let it warm up for ten minutes, or leave it idling while you run into the store, so on. Start it, idle for 30-60 seconds, and make your trip. Shut her down when you get there. Idling is horrible for the emissions equipment.


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## BodhiBenz1987 (Jan 13, 2018)

406 said:


> The reason might be a good starting point considering your guesses over the course of a year have led nowhere.


Well I'm planning to get the blutooth/app setup soon anyway, so we'll see what it says. But I think it's a pretty solid Occam's razor that if the soot level reading is at 100%, and the system is designed to initiate a regen when that reading reaches 100%, the regen was initiated by the soot level reading. The thing I really want/need to know, which I have been wildly guessing at, is why the soot level is reaching 100% so fast. Unless I am misunderstanding the PID, it would only tell me what the trigger of the regen is, rather than what is causing the trigger itself.


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## 406 (Apr 5, 2019)

BodhiBenz1987 said:


> Well I'm planning to get the blutooth/app setup soon anyway, so we'll see what it says. But I think it's a pretty solid Occam's razor that if the soot level reading is at 100%, and the system is designed to initiate a regen when that reading reaches 100%, the regen was initiated by the soot level reading. The thing I really want/need to know, which I have been wildly guessing at, is why the soot level is reaching 100% so fast. Unless I am misunderstanding the PID, it would only tell me what the trigger of the regen is, rather than what is causing the trigger itself.


You don't know for sure. Your assumptions are just that.


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## FlagrantBacon94 (Apr 8, 2020)

Jenlee1986 said:


> Does anyone know how often the car is supposed to do a regen? In driving 17 miles on the highway, at 75 mph, my car did a regen at least 5 times. I brought it to the shop when I found out about the recent recall for the regen about 2 months ago. My car has just over 10,000 miles on it.


I’m not sure myself but there was a recall for the regen cycle about a couple months ago. It’s supposed to Decrease the amount of regen cycles it goes through.


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## DslGateWon (Apr 8, 2020)

Jenlee1986 said:


> I'm pretty sure my car is doing constant partial regens. But I drive about 17 miles at 78 mph, then I drive another 15 at 60 mph for work 1 way. I put a good 300+ miles on my car every week. I bought this car with 153 miles in it from a dealer in the beginning of November, and now it has 10,186.


I have the 2.0 CTD LUZ, so I am not sure that my situation is similar to your 1.6 (smaller diesel engine), but I have never seen on my Scan Gauge 2 the amount of 5 regens within 17 miles. I have an engine tuner as well , so YMMV, but my shortest time between regens ever is about 100 miles and longest (when car new) was 1200 miles. Now, I average about 500-700 miles between regen on the SC2. Sometimes, if I am doing a LOT of city driving, it'll be 200-400 miles between regens. It regens a LOT less if I am doing a LOT of highway driving. Remember, this is on a 2015 CTD with the 2.0 TD tuner and not the smaller 1.6 . I've had the car almost 6 years so I am very familiar with regens and how often they occur. 5 in 17 miles would be ridiculous. (every 3 miles or so??) . It takes longer than 3 miles to even complete a regen. My regens typically occur on the highway and take at a minimum 10-15 miles of continuous driving before I get a #2 which means Regen completed on the SC2.


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## BodhiBenz1987 (Jan 13, 2018)

@Jenlee1986 , were you able to find out anything from the dealer? Hope they were able to sort it out for you.


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## Skrikel (Apr 25, 2020)

Jenlee1986 said:


> Does anyone know how often the car is supposed to do a regen? In driving 17 miles on the highway, at 75 mph, my car did a regen at least 5 times. I brought it to the shop when I found out about the recent recall for the regen about 2 months ago. My car has just over 10,000 miles on it.


I've been running an OBD monitor since getting my 2018 TD manual. Looking at EGT's alone its once a fuel tank when 95% highway driven. (Bought new and driven 68.xxx km so far)


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## Snipesy (Dec 7, 2015)

All diesels have a historical PID called “Regen Reason”.

In addition some have a pid which will tell you which stage the Regen is actually in. I can’t remember if the 1.6L has that or not.

Newer diesels also do more frequent burns. These aren’t regens but help keep the exhaust clean of soot, urea, and other junk. Possibly even help catalysts reach operating temps quicker.


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## BodhiBenz1987 (Jan 13, 2018)

Snipesy said:


> All diesels have a historical PID called “Regen Reason”.
> 
> In addition some have a pid which will tell you which stage the Regen is actually in. I can’t remember if the 1.6L has that or not.
> 
> Newer diesels also do more frequent burns. These aren’t regens but help keep the exhaust clean of soot, urea, and other junk. Possibly even help catalysts reach operating temps quicker.


During a regen on the SGII mine will display a 6 right when it starts and then a 7 during the regen (0 all other times) ... so I assume the 6 is the warmup stage. I have not seen a number other than those so I do not know if it will show other stages.
I do notice when I first start off driving it will do a little cycle where the EGTs go up to around 800 ... the regen status stays the same during these (0), so I assume these are the burns helping the catalysts reach temp and clear out anything. They don't last long, a few seconds.
I bought an ODBLink MX to try Gretio, just haven't had a chance to set it all up.


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## Jenlee1986 (Apr 15, 2020)

BodhiBenz1987 said:


> @Jenlee1986 , were you able to find out anything from the dealer? Hope they were able to sort it out for you.


So I got the email from OnStar about the code. The code that came up was P11DC. In their description it said it was the exhaust emissions system. 
When I brought my car to the dealer I told them what code OnStar said it was. When I got it back they told me they changed the 'knock sensor'. They said that was preventing the car from doing a regen. 
I've had it back for about a week now, so we'll see if the check engine light comes back on or not.


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## Jenlee1986 (Apr 15, 2020)

Skrikel said:


> I've been running an OBD monitor since getting my 2018 TD manual. Looking at EGT's alone its once a fuel tank when 95% highway driven. (Bought new and driven 68.xxx km so far)


How much louder is your car since you bought it? When I bought mine you couldn't hear it run, let alone unknowingly know it was a diesel. Now it is about 4 times louder. I didnt think it would get as loud as it is.


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## Skrikel (Apr 25, 2020)

Well personally I love the sound of a diesel. I actually removed a tonne of sound deadening in the engine bay as well as around the common rail and injectors. So to answer you yes its gotten louder but that was what i wanted.


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## Carminooch (Mar 23, 2018)

Jenlee1986 said:


> So I got the email from OnStar about the code. The code that came up was P11DC. In their description it said it was the exhaust emissions system.
> When I brought my car to the dealer I told them what code OnStar said it was. When I got it back they told me they changed the 'knock sensor'. They said that was preventing the car from doing a regen.
> I've had it back for about a week now, so we'll see if the check engine light comes back on or not.


Can you tell me how long it took and where you brought your vehicle?

I’ve been waiting over three weeks for the nox sensor to correct my P11DB and have been told since it’s coming from Michigan, the warehouse is being staffed with volunteers to ship orders and that there’s no eta. It’s been over 3 weeks. I might be close to week 4 now who knows


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## Jenlee1986 (Apr 15, 2020)

I brought my car in in Friday and they said the part would be there Tuesday. It ended up being done on Monday.


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## Jenlee1986 (Apr 15, 2020)

I just brought it to the Chevrolet dealership. Since my car is still under warranty I have been bringing it there and making them fix everything.


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## Barry Allen (Apr 18, 2018)

Jenlee1986 said:


> When I got it back they told me they changed the 'knock sensor'


Did you ask them if they changed the spark plugs as well?


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## Jenlee1986 (Apr 15, 2020)

They did not. They said all they did was change the knock sensor.


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## cdccjohnson (Apr 10, 2018)

Barry - diesels dont have spark plugs.


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## Barry Allen (Apr 18, 2018)

cdccjohnson said:


> Barry - diesels dont have spark plugs.


I know. Does a diesel engine have a knock sensor?


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## Carminooch (Mar 23, 2018)

Jenlee1986 said:


> They did not. They said all they did was change the knock sensor.


Ah I think you mean “NOX” sensor since it’s pronounced the same.

I’ve been waiting a month for one, how did you get yours so quickly? Can you message me the dealership you went to, to see if they can order me one?

My dealership and GM Sr advisor working with me both say that there’s no eta because it’s coming from Michigan and the parts warehouse hasn’t been staffed


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## Barry Allen (Apr 18, 2018)

Carminooch said:


> Ah I think you mean “NOX” sensor since it’s pronounced the same.


That's probably correct and I didn't think of that.

I was asking a rhetorical question (about spark plugs) because if a mechanic ever told me that the knock sensor on my diesel engine needed replaced, I'd have a good laugh about that the same as any shop that told me I needed spark plugs replaced in a tune-up.


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## MP81 (Jul 20, 2015)

Barry Allen said:


> That's probably correct and I didn't think of that.
> 
> I was asking a rhetorical question (about spark plugs) because if a mechanic ever told me that the knock sensor on my diesel engine needed replaced, I'd have a good laugh about that the same as any shop that told me I needed spark plugs replaced in a tune-up.


Kind of like how I laughed, at first, when my buddy said the shop he took his Cobalt to recommended a power steering fluid flush. 

On a car with EPS.


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## Cruz15 (Mar 17, 2016)

Carminooch said:


> Ah I think you mean “NOX” sensor since it’s pronounced the same.
> 
> I’ve been waiting a month for one, how did you get yours so quickly? Can you message me the dealership you went to, to see if they can order me one?
> 
> My dealership and GM Sr advisor working with me both say that there’s no eta because it’s coming from Michigan and the parts warehouse hasn’t been staffed


Do you know the part#?


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## Carminooch (Mar 23, 2018)

Cruz15 said:


> Do you know the part#?


There are two but the part number for the one I need is:

55503927

Found it in PA after calling around a bunch of places but senior Chevy advisor says “we don’t do that, they’re independently run”, my dealership said “uh can they do that?” and the other dealership said “yeah all they have to do is call us”

It’s been over a week and nothing. No parties will cooperate


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