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Discussion Starter · #1 ·
Just the facts and nothing but...

I have a 2017 chevy Colorado Z71 with 2.8 Diesel. Love it! but here is the spat it and I had.

3 weeks ago I drove 600 plus miles and it went through 3 times the normal DEF, coincidently the AC would not blow cold air on the return part of my trip for about 20 miles.. I played with the buttons every which way, the only way it would blow cold was running fan full blast. finally I shut of AC completely and started up again and it worked fine. I thought nothing of it already knowing that the radio/media player plays what IT wants to play every once in awhile. everything is good so out of mind right! ? hmmm nope.... on this next trip a few days ago after driving 250 miles I get check engine light, truck is running fine, all looks good on the onboard dash display... stop at Autozone and use their scanning and it shows P24B0, quick check by their sales guy tells me dealer only part... a sensor is needed should not be expensive and easy fix. So I start calling dealerships around the area, after speaking with 3 I stopped calling them, they all said same thing.... we are too busy, min of 2-3 days and one said a week, JUST TO ACCEPT the vehicle for them to look at and ALL said it was a complicated job. Well that sucks ! so I called up an independent diesel mechanic I know from way back (I used to live in this area for a very long time) He worked on my first diesel eve... now that was love.... 1989 ford van with 7.3 ... those of you that know the engine will know what im talking about. Anyways, my friendly mechanic tells me bring it on by, maybe he can clear the code... I went and what he did was force a regen cycle... now this is where it gets interesting....

Forced Regen cycle, engine rpm at 2500 for about 20 min. did a few more functions on scanner and error was gone, have since driven about 400 miles all is well.

Now when I have noticed self induced regen cycle while I am driving, its always been on highway... however even at 75 mph the rpm is at around 2000-2100.

SO! im asking mechanic whats the deal... he explains that a forced regen cycle is good idea and that other diesel owners with similar setups force regen periodically. well this is news to me... and I thought I did my homework!.

So who out there is forcing regen cycles.. I would like to hear how often and what scanning tool you use.. cause im not exactly liking the idea of spending $1000 plus for a scanner that will do this function... AND is it easy to use... what other steps do you need to take after the forced regen, ( my friendly mechanic said he would teach me for a fee ).
 

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if the code was legitimate, itll likely come back - according to the manual im looking at P24B0 is for a PM sensor low voltage.

The particular matter sensor control unit detects an internal fault of the sensor, fault of the sensor
circuitry, or low voltage on the sensor supply circuit.



if youre doing a lot of stop and go, short cycle driving, it would be a good idea to force a regen periodically. though the system should be smart enough to catch this and warn you eventually.
doing it just to do it isnt going to hurt anything but youre likely not burning anything off that wasnt going to be burned off in a 20-30min highway drive
 

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Discussion Starter · #3 ·
if the code was legitimate, itll likely come back - according to the manual im looking at P24B0 is for a PM sensor low voltage.






if youre doing a lot of stop and go, short cycle driving, it would be a good idea to force a regen periodically. though the system should be smart enough to catch this and warn you eventually.
doing it just to do it isnt going to hurt anything but youre likely not burning anything off that wasnt going to be burned off in a 20-30min highway drive
2-3 times a month i drive 500 miles plus on interstate highway, about 75 % of my driving, remaining is about another 15% at home highway and 10% stop n go city driving. Mechanic did force a regen cycle (since then I have driven about 400 miles, no return of code).

My understanding is this sensor measures soot. so was there too much soot and it triggered code? if so why didnt it just enter a regen cycle ? regardless the mechanic got me going again by forcing the regen cycle. what was interesting is by using his scan tool to engage the vehicles computer to start the regen the RPM was up at 2500, as opposed to regen cycle while driving on highway RPM at 2100-2200. So what i want to know from folks out there is any one else doing a periodic Forced regen as part of their routine maintenance, this is what mechanic told me to do as it is what big rigs driver do with their trucks. FYI mechanics reasoning was that a forced regen uses less fuel in combustion chamber as vehicle is parked and in neutral, no load on engine, with less fuel going to combustion chamber less soot created while the regen cycle is engaged which gives a better result of cleaning DPF.
 

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My understanding is this sensor measures soot. so was there too much soot and it triggered code?
no, because again the code is specifically for a voltage issue related to the sensor. theres a different code for PM sensor performance. maybe it was a fluke or some intermittent connection issue. but if that was the code - again as you can see from the diagnostic procedure - its purely electrical.

what was interesting is by using his scan tool to engage the vehicles computer to start the regen the RPM was up at 2500, as opposed to regen cycle while driving on highway RPM at 2100-2200.
you need more mass flow to generate the heat needed when the engine doesnt have any load on it.

So what i want to know from folks out there is any one else doing a periodic Forced regen as part of their routine maintenance, this is what mechanic told me to do as it is what big rigs driver do with their trucks.
they have the option of initiating that stationary regen with a button press when the soot loading gets high enough, but again that would only happen with a drive cycle that wasnt conducive to over the road regens.

FYI mechanics reasoning was that a forced regen uses less fuel in combustion chamber as vehicle is parked and in neutral, no load on engine, with less fuel going to combustion chamber less soot created while the regen cycle is engaged which gives a better result of cleaning DPF.
though that sounds somewhat logical, thats not exactly how it works
in fact there is extra combustion chamber fuel used during that stationary regen in order to generate the heat needed. again because of the reduced mass flow since the truck is sitting without load.

you dont have to take my word for it though, here is what the factory says about regen cycles.




a clean dpf is a clean dpf, the system can tell when its empty based on the differential pressure.
 

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Discussion Starter · #5 ·
no, because again the code is specifically for a voltage issue related to the sensor. theres a different code for PM sensor performance. maybe it was a fluke or some intermittent connection issue. but if that was the code - again as you can see from the diagnostic procedure - its purely electrical.



you need more mass flow to generate the heat needed when the engine doesnt have any load on it.



they have the option of initiating that stationary regen with a button press when the soot loading gets high enough, but again that would only happen with a drive cycle that wasnt conducive to over the road regens.



though that sounds somewhat logical, thats not exactly how it works
in fact there is extra combustion chamber fuel used during that stationary regen in order to generate the heat needed. again because of the reduced mass flow since the truck is sitting without load.

you dont have to take my word for it though, here is what the factory says about regen cycles.




a clean dpf is a clean dpf, the system can tell when its empty based on the differential pressure.
interesting indeed... then I am going along with what i originally thought... it is electrical issue... the vehicle has issues every blue moon, as i posted earlier... the AC issue, the radio issue (which i get often) and now this code... as the autozone sales guy said, its a senor that may need to be replaced, but its dealer only part. I will see if my local mechanic can order the part and replace.

Thanks for the info!
 

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no problem!
if the parts not easily available or real spendy, and you said youve driven a few hundred miles without issues... maybe wait to see if it comes back. if it becomes less intermittent itll likely be easier to chase down. most of those downstream sensors are really easy to get to if youre inclined to DIY.

ive got a tuned '18 with just shy of 60k that within the last couple months will have had both nox sensors replaced. **** happens i guess :) thats the price to pay for driving a rolling science experiment.

ive had great luck with getting stuff from gmpartsdirect but theres a ton of dealers that have online sources if you can get the p/n
 

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Discussion Starter · #7 ·
The More I dig the more im not happy...https://static.nhtsa.gov/odi/tsbs/2017/MC-10135154-9999.pdf looks to me like the ECM needs to be programmed, I did receive the recall notice to get it re-programmed, but i really dont want to... I dont trust dealerships here at all! Everyone I know who takes their vehicles to dealerships say they get hosed one way or another. or their vehicle starts failing in other ways.
 

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Go under there and give the sensor a plug and unplug deal. I had issues with my PM sensor and I went to replace it only to find that the old one was seized in place. I heated it, beated it, cooled it, plugged it and unplugged it. Eventually gave up on replacing it and went to drive away and CEL was off and hasn't been back for 15K. Idk which of them did it, but plugging and unplugging is easy to try.

The PM sensor has a sensor component which is threaded into exhaust and a computer unit which is plugged in to sensor and car. Be careful with connectors but try unplugging/replugging both connectors.

Sensor is the last sensor in the exhaust line, near the rear axle.
 

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My 2017 had the same issue 3-4 times before 18K miles. Each time diagnostics showed a sensor, the dealers (plural)lacked the diesel skills to fix it and limp mode was scary. I first purchased an android tablet, loaded torque and biscan so I could diagnose and regen myself. I ordered a sensor on rock auto, replaced the sensor and performed a regen. Happy to say 40k later and not even one more issue. I believe that the dealers were cleaning (there is a process on-line) the sensors and re-using the same sensor. Anyway if the dealer is your greatest hope trade for a ford.....
 

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Discussion Starter · #10 ·
My 2017 had the same issue 3-4 times before 18K miles. Each time diagnostics showed a sensor, the dealers (plural)lacked the diesel skills to fix it and limp mode was scary. I first purchased an android tablet, loaded torque and biscan so I could diagnose and regen myself. I ordered a sensor on rock auto, replaced the sensor and performed a regen. Happy to say 40k later and not even one more issue. I believe that the dealers were cleaning (there is a process on-line) the sensors and re-using the same sensor. Anyway if the dealer is your greatest hope trade for a ford.....
well i purchased my 2017 in 2019 used from a dealership with 27K, No issues till 55K miles... well i do have the radio issues on and off.... and the AC issue was a first time. I still think the complicated electronics and ECM programming is an issue with modern vehicles...and it could very well be the issue I am experiencing... after regen (now 500 plus miles) no error code. AND and this is a big AND.... the GM recall is to fix program error that incorrectly reads sensor.
 
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