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Discussion Starter · #1 ·
OK so... I've come across a lot of references to this issue. Has anybody EVER gotten a straightforward solution?

Also, I was informed by a GMC service manager that despite being solely emissions-related, and throwing Emissions codes when there's a problem, GM classifies the DEF delivery hardware to be part of the "Fuel System", not the "Emissions System", and is therefore ONLY covered by the B2B warranty, not the Emissions system warranty.

As a foreword, I have been working 12-15 hours a day, 7 days a week since mid-december, so getting my truck to the dealership hasn't been possible until this week.

I started getting the CEL and 65mph countdown this past winter. Scanner always showed two codes; P20BE, and B20BE (permanent). Reductant heater B performance. It only ever happened when the truck sat out in temps 12°F or less (the freezing point of DEF).

Normally if the DEF lines froze overnight, the truck should upon startup examine the ambient temperature and determine that the DEF heaters need to be on. This process tells the computer to ignore the NOX readings for a little while, because obviously frozen DEF isn't going to flow. Now, the heaters SHOULD be able to thaw the system in a given (unknown) amount of time, and get things flowing.

Anyway, I would get the P20BE CEL and code a few miles into my commute. The countdown would come on and stay on. Again typically, if the computer detected that the problem had been resolved, it's supposed to cancel the countdown. If it got up into the 30° range during the day, when I would go to leave, the CEL and non-permanent P20BE would disappear upon startup. If not, it stayed, and the mileage countdown continued.

That's when I started parking inside the shop while I was at work. Once the truck was all warm and thawed out, I could start it up and the code would disappear. Didn't matter if it was -10° out, everything would work 100% a-ok on the hour long drive home with no codes.

This repeated over and over throughout the cold part of winter, until recently, when it froze up at night and thawed out during the day, the CEL went away, but the countdown didn't. Scan tool still only showed the P20BE (permanent) code. Eventually the countdown ran out and I had no choice but to get in to a shop.

This is where it gets sort of weird.

I pulled in at the dealership a few minutes before they opened, so I plugged in my scanner. There it was still, that lone P20BE (permanent). Pulled it in, explained what was going on to the service rep (who wasn't listening anyway), signed the paperwork, got my loaner and left. A few hours later they call and tell me there's absolutely nothing wrong with my truck. No explanation why the Countdown ran out, no codes whatsoever on the computer. Not even the permanent code.

Now apparently, there's a procedure called an "Emissions tamper test" that runs through and verifies the function of every single component in the system one by one. THIS TEST IS HOW THEY RESET THE COUNTDOWN AND/OR SPEED LIMITER for those of you who have been told they cannot do that. Granted, it only works if everything tests out as functional, and cannot be used to disable the speed limiter say, while you wait a week for parts to come in. But the whole "wait for a regen" or "x number of drive cycles" story is BS. If your problem has been repaired, it will pass the ETT and the countdown/limiter will go away.

Anyway, they ran an ETT and everything checked out. The test computer turned on the DEF heaters, and confirmed the proper 3 amp draw for Heater B and 8 amp draw for heater A. Anyway, everything checked out correctly. Granted, it was being worked on inside a nice warm shop, and it hasn't been cold enough for them to recreate the problem. Speed limit is gone, no codes whatsoever.

Now what I want to know is how does the PCM actually establish whether or not the heaters are functioning correctly? Does it measure the temperature of the DEF at the injector? Obviously it doesn't go by the amp load like the diagnostic computer does, since it appears to draw the correct amount of power when manually engaged.

The diagnostic computer says "heater on" and sees the proper amp draw, "confirming" that the heater works.
The PCM says "heater on", but doesn't see whatever result it's looking for and throws P20BE.

So is the heater really just not heating despite drawing exactly the right amount of current? Ohm's law says no.

Does the PCM think it's turning on the heater, but it's not? Seems unlikely, as there are separate fault codes for no voltage, low current, and excessive current. (P20BD, P20BF, and P20C0)

Is the heater really heating and the PCM isn't detecting it? Again, that would mean the PCM goes by temperature at the nozzle, not by an electrical anomaly.

Is the heater heating and it's just a shitty design that isn't sufficient to thaw a frozen line?

I'm banging my head against the desk here. At least they're only charging me for diagnostics, and not just throwing parts at it and sending me a bill. I doubt we'll have any more cold enough temps this year to do any further diagnostics on it, but that also means I've got 9 months of (hopefully) trouble-free driving ahead of me before I need to worry about it again.
 

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OK so... I've come across a lot of references to this issue. Has anybody EVER gotten a straightforward solution?

Also, I was informed by a GMC service manager that despite being solely emissions-related, and throwing Emissions codes when there's a problem, GM classifies the DEF delivery hardware to be part of the "Fuel System", not the "Emissions System", and is therefore ONLY covered by the B2B warranty, not the Emissions system warranty.

As a foreword, I have been working 12-15 hours a day, 7 days a week since mid-december, so getting my truck to the dealership hasn't been possible until this week.

I started getting the CEL and 65mph countdown this past winter. Scanner always showed two codes; P20BE, and B20BE (permanent). Reductant heater B performance. It only ever happened when the truck sat out in temps 12°F or less (the freezing point of DEF).

Normally if the DEF lines froze overnight, the truck should upon startup examine the ambient temperature and determine that the DEF heaters need to be on. This process tells the computer to ignore the NOX readings for a little while, because obviously frozen DEF isn't going to flow. Now, the heaters SHOULD be able to thaw the system in a given (unknown) amount of time, and get things flowing.

Anyway, I would get the P20BE CEL and code a few miles into my commute. The countdown would come on and stay on. Again typically, if the computer detected that the problem had been resolved, it's supposed to cancel the countdown. If it got up into the 30° range during the day, when I would go to leave, the CEL and non-permanent P20BE would disappear upon startup. If not, it stayed, and the mileage countdown continued.

That's when I started parking inside the shop while I was at work. Once the truck was all warm and thawed out, I could start it up and the code would disappear. Didn't matter if it was -10° out, everything would work 100% a-ok on the hour long drive home with no codes.

This repeated over and over throughout the cold part of winter, until recently, when it froze up at night and thawed out during the day, the CEL went away, but the countdown didn't. Scan tool still only showed the P20BE (permanent) code. Eventually the countdown ran out and I had no choice but to get in to a shop.

This is where it gets sort of weird.

I pulled in at the dealership a few minutes before they opened, so I plugged in my scanner. There it was still, that lone P20BE (permanent). Pulled it in, explained what was going on to the service rep (who wasn't listening anyway), signed the paperwork, got my loaner and left. A few hours later they call and tell me there's absolutely nothing wrong with my truck. No explanation why the Countdown ran out, no codes whatsoever on the computer. Not even the permanent code.

Now apparently, there's a procedure called an "Emissions tamper test" that runs through and verifies the function of every single component in the system one by one. THIS TEST IS HOW THEY RESET THE COUNTDOWN AND/OR SPEED LIMITER for those of you who have been told they cannot do that. Granted, it only works if everything tests out as functional, and cannot be used to disable the speed limiter say, while you wait a week for parts to come in. But the whole "wait for a regen" or "x number of drive cycles" story is BS. If your problem has been repaired, it will pass the ETT and the countdown/limiter will go away.

Anyway, they ran an ETT and everything checked out. The test computer turned on the DEF heaters, and confirmed the proper 3 amp draw for Heater B and 8 amp draw for heater A. Anyway, everything checked out correctly. Granted, it was being worked on inside a nice warm shop, and it hasn't been cold enough for them to recreate the problem. Speed limit is gone, no codes whatsoever.

Now what I want to know is how does the PCM actually establish whether or not the heaters are functioning correctly? Does it measure the temperature of the DEF at the injector? Obviously it doesn't go by the amp load like the diagnostic computer does, since it appears to draw the correct amount of power when manually engaged.

The diagnostic computer says "heater on" and sees the proper amp draw, "confirming" that the heater works.
The PCM says "heater on", but doesn't see whatever result it's looking for and throws P20BE.

So is the heater really just not heating despite drawing exactly the right amount of current? Ohm's law says no.

Does the PCM think it's turning on the heater, but it's not? Seems unlikely, as there are separate fault codes for no voltage, low current, and excessive current. (P20BD, P20BF, and P20C0)

Is the heater really heating and the PCM isn't detecting it? Again, that would mean the PCM goes by temperature at the nozzle, not by an electrical anomaly.

Is the heater heating and it's just a shitty design that isn't sufficient to thaw a frozen line?

I'm banging my head against the desk here. At least they're only charging me for diagnostics, and not just throwing parts at it and sending me a bill. I doubt we'll have any more cold enough temps this year to do any further diagnostics on it, but that also means I've got 9 months of (hopefully) trouble-free driving ahead of me before I need to worry about it again.
From the service manual.....

Cold Weather Operation

reductant = DEF Fluid

As reductant will freeze at temperatures below 0°C (32°F), there are 2 reductant heaters. Reductant
heater 1 is in the reductant reservoir and reductant heater 2 is in the supply line to the reductant injector.
The reductant control module monitors the reductant temperature sensor located within the reservoir in
order to determine if reductant temperature is below its freeze point. If the module determines that the
reductant may be frozen, it energizes the reductant heaters.
Reductant pump operation is disabled for a calibrated amount of time to allow the heaters time to thaw
the frozen reductant. Once the thaw period expires, the module energizes the reductant pump to circulate
warm reductant back to the reservoir to speed thawing. The ECM looks for an increase in the reductant
temperature to verify that the reductant reservoir heater is working.

It could be that they are just looking for a temperature increase of "X" over a defined period of time.
 

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Discussion Starter · #3 ·
From the service manual.....

Cold Weather Operation

reductant = DEF Fluid

As reductant will freeze at temperatures below 0°C (32°F), there are 2 reductant heaters. Reductant
heater 1 is in the reductant reservoir and reductant heater 2 is in the supply line to the reductant injector.
The reductant control module monitors the reductant temperature sensor located within the reservoir in
order to determine if reductant temperature is below its freeze point. If the module determines that the
reductant may be frozen, it energizes the reductant heaters.
Reductant pump operation is disabled for a calibrated amount of time to allow the heaters time to thaw
the frozen reductant. Once the thaw period expires, the module energizes the reductant pump to circulate
warm reductant back to the reservoir to speed thawing. The ECM looks for an increase in the reductant
temperature to verify that the reductant reservoir heater is working.

It could be that they are just looking for a temperature increase of "X" over a defined period of time.
It's got to be temperature related, as the electrical aspect of the heater seems to be operating within the design parameters.

8amps for the tank (#1), 3 amps for the line (#2). 36 watts of heat just doesn't seem like it would really be enough to thaw a frozen line whilst going 70mph in single digit temperatures...

There's obviously SOMETHING wrong, as this happens literally every time it's 12° or colder, and it's not a problem for most people. But now that it's warmer, they can't seem to diagnose it, and everything checked out during the systems test.
 

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It's got to be temperature related, as the electrical aspect of the heater seems to be operating within the design parameters.

8amps for the tank (#1), 3 amps for the line (#2). 36 watts of heat just doesn't seem like it would really be enough to thaw a frozen line whilst going 70mph in single digit temperatures...

There's obviously SOMETHING wrong, as this happens literally every time it's 12° or colder, and it's not a problem for most people. But now that it's warmer, they can't seem to diagnose it, and everything checked out during the systems test.

Yep that's a lousy situation. Now to get their attention on this issue will be impossible.

I agree on the line heater versus temperature and running at highway speeds. But I haven't heard of any other people complaining about this whole issue.

The whole DEF thing in general needs to go in the trash can, such a unreliable design. I'm all for clean air but there needs to be a coherent balance between desire and reliability. The EPA really put the squeeze on the manufacturers with this requirement.
 

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Discussion Starter · #5 ·
OK so I picked up the truck this morning... Speed limiter gone, no CEL. Plugged in my scanner and it immediately showed P20BE(permanent), which they SWEAR isn't there. Told me that my scanner must be wrong because it's not GM factory diagnostic equipment. (n)
 

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Wow, first off anickode Very Nice Detailed post. Just the type of info I was looking for.
And I see that BS all over the warranty manual. As in the def delivery system is not covered under the emissions warranty. That really burns my ass. What fk is it if its not part of the emissions system. That is just plain dirty rip off there customers BS..
Reading the warranty book, there is more parts that are not covered than there is. They have added more escape routes than a trapped rat.

Keep your def tank no more than half full. Easier to defrost. It could be as simple as not enough heat to defrost the def if the tank is full before you get on the highway..
Or I think the problem is the temp sensor is not telling the computer to turn on the heaters At the right temp.
Then the NOX sensor is telling the computer the NOX levels are to high. The computer is also monitoring the def level. So it knows there is def in the tank. But NOX levels say no def getting to SCR. This will probably cause the ECU to throw a def heater code.

And it is a real issue that GM doesn’t have parts on hand to service our trucks. To many stories of people waiting weeks to get there truck back. And they will not get a part shipped in by courier even if you pay for shipping..
Dealers don’t understand why most people will not bring there vehicle in for non warranty service.
They are idiots....
 

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2019 Chevy Colorado ZR2 2.8 Duramax
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Hey! I’m new here, and I just bought a Colorado duramax. Soon after purchase I got a bunch of reductant code. Took back to the dealer, replaced a bunch of stuff, and the codes kept coming back. I seem to be lucky with the tech, as he kept looking and found a wire with a tiny abrasion on it. Inside the wire was corroded, and causing the fault.
 

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Hey! I’m new here, and I just bought a Colorado duramax. Soon after purchase I got a bunch of reductant code. Took back to the dealer, replaced a bunch of stuff, and the codes kept coming back. I seem to be lucky with the tech, as he kept looking and found a wire with a tiny abrasion on it. Inside the wire was corroded, and causing the fault.
That is spooky stuff.
where was this wire?
 

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Discussion Starter · #11 ·
Update:

Temp down to 17° last night. CEL and countdown were back on INSTANTLY upon starting my truck.

Going to a different dealership this time. They can get me in on Monday morning but have zero loaners available, which is just friggin awesome since I commute 70mi round trip every day.

This dealership has a better track record with my truck though. The one I went to before for the DEF issue also insisted that my bent turbo fin was just "normal turbo noise" and the "intake hose was loose" from me removing it to take the picture of the bent turbo fin, which I showed the technician prior to his "diagnosis".

Don't EVER go to Champion GMC Buick in Brighton MI for service. They're a bunch of scamming incompetent morons up there. I wouldn't trust those idiots to put air in my tires.
 

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My Colo is having this problem too. CEL on and off with same max speed message. Jan & Feb temps around here are often <12F.

I think it's ridiculous to blame the EPA. Nobody blamed Otto or Mr. Ford Sr. (or any early guys) when engines were hard to start in Alaska. Somebody smart made block heaters, and glow plugs, and anti-freeze, etc.

What we need is a DEF tank heater -- an externally plugin one, like what we do for engine block heaters. Can't simply put anti-gelling stuff into DEF because sensors check its quality. GM has 2 heaters, sure, but those only run AFTER engine is on. Us Snow Belt folks really need a plugin heater.

One dealer service rep recommended replacing the whole DEF assembly 🤣. It's they don't know what the simple cause is. The dealer didn't ask whether this happened in summer (it doesn't happen in warm temps). Also his fix is 🤑🤑🤑

I'm tempted to stick an electric glow rod down the DEF fill tube!! DEF is just urea and ionized water. It's not like a glow rod will combust it ... But I don't know what GM uses to make the tank. ... will do more poking around for options.

DEF freezes at 12F. Get it back up to temp and all these codes go away.
 

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Discussion Starter · #13 ·
Yes, normally it goes away when everything is thawed out... Till it doesn't. That was my issue last winter.

Many cold nights and no issues since my line was replaced.

I have pondered putting some standard rubberized plumbing heat tape on the line with a couple wraps on the tank, securing it with butyl tape, and running the cord up alongside the block heater cord. Plug both in at night, and no issues.

But it wouldn't matter. The system measures ambient temp, not DEF temp. If the ambient temp is low enough to run the def heaters, it turns them on. It detects the failure by measuring the electrical load, not the def temp. So even if your def was thawed and warm in the tank and lines, the system will call for the heater, detect the failure, and throw the code despite the def still flowing properly.
 

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Nice idea on the heat tape.

Somebody thought the DEF tank was plastic. I'll just have to freeze my butt off and look up under there.

So that 2nd dealer did end up replacing your DEF line? Not the pump, and not the wiring harness, or anything else?
 

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My Colo is having this problem too. CEL on and off with same max speed message. Jan & Feb temps around here are often <12F.

I think it's ridiculous to blame the EPA. Nobody blamed Otto or Mr. Ford Sr. (or any early guys) when engines were hard to start in Alaska. Somebody smart made block heaters, and glow plugs, and anti-freeze, etc.

What we need is a DEF tank heater -- an externally plugin one, like what we do for engine block heaters. Can't simply put anti-gelling stuff into DEF because sensors check its quality. GM has 2 heaters, sure, but those only run AFTER engine is on. Us Snow Belt folks really need a plugin heater.

One dealer service rep recommended replacing the whole DEF assembly 🤣. It's they don't know what the simple cause is. The dealer didn't ask whether this happened in summer (it doesn't happen in warm temps). Also his fix is 🤑🤑🤑

I'm tempted to stick an electric glow rod down the DEF fill tube!! DEF is just urea and ionized water. It's not like a glow rod will combust it ... But I don't know what GM uses to make the tank. ... will do more poking around for options.

DEF freezes at 12F. Get it back up to temp and all these codes go away.
I think the tank has a screen on the top of it that would prevent you from heating it from the filler. The DEF tank is made from the same polymer plastic that the fuel tank is made of. The PIC is from when I swapped my fuel tank out for a Titan but other members have said they tried to shove a small hose down the DEF filler to try to pump out the "old" fluid to do an exchange. They said the hose was stopped by a blockage and I'm just spitballing here but I would tend to think the DEf tank inlet is similar to the fuel tank as seen below.



Automotive tire Rim Gas Automotive wheel system Auto part
 

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Yes, normally it goes away when everything is thawed out... Till it doesn't. That was my issue last winter.

Many cold nights and no issues since my line was replaced.

I have pondered putting some standard rubberized plumbing heat tape on the line with a couple wraps on the tank, securing it with butyl tape, and running the cord up alongside the block heater cord. Plug both in at night, and no issues.

But it wouldn't matter. The system measures ambient temp, not DEF temp. If the ambient temp is low enough to run the def heaters, it turns them on. It detects the failure by measuring the electrical load, not the def temp. So even if your def was thawed and warm in the tank and lines, the system will call for the heater, detect the failure, and throw the code despite the def still flowing properly.
Hey Man,

I've read your post from last year several times. I' having the exact same issues w/ my '17 Colorado, to include a shitty Chevy dealership that won't listen. Did you ever get this figured out? I'm getting to the level of frustration of trading it in on an F-150 so that I have a different truck and a different dealer.

Any suggestions or lessons learned would be VERY appreciated.

Thanks.
 

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I have a P20BE code, the same symptoms as the OP, took my truck to the dealer and they were able to diagnose the issue, but I was told the part is back ordered with no ETA. Oddly they are calling the part a fuel line. My truck is a 2016 with 56,000 miles.
 

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My 2016 has been in the shop for 4 weeks waiting on the same part. Tried to check online for the part and all are on backorder as well. 84749035 is the part# they told me I needed.
 

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I got my truck back today. The dealership had it for 10 days. They had to order the part from another dealership. It’s 50 degrees today so I may not be able to tell if it’s fixed for a while. Seems the main problem was parts availability.
 
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