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Discussion Starter #1
Had this pop up on me on the way home from work yesterday. Able to get home and its showing 20 miles before my first reduction. 2014 with 142k miles. It has had the Nox and DEF tank recall done last year. I took this car over from my wife about a month ago when I bought her a 4 Runner. Her commute is about 30 mins of interstate each day. Mine is over an hour each way running 70-75 mph for at least an hour of that, for what that info is worth. Most of the miles on this car is running at interstate speeds, not a lot of stop and go use.

Is there anyway for me to reset this fault? I have an OBS cable for a my laptop, Im able to clear the CEL but not showing any way to clear this fault.

So I've read over all the post I could find on here and other places about this issue. So far it doesn't seem like there is a good explanation on how to resolve this issue. Best I've found so far is it caused by a difference or problem between the Nox 1 and Nox 2 sensor. Im showing them between 150-200 each online. I hate to throw $400 at a maybe... The other resolutions I've seen are people running the car at WOT for a time to try an burn/clear out any soot in the system, after adding or replacing the DEF fluid. I ran my cruze at around 3k RPMs for about 15-20 mins last night on the way home after getting this fault. Added more DEF fluid at the house (it was low) and did the same for another 10 mins or so with no change. I cant bring myself to floor the car in hopes it "might" fix the issue, my luck I'll do nothing but blow up the engine. So I'm not sure what to do from here. Everything is out of warranty, so if I take it to the dealership I know Ill get hit with $1k or more in repairs, my local dealership seem like good people but all dealerships are way overpriced for repairs. I could pull the DEF tank, flush and add more fresh fluid, shouldn't be to hard to do. I could go ahead and drop the $1500 for a delete and tune, would that clear up this issue? Seems like it would being is takes are of all the parts causing this issue, but I'm not seeing the delete/tune kits online any longer.

Any advice would be appreciated
 

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Not sure about how best to clear the code, it may require a visit to the dealer.

Delete will definitely re-program/clear codes if you’re lucky enough to find one still available.
 

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Discussion Starter #3
I'm going to check it again when I get home, run it down the road and see what happens. If that doesn't do anything I'm thinking about disconnecting the battery over night and see if that does anything.
 

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Are there any OBD codes appearing beyond the Poor DEF Quality message? If so, what were the fault codes? If you have codes, they will help narrow the source of the problem. If you have the DEF message, but no codes, you're probably looking at a clogged or failed DEF injector, or a NOX2 sensor that is giving a bad reading, but hasn't completely died to set the NOX2 code.

It's almost never an actual problem with the DEF itself, especially if you have since topped off with fresh. A lack of DEF entering the system due to a clogged or failed injector will cause the same kind of NOX sensor readings that bad DEF would cause, though, so it can set off the Poor DEF Quality message.

If you have stock emissions, then there is no particulate matter making it back to the NOX2 sensor to clog it up, and if you're getting a poor DEF message from a NOX sensor issue, it's almost always NOX2 and not NOX1 causing it. So, doing the Italian Tune Up method isn't going to genuinely do anything to burn off anything on that sensor. In my experience, sometimes the Poor DEF Quality message will appear intermittently before it eventually sets permanently. So, I think people clearing the DEF message with running the engine hard are just experiencing a coincidence, and it will return, whether it takes a week and a couple hundred miles, or a few months and 10,000 miles, as the underlying fault becomes more consistent.
 

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Discussion Starter #5
Are there any OBD codes appearing beyond the Poor DEF Quality message? If so, what were the fault codes? If you have codes, they will help narrow the source of the problem. If you have the DEF message, but no codes, you're probably looking at a clogged or failed DEF injector, or a NOX2 sensor that is giving a bad reading, but hasn't completely died to set the NOX2 code.

It's almost never an actual problem with the DEF itself, especially if you have since topped off with fresh. A lack of DEF entering the system due to a clogged or failed injector will cause the same kind of NOX sensor readings that bad DEF would cause, though, so it can set off the Poor DEF Quality message.

If you have stock emissions, then there is no particulate matter making it back to the NOX2 sensor to clog it up, and if you're getting a poor DEF message from a NOX sensor issue, it's almost always NOX2 and not NOX1 causing it. So, doing the Italian Tune Up method isn't going to genuinely do anything to burn off anything on that sensor. In my experience, sometimes the Poor DEF Quality message will appear intermittently before it eventually sets permanently. So, I think people clearing the DEF message with running the engine hard are just experiencing a coincidence, and it will return, whether it takes a week and a couple hundred miles, or a few months and 10,000 miles, as the underlying fault becomes more consistent.
Took it for a drive today to pick up my daughter and no change. It hit the 100 miles so now Im reduced to 65mph. It has had a P20E4 code for awhile. I changed an O2 sensor for this code (the up stream sensor near the top) and it will go away for a while then come back. Today it is showing a new code that I've never seen. P0420. When this problem first started a few days ago I checked the codes and cleared them trying to reset this fault and the P20E4 was the only code listed. Today on the way home the CEL came back on and it is showing both these codes. So maybe its the same O2 sensor again? Maybe the one I replaced it with was bad?
 

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your fluid isnt bad, dont waste time changing it/flushing it

you dont need WOT to burn/regen, one gear down is plenty

if you get @Snipesy app youll be able to do a manual regen ---biscan in your app store, but this isnt your issue

you can change the sensor yourself, im unsure whether it needs the gm computer or not to reset it
 

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Took it for a drive today to pick up my daughter and no change. It hit the 100 miles so now Im reduced to 65mph. It has had a P20E4 code for awhile. I changed an O2 sensor for this code (the up stream sensor near the top) and it will go away for a while then come back. Today it is showing a new code that I've never seen. P0420. When this problem first started a few days ago I checked the codes and cleared them trying to reset this fault and the P20E4 was the only code listed. Today on the way home the CEL came back on and it is showing both these codes. So maybe its the same O2 sensor again? Maybe the one I replaced it with was bad?
P20E4 is Exhaust Gas Temperature Sensor 2/3 correlation (so nothing to do with your O2 or NOX sensors). The good news is they're way cheaper than NOX sensors and a really easy change. You can pull up EGT sensor values in the torque app or with bi-scan. Sensors 1 and 2 should be very close, with 2 being slightly lower 80% of the time. Sensor 3 should be noticeably lower than the others, but could be nearly as hot as the others if you've been running hard or in a re-gen. The one with a wonky reading (way too high or low, or pegged out a minimum or maximum, or stuck at a round number like 1200.00) will be the one that needs to be replaced. Since they're only $30-40 each, you could even throw both sensors at it if you don't have a way to scan them, or if you just want to go all-in on ruling them out. EGT2 is mid-low DPF, and EGT3 is under the car by the DEF injector.

P0420 is a code I run across all the time on gas vehicles, but never on my Diesel. On gassers, it means the catalytic converter is not working at the specified standard. I'm not sure if it is meant to reference the "Diesel Oxidation Catalyist" (top portion of our DPF unit) or the SCR (the unit where the DEF does its magic) on our cars, since both sometimes get referred to as catalytic converters at times, and "catalyst efficiency below threshold" doesn't help narrow it down. Since you have the DEF quality message set, my guess is it's related to the SCR in this instance.

Step 1 is going to be dealing with those EGT sensor(s). Since SCR does rely on input from EGT for operation, it's possible that it is metering incorrectly or becoming disabled due to the bad EGT sensor. If you're lucky, getting your EGT readings back in spec will make everything else fall into place. If not, at least you've cleared that code, and you can focus on why the SCR is not doing its job, thus setting the DEF quality message. EGT sensors do not require a computer reset like the NOX sensors (sometimes) do to clear the OBD code. If the EGT sensor fixes things, the DEFmessage will clear on its own. If the DEF message doesn't clear, then I'd go to the DEF injector next.
 

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Discussion Starter #9
P20E4 is Exhaust Gas Temperature Sensor 2/3 correlation (so nothing to do with your O2 or NOX sensors). The good news is they're way cheaper than NOX sensors and a really easy change. You can pull up EGT sensor values in the torque app or with bi-scan. Sensors 1 and 2 should be very close, with 2 being slightly lower 80% of the time. Sensor 3 should be noticeably lower than the others, but could be nearly as hot as the others if you've been running hard or in a re-gen. The one with a wonky reading (way too high or low, or pegged out a minimum or maximum, or stuck at a round number like 1200.00) will be the one that needs to be replaced. Since they're only $30-40 each, you could even throw both sensors at it if you don't have a way to scan them, or if you just want to go all-in on ruling them out. EGT2 is mid-low DPF, and EGT3 is under the car by the DEF injector.

P0420 is a code I run across all the time on gas vehicles, but never on my Diesel. On gassers, it means the catalytic converter is not working at the specified standard. I'm not sure if it is meant to reference the "Diesel Oxidation Catalyist" (top portion of our DPF unit) or the SCR (the unit where the DEF does its magic) on our cars, since both sometimes get referred to as catalytic converters at times, and "catalyst efficiency below threshold" doesn't help narrow it down. Since you have the DEF quality message set, my guess is it's related to the SCR in this instance.

Step 1 is going to be dealing with those EGT sensor(s). Since SCR does rely on input from EGT for operation, it's possible that it is metering incorrectly or becoming disabled due to the bad EGT sensor. If you're lucky, getting your EGT readings back in spec will make everything else fall into place. If not, at least you've cleared that code, and you can focus on why the SCR is not doing its job, thus setting the DEF quality message. EGT sensors do not require a computer reset like the NOX sensors (sometimes) do to clear the OBD code. If the EGT sensor fixes things, the DEFmessage will clear on its own. If the DEF message doesn't clear, then I'd go to the DEF injector next.

Well, I had a big long post with tons of questions about everything and you posted this. So this will be my first step, It will be later this afternoon before I can check these out with the scan gauge but I will look and see what I can find. I may just order both sensors and swap them out when I have time Monday or Tuesday. I swapped the EGT 1 sensor about 6 months ago and the code went away for awhile, then would come back and go away again.
 

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Discussion Starter #10
Just ordered the EGT#2 (55581034) and #3 (555810345) sensors. I replaced the #1 this summer when first started getting the P20E4 code. Figured might as well replace the other two and have all three be new parts. Amazon will have them here on Monday. Rock auto was cheaper but would be almost two weeks out. My local O'reillys could have them today but they are almost twice the price. I was unable to check the readings for the sensors and will not have time to do it until Monday. I will keep this post updated with what I find, thanks again for all the help and info. I hope this does the trick.
 

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P20E4 is Exhaust Gas Temperature Sensor 2/3 correlation (so nothing to do with your O2 or NOX sensors). The good news is they're way cheaper than NOX sensors and a really easy change. You can pull up EGT sensor values in the torque app or with bi-scan. Sensors 1 and 2 should be very close, with 2 being slightly lower 80% of the time. Sensor 3 should be noticeably lower than the others, but could be nearly as hot as the others if you've been running hard or in a re-gen. The one with a wonky reading (way too high or low, or pegged out a minimum or maximum, or stuck at a round number like 1200.00) will be the one that needs to be replaced. Since they're only $30-40 each, you could even throw both sensors at it if you don't have a way to scan them, or if you just want to go all-in on ruling them out. EGT2 is mid-low DPF, and EGT3 is under the car by the DEF injector.

P0420 is a code I run across all the time on gas vehicles, but never on my Diesel. On gassers, it means the catalytic converter is not working at the specified standard. I'm not sure if it is meant to reference the "Diesel Oxidation Catalyist" (top portion of our DPF unit) or the SCR (the unit where the DEF does its magic) on our cars, since both sometimes get referred to as catalytic converters at times, and "catalyst efficiency below threshold" doesn't help narrow it down. Since you have the DEF quality message set, my guess is it's related to the SCR in this instance.

Step 1 is going to be dealing with those EGT sensor(s). Since SCR does rely on input from EGT for operation, it's possible that it is metering incorrectly or becoming disabled due to the bad EGT sensor. If you're lucky, getting your EGT readings back in spec will make everything else fall into place. If not, at least you've cleared that code, and you can focus on why the SCR is not doing its job, thus setting the DEF quality message. EGT sensors do not require a computer reset like the NOX sensors (sometimes) do to clear the OBD code. If the EGT sensor fixes things, the DEFmessage will clear on its own. If the DEF message doesn't clear, then I'd go to the DEF injector next.

Wow. This is awesome info.
 

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Discussion Starter #12
Edit: I Swapped the EGT#2 eairler this summer when trying to fix the P20E4, not the #1. My Mistake

So today I swapped the EGT# 2&3 sensors (#2 again), cleared the codes. Drove about 40 miles with 4 or so engine shutdown and restarts an no change as far as the Exhaust Fluid problem, but the P20E4 did not come back but it is still listed as a permanent code. My understanding is that it takes awhile for a permanent code to clear itself out. Tomorrow Im thinking about pulling and trying to clean the NOX# 1 & 2 and see if that changes anything. Not sure if thats a good ideal or not? Only other thing that has been suggested is the DEF injector. Im not sure how to check it, or where its at. I think i read somewhere its near the EGT#3.

So for anyone that has had this issue before, When you made a repair, how long of driveing did it take before the Exhaust Fluid Poor fault cleared itself? Maybe 40 miles of driving isnt enough? Maybe the EGT sensor problem is not related to the Exhaust fluid fault?

If the EGTs are not going to resolve this issue, (I dont think they will because it would be to easy, and nothing in my life is easy) then the DEF Injector Im guessing is next. Im doing some searching next for any info on its location and how to remove/clean it.

Im due for an Oil change at the dealer, I wonder if they can force a manual regen if that would have any affect on this issue.
 

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Update on whats going on.

Info from another forum pointed me to the DEF reservoir heater assembly. Also found a page talking about the heater failures and that it would cause my issue. That page is here. So I ordered the assembly, and was able to swap it out earlier today. Put about 40 miles or so on it and no change. I'm now at about 50 miles before I'm reduced to 4mph max. I have had any other codes or CEL since I swapped the EGT#2 & #3 sensors. Kind of lost on where to go from here. All the other parts I'm trying to research all show that I would have a CEL and codes if they were causing any issues.
 

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Update on whats going on.

Info from another forum pointed me to the DEF reservoir heater assembly. Also found a page talking about the heater failures and that it would cause my issue. That page is here. So I ordered the assembly, and was able to swap it out earlier today. Put about 40 miles or so on it and no change. I'm now at about 50 miles before I'm reduced to 4mph max. I have had any other codes or CEL since I swapped the EGT#2 & #3 sensors. Kind of lost on where to go from here. All the other parts I'm trying to research all show that I would have a CEL and codes if they were causing any issues.
Per your link "Once the heater is replaced the vehicle will need to be driven up to 100 miles for the code to clear from the system "
 

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Per your link "Once the heater is replaced the vehicle will need to be driven up to 100 miles for the code to clear from the system "
I did read that, I found another post stating that it should do it in 20-40 miles. I'm unable to find that post at this time. I thought I had it bookmarked at home but I guess its on my work PC. Anyway, Any idea what would cause it to take "up to 100 miles" before the fault with reset? With a fault that is already limiting the drivability of the vehicle seems strange that you would have to drive such a long distance after a repair in order to clear the fault. I wonder if it needs road miles or just run time?
 

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I did read that, I found another post stating that it should do it in 20-40 miles. I'm unable to find that post at this time. I thought I had it bookmarked at home but I guess its on my work PC. Anyway, Any idea what would cause it to take "up to 100 miles" before the fault with reset? With a fault that is already limiting the drivability of the vehicle seems strange that you would have to drive such a long distance after a repair in order to clear the fault. I wonder if it needs road miles or just run time?
I'm not sure about what circumstances require the 20-40 or 100 mile drive to reset, but both times I've replaced a reservoir, the code has cleared on the next engine start with no drive time at all.
 

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P0420 comes up with:

Diagnostic Instructions
DTC Descriptor
DTC P0420
Catalyst System Low Efficiency
Circuit/System Description

The diesel oxidation catalyst (DOC), main function is to control emissions of non methane hydrocarbons and particulate (soot). Its secondary function is to assist with the diesel particulate filter (DPF) regeneration, by obtaining and sustaining the temperature necessary for regeneration. In order to generate the high exhaust temperatures needed for regeneration, the aftertreatment system increases exhaust temperatures by injecting diesel fuel into the exhaust system via post-injection. The injected fuel is converted into heat by the DOC to incinerate soot accumulated in the DPF. The engine control module (ECM) monitors the exhaust gas temperature sensor 1 and 2 to determine if the operating temperature of the catalyst is achieved during a cold-start catalyst warm-up.


The hydrocarbon conversion to oxygen is calculated from the heat flow in the oxidation catalyst, based on measured and modeled temperatures, to determine the efficiency of the oxidation catalyst. The modeled temperatures are calculated using the injection quantity and air mass flow. When the ECM detects that the diesel oxidation catalyst hydrocarbon conversion rate is below a calibrated threshold during a cold-start catalyst warm-up phase, this DTC sets.
Conditions for Running the DTC

  • DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P011B, P0234, P0299, P0545, P0546, P1400, P2032, P2033, P20E2, P2199 or P2463 are not set.
  • Battery voltage is greater than 11 V.
  • Engine run time is greater than 10 s.
  • Ambient air temperature is greater than −7°C (19.4°F).
  • Coolant temperature at startup is between −7°C and 36°C (19.4°F and 97°F).
  • Barometric pressure (BARO) is greater than 74.8 kPa (10.8 psi).
  • Hydrocarbon mass flow into the DOC is greater than 0.0225 g/s.
  • The ECM is commanding a cold-start catalyst warm-up.
  • DTC P0420 runs once per driving cycle when the above conditions are met.
Conditions for Setting the DTC

The ECM determines that the efficiency of the diesel oxidation catalyst has degraded below a calibrated threshold.
Action Taken When the DTC Sets

DTC P0420 is a Type B DTC.
Conditions for Clearing the DTC

DTC P0420 is a Type B DTC.
Diagnostic Aids

The use of off road red dye fuel or continuing use of non ultra low sulfur fuel may be a contributor to diesel oxidation catalyst failure.
Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference


Component Connector End Views

Component View Reference


Powertrain Component Views

Description and Operation


Exhaust Aftertreatment System Description

Electrical Information Reference

DTC Type Reference


Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference


Control Module References for scan tool information
Circuit/System Verification

  1. Ignition On.
  2. Verify DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P011B, P0234, P0299, P0545, P0546, P1400, P2032, P2033, P20E2, P2199 or P2463 are not set.
    • If no DTC is set

  3. Engine running, observe the DTC information with a scan tool. DTC P0420 should not be set.
    • If the DTC is set
      Refer to Circuit/System Testing.
    • If the DTC is not set

  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
  5. Verify the DTC does not set.
    • If the DTC sets
      Refer to Circuit/System Testing.
    • If the DTC does not set

  6. All OK.
Circuit/System Testing

  1. Verify the following conditions do not exist with the air induction system and exhaust system:
    • Induction system leaks — Refer to Induction System Smoke Test in Charge Air Cooler Diagnosis.
    • Exhaust leaks before or after the diesel oxidation catalyst. Refer to Exhaust Leakage for further diagnosis.
    • Physical damage.
    • Loose or missing hardware.
    • If a condition is found
      Repair or replace the affected exhaust system components as necessary.
    • If no condition is found

  2. Verify the following conditions do not exist with the diesel oxidation catalyst:
    • Physical damage or alterations.
    • Internal rattles caused by a damaged catalyst substrate.
    • Restrictions.
    • If a condition is found
      Replace the diesel oxidation catalyst.
    • If no condition is found

  3. Observe the scan tool Freeze Frame/Failure Records data for DTC P0420. Determine the temperature difference between EGT Sensor 1 and 2 and EGT Sensor 2 and 3.
    • If EGT Sensor 3 is greater than EGT Sensor 2 by at least 100°C (180° F) and EGT Sensor 2 is within 100°C (180° F) of EGT Sensor 1
      Replace the diesel oxidation catalyst.
    • If EGT Sensor 3 is not greater than EGT Sensor 2 by at least 100°C (180° F) and EGT Sensor 2 is at least 100°C (180° F) greater than EGT Sensor 1

  4. Verify the following conditions do not exist:
    • Off road fuel or red dye fuel.
    • Low quality B20 fuel.
    • Fuel containing high sulfur content.
    • Engine oil or coolant consumption.
    • If a condition is found
      Repair as necessary.
    • If no condition is found

  5. If all components test normal and no conditions are found, operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
    • If the DTC sets
      Refer to Circuit/System Testing – step 1
    • If the DTC does not set

  6. All OK.
Repair Instructions

Seems like it could be possible for your egt sensors to give you a false P0420.

I can't find anything that talks about mileage with regards to the DEF Quality Poor message but I did see this:

Repair Verification

  1. Install any components or connectors that have been removed or replaced during diagnosis.
  2. Perform the scan tool NOx Sensor 1 or 2 Reset procedure after replacing the NOx sensor 1 or 2
  3. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
  4. Clear the DTCs.
  5. Ignition Off, all vehicle systems Off, this may take up to 2 minutes.

  6. Note: The diesel exhaust fluid must be greater than −7°C (+19°F) and not in frozen tank status before proceeding with this procedure.
  7. Ignition On.
  8. Verify there are no leaks in the system when commanding the Reductant System Leak Test On with a scan tool.
    • If a leak is found
      Repair as necessary
    • If no leak is found

  9. Warning: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
  10. In order to clear the Exhaust Fluid Quality warning message, if illuminated, drive the vehicle 30 minutes.
    • If the message does not clear
      A condition with the system still exists.
    • If the message clears

  11. All OK.
 

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Discussion Starter #18
P0420 comes up with:


Seems like it could be possible for your egt sensors to give you a false P0420.

I can't find anything that talks about mileage with regards to the DEF Quality Poor message but I did see this:

seems like some good info. I've done all I think I can do to it short of swapping the Nox sensors. Everything I've read said if there was an issue with one of those there are several codes I should get. But, watching the Nox1 and 2 readings, the Nox 1 was all over there place. Anywhere from 20.0 up to 400.0 depending on the engine RPMs. Im not sure if thats normal or not. The Nox 2 stayed at 99.00 and never moved. I had my tool set to Nox Bank 1 senor 1 and sensor 2. I could swap the Nox sensors but best prices I could find are about $200 each. Im to the point I need to get it back running so I dropped it off at the dealer at Christmas. From everything I've done and test driving to see if its repaired I had about 20 miles left before Im limited to a max speed of 4mph. They said it would be some time after the first before they could look at is so as soon as I get an update on the cause of the issue I will let yall know.
 

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If NOx2 stays at 99 when NOx1 is below 99, something sounds fishy.
The fact that NOx2 is totally unresponsive would lead me to guess that NOx2 sensor or wiring is faulty, but betting $200 on a guess can be a hard bet for some to make.

OTOH, Paying $100ish for diagnosis and then probably paying dealer price for NOx2 plus install might make the $200 gamble more palatable.
 

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seems like some good info. I've done all I think I can do to it short of swapping the Nox sensors. Everything I've read said if there was an issue with one of those there are several codes I should get. But, watching the Nox1 and 2 readings, the Nox 1 was all over there place. Anywhere from 20.0 up to 400.0 depending on the engine RPMs. Im not sure if thats normal or not. The Nox 2 stayed at 99.00 and never moved. I had my tool set to Nox Bank 1 senor 1 and sensor 2. I could swap the Nox sensors but best prices I could find are about $200 each. Im to the point I need to get it back running so I dropped it off at the dealer at Christmas. From everything I've done and test driving to see if its repaired I had about 20 miles left before Im limited to a max speed of 4mph. They said it would be some time after the first before they could look at is so as soon as I get an update on the cause of the issue I will let yall know.
Based on those readings, either NOX2 or something involved with getting the DEF into the system (lines, injector, etc.) are the problem. NOX1 should vary with engine load/speed/temp. NOX2 should be steady, but 99 seems high. (Unfortunately, I'm no longer able to give a reference value from my own vehicle on what a proper NOX2 reading should be.) If I can remember correctly when I did look at those values long ago, it seems like NOX2 should be at or near zero if the SCR is working properly. Will be interesting to see what the dealer comes back with and if they're successful.
 
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