Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hi there, I am Cam.
I am sorry to hear about this. Can You tell me if you have any codes set?
How many miles on your Van? During these drive cycles, how long are you driving each time?
OK that is strange. Without a code set, it makes me wonder if the system is still seeing soot in the system or a pressure difference over the filter. Had you done any repairs prior to this? With your EGT 4, did you say it still showed that temperature after it as unplugged?What is the resistance over it?
OK this could be wiring then or even the ECM. DO you have the means to diagnose this issue?
Attached is the code chart for EGT issues, an ECM pinout and schematic.
What is your VIN ? I have an idea but need to confirm your vehicle qualifies before even checking.
Ok,does your scanner show NOX PPM for sensor 1 and sensor 2?
Ok what I want you to do is drive it for a little bit, 5 mins should be enough. While under normal driving, not heavy accel, see what the NOX 1 and Nox 2 reading is. Ideally Nox 2 should be more than 70% less than NOX 1. Also then while driving do a hard accel then let off and allow the van to coast with 0 throttle. See if the NOX sensors in both 1 and 2 show under 10 ppm. IF not, replace the one that does not. I suspect you will need to replace NOX 2, better yet I thin you are still under engine warranty so gM may pay for it.
How long did you drive it? Those readings suggest they are not yet operating.
Ok, if the status shows them as allowed to operate and there is no change then It may be that both sensors are bad.
If neither dropped below 10 then they are not functioning properly.
The reading is not outside of the expected range and that why it would not set codes. I am not sure how it impacts EGT 4, that is normally not a problem. Let me send you the document I have that outlines these readings.
Ok, did you run another fluid quality test? Also do you have a tamper reset function?
If it fails, see what codes set.
Ok, what other functions do you have? The tamper reset may be required. We have that means in the dealer on our Tech 2.
I think that may be one you have to visit a dealer for. Is it still restricted in speed?
No Think we are on the right path. Does it pass a service regeneration still?
So far you are doing great. These emissions systems when they give trouble are truly a pain to clear. Finding the exact issue and often without codes makes it even worse. The fact it passed the fluid test is a really good sign. That’s the one I often have troubles getting past and the last couple required the DOC to be replaced.
Ok so the last step is to get the tamper system reset. If your will not do that then you need to go to the dealer to have it done. Should take about 5 mins. That is the last step to this. Otherwise the regen and fluid test would have failed.
Here is the basic document I use for this.
This will, but its odd that it does not set codes for it. The tan wire is the ground wire for the sensor. IF you splice that tan to ground, does it read correctly then?