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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29427
Experience:  GM Grand Master Technician 2007. 14 years experience.
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We have a 2012 Chevy express 3500 with a 6.6. Light on the

Customer Question

We have a 2012 Chevy express 3500 with a 6.6. Light on the dash says cleaning filter keep driving. Scanned vehicle found e g t sensor 4 reading 1832° removed plug from sensor and plugged into good sensor. Same reading. Tested wiring and have a good 5v
signal.
Submitted: 12 months ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 12 months ago.

Hi there, I am Cam.

I am sorry to hear about this. Can You tell me if you have any codes set?

Customer: replied 12 months ago.
No codes just the message saying cleaning filter keep diving. It goes off after driving about a half hour then will come back on when you cycle the keh
Expert:  GM Tech (Cam) replied 12 months ago.

How many miles on your Van?
During these drive cycles, how long are you driving each time?

Customer: replied 12 months ago.
I don't have the exact mileage I believe around 90k driving for about 30 min.
Expert:  GM Tech (Cam) replied 12 months ago.

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?

Customer: replied 12 months ago.
The temp never changes from 1832 and the soot load is 61
Expert:  GM Tech (Cam) replied 12 months ago.

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.

Customer: replied 11 months ago.
We performed regen and fluid quality test. The regen compleated. fluid quality test timed out. Also the dash reads 175 mile till 65mph. see owners manual. Service emission system.
Expert:  GM Tech (Cam) replied 11 months ago.

What is your VIN ? I have an idea but need to confirm your vehicle qualifies before even checking.

Customer: replied 11 months ago.
1GBZGUCL5C1159583
Expert:  GM Tech (Cam) replied 11 months ago.

Ok,does your scanner show NOX PPM for sensor 1 and sensor 2?

Customer: replied 11 months ago.
Expert:  GM Tech (Cam) replied 11 months ago.

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.

Customer: replied 11 months ago.
Both nox sensors are reading -1.0 no change while driving
Expert:  GM Tech (Cam) replied 11 months ago.

How long did you drive it? Those readings suggest they are not yet operating.

Customer: replied 11 months ago.
About 10 min I will drive it longer and let you know
Expert:  GM Tech (Cam) replied 11 months ago.

Ok, if the status shows them as allowed to operate and there is no change then It may be that both sensors are bad.

Customer: replied 11 months ago.
Ok so they came on nox 1 first reading about 200 on normal driving. Couple min later nox 2 came on reading The same. On heavy accel then coast nox 1 dropped to 18 and nox 2 drops to 30. So are both sensors bad?
Expert:  GM Tech (Cam) replied 11 months ago.

If neither dropped below 10 then they are not functioning properly.

Customer: replied 11 months ago.
How come we have no codes for this? How do we loose both at one time? And how would that affect the egt temp 4?
Expert:  GM Tech (Cam) replied 11 months ago.

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.

Customer: replied 11 months ago.
Ok installed new sensors reading correctly we have a service emissions light on dash still is there a way to clear it
Expert:  GM Tech (Cam) replied 11 months ago.

Ok, did you run another fluid quality test? Also do you have a tamper reset function?

Expert:  GM Tech (Cam) replied 11 months ago.

If it fails, see what codes set.

Customer: replied 11 months ago.
Fluid quality test passed. Do not have tamper reset function.
Expert:  GM Tech (Cam) replied 11 months ago.

Ok, what other functions do you have? The tamper reset may be required. We have that means in the dealer on our Tech 2.

Customer: replied 11 months ago.
We are using a verus
Expert:  GM Tech (Cam) replied 11 months ago.

I think that may be one you have to visit a dealer for. Is it still restricted in speed?

Customer: replied 11 months ago.
It says 157 miles till 65mph. Could we be going down the wrong path here I mean emissions is a wide range
Expert:  GM Tech (Cam) replied 11 months ago.

No Think we are on the right path. Does it pass a service regeneration still?

Customer: replied 11 months ago.
Running regen right now
Expert:  GM Tech (Cam) replied 11 months ago.

ok

Expert:  GM Tech (Cam) replied 11 months ago.

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.

Customer: replied 11 months ago.
Regan completed light is still on
Expert:  GM Tech (Cam) replied 11 months ago.

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.

Expert:  GM Tech (Cam) replied 11 months ago.

Here is the basic document I use for this.

Customer: replied 11 months ago.
Ok so I have an update. Started looking into this egt 4. Sensor. Checking voltage and resistaonce. Hooked up a tone generator to the tan wire on the sensor and lost all tone. Went up to the Ecm disconnected plug number 2 and had tone. Found that the egt 4 sensor wires actually go to plug 1. I have looked through all different parameters on this vehicle and found that this is the only one that is a definite problem...am I wrong with this will this not affect the emissions system?
Expert:  GM Tech (Cam) replied 11 months ago.

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?

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