2017 2.8 Duramax in limp with no engine code.
Hi, I've been driving my first diesel for 15,000 mi over 4 months and I'm already frustrated. I have a 2017 Chevy Colorado with the 2.8 Duramax. A week ago it threw a check engine code with a flashing DEF light and a message on the dash that reads "DEF fluid quality poor." I use premium, DEF fluid and always keep my DEF in the "OK" range.the moment I notice it drop to 30% I refill.
After a quick scan, codes for NOX sensors position 1 and particulate matter sensor came up. I work in a shop and change sensors all the time. however, I'm new to diesel and I love the truck so far so I didn't want to risk pulling the sensors myself. I took it to the dealership and after diagnostics I was quoted 3K to change out the DEF injector, particulate matter sensor and nox sensor 1.
the technician told me that the def injector head was cracked and was more than likely shorting nox sensor 1. 3k seemed very steep for the replacement of an injector and two sensors but I wanted to err on the side of caution so I gave the okay for the repair, hoping that a technician more experienced than myself would make the right call.
After replacing the injector head and both sensors, the check engine light code disappeared. however, the vehicle is still in limp. The dealership told me that the EGR temperature sensor needed to be replaced next and quoted me another $700. They informed me that after replacing the sensors and performing a reductant system bay test after regeneration a new code came up P040B. frustrated and without my truck for a week I paid them. brought it home and decided to take a look at the EGR sensor and valve myself. After pulling the sensor I realized it was covered in soot so I cleaned it off. After reinsertion of the sensor and reconnecting the battery, I started the truck up and scanned for codes. No check engine codes but the truck was still in limp mode and the only code that was showing was for the PMS sensor which I paid them to replace and troubleshoot. There was no mention of the PMS code when I picked up my truck and I still cannot find the P040b code that they insisted set after the bay test and regen.
Tomorrow morning I plan on pulling the entire valve in a last stitch effort to manually clean it before taking it to The dealer I that I bought it from which agreed to replace egr sensor and diagnose for free. I'd greatly appreciate any and all advice on how to to troubleshoot and fix myself before I spend any more money that I don't have.