To everyone frustrated with the availability and mystery of replacement NOx sensors:
I'm posting this to, hopefully, help with sorting out the array of part numbers for the 2015/2016 LMLs. I think this information will also work for most any model year LML if it contains one of these part numbers. Here are compatible numbers that cannot be cross-referenced anywhere that I know of. Even my local GM dealer couldn't look-up or cross reference these numbers.
Upstream Position #1 GM part numbers:
GM 19301328 (superceded, but possibly available as NOS)
GM 19302359 (GM shows this as the only replacement for 2015/16 models, NOT TRUE! This is unlikely to match your original part #, since it is a replacement for a superceded part)
GM 12662971 (if you order 19302359, this is what they send you)
GM 12648630 (this was the original part on my 2015, but no longer available)
Downstream Position #2 GM part numbers:
GM 19301329 (superceded, but possibly available as NOS)
GM 19302360 (GM shows this as the replacement for 19301329 for 2015/16 models. This is unlikely to match your original part #, since it is a replacement for a superceded part)
GM 12648631 (what my 2015 came with)
GM 12662972 (what I'm running now)
DISCLAIMER: I cannot say with 100% certainty which part number will work on every model. There are mid year variations and other part numbers out there that I have not verified. I suggest that you first check to see what part is on your LML truck (regardless of year). If your original part number is listed above, then any of the part numbers that I listed should work, so long as it is in the same position (upstream and downstream sensors are not interchangeable). IF your truck has a different part number, do some research before using any of the numbers above. Ebay has good prices on some of the above numbers. I tried to stick with GM or AC Delco parts rather than the Chinese-made ones. However, they are probably the same parts. If you pay more than $250 for a NOx sensor, you paid too much. Most of these should be between $160-250. A GM dealer will rip you off for more than $500.
NOTE: If you swap the NOx sensor yourself, it is pretty easy (unless the sensor is seized in the bung). The upstream sensor is at the rear of the engine downpipe and the controller is on the firewall (driver-side). The downstream sensor is on the top of the SCR/DPF and is much harder to access because of the driveshaft. I dropped the driveshaft, which made it much easier. After replacing the sensor you can take a scanner and clear the fault codes. If you were getting reduced speed warnings on the DIC (limp-mode), those warning will usually clear themselves after 50 miles and an overnight cool-down restart cycle (sometimes more than one cycle). If not, there may be other issues (DEF injector, DEF quality, heater, etc), If so, the fault codes will return. If you originally had several fault codes and one of those was a NOx fault code, I'd suggest starting with replacing the NOx sensor first. That may be the only issue and could be causing the other codes.
I'm posting this to, hopefully, help with sorting out the array of part numbers for the 2015/2016 LMLs. I think this information will also work for most any model year LML if it contains one of these part numbers. Here are compatible numbers that cannot be cross-referenced anywhere that I know of. Even my local GM dealer couldn't look-up or cross reference these numbers.
Upstream Position #1 GM part numbers:
GM 19301328 (superceded, but possibly available as NOS)
GM 19302359 (GM shows this as the only replacement for 2015/16 models, NOT TRUE! This is unlikely to match your original part #, since it is a replacement for a superceded part)
GM 12662971 (if you order 19302359, this is what they send you)
GM 12648630 (this was the original part on my 2015, but no longer available)
Downstream Position #2 GM part numbers:
GM 19301329 (superceded, but possibly available as NOS)
GM 19302360 (GM shows this as the replacement for 19301329 for 2015/16 models. This is unlikely to match your original part #, since it is a replacement for a superceded part)
GM 12648631 (what my 2015 came with)
GM 12662972 (what I'm running now)
DISCLAIMER: I cannot say with 100% certainty which part number will work on every model. There are mid year variations and other part numbers out there that I have not verified. I suggest that you first check to see what part is on your LML truck (regardless of year). If your original part number is listed above, then any of the part numbers that I listed should work, so long as it is in the same position (upstream and downstream sensors are not interchangeable). IF your truck has a different part number, do some research before using any of the numbers above. Ebay has good prices on some of the above numbers. I tried to stick with GM or AC Delco parts rather than the Chinese-made ones. However, they are probably the same parts. If you pay more than $250 for a NOx sensor, you paid too much. Most of these should be between $160-250. A GM dealer will rip you off for more than $500.
NOTE: If you swap the NOx sensor yourself, it is pretty easy (unless the sensor is seized in the bung). The upstream sensor is at the rear of the engine downpipe and the controller is on the firewall (driver-side). The downstream sensor is on the top of the SCR/DPF and is much harder to access because of the driveshaft. I dropped the driveshaft, which made it much easier. After replacing the sensor you can take a scanner and clear the fault codes. If you were getting reduced speed warnings on the DIC (limp-mode), those warning will usually clear themselves after 50 miles and an overnight cool-down restart cycle (sometimes more than one cycle). If not, there may be other issues (DEF injector, DEF quality, heater, etc), If so, the fault codes will return. If you originally had several fault codes and one of those was a NOx fault code, I'd suggest starting with replacing the NOx sensor first. That may be the only issue and could be causing the other codes.
