2021 GMC Yukon front radar problem
Here's a case study that I have just finished on a 2021 GMC Yukon that has had several new radar modules installed with no communications. I hope this helps.
When you say “these new GM's” referring to the key being off for programming, can you be a little more specific please? When does it start? Which vehicles?
I think what Bernie is communicating is to check service information and follow the instructions. These instructions are not exclusive to “new GM's”.
Hi Keith, as you are probably dealing with this often, could I ask what equipment you would be using for a diagnostic task like this? Is there a way to know if a module got previously programmed correctly (like a memory checksum test)?
Absolutely, the module programming event could have been verified very quickly by checking the modules calibration numbers in mode 9 (ECU Information on most tools) of any capable scan tool against the free resource posted directly on GM's ACDELCOTDS website! No scope required! I have covered this topic in depth numerus times on my website and even here possibly. I say calibration numbers…
Thanks Keith, I thought that Service/Mode 09 was for emission related modules as per EPA OBD requirements? Is that operation still referred to as Service 09 for non-emission modules?
It is not, it is usually identified a ECU information, but most techs I speak with refer to it as "mode 9 data for that module". Edited the response for clarification
Thank you, Keith, great information! I do not recall you or anyone posting this in detail here before, so I think just copying and pasting this to the main page would make a fantastic tech tip.
Absolutely correct Keith. Well said. There is no need whatsoever to waste a single moment with a scope on that diagnosis. The scan data combined with SI will lead to a rapid resolve. Just wait until someone decides to open that CAN FD bus and the SDGM shuts it down. Huh, what happened to the signal?????
Martin, what is meant by “to open CAN FD bus”? Just trying to interpret the phrase correctly.
Hi Dmitriy. Creating an open circuit on the CAN FD bus and how communication may be affected, in comparison to standard CAN.
“Creating an open circuit“ - got it. Judging from the waveform in the video the bus was shut down even without an open, just because of miscommunication between modules: diag.net/file/f4nq36rlh…
Yes Dmitriy. Because the Serial Data Authentication Confirmation (SDAC) wasn't complete or had failed, the keys were not shared with all modules, so there was no communication, as supported by DTC U1962. While the scope pics are interesting, they are not required, at least in early stage non-intrusive diagnostics for this DTC. However, I'm fairly sure that Bernie was simply curious about what…
It will tell you on SPS when it is required.
Thanks Bernie, Always learning from you & I appreciate you for posting these odd but real problems.
Hi Bernie! Nice Diag on the vehicle sir! There is a possibility that the shop may have programmed the wrong VIN into the module. This would possibly cause checksum error and the codes exhibited. Apparently there may be a problem when technicians are programming the Long Distance Radar with SPS2. They are not verifying the VIN before pushing buttons. Here is a GM reference on GM SI…
Thx Bernie.Good to see you still have passion chasing different faults around, Nice way to look into data BUS and made call based on the ACK part. Also data part of CAN bus message can tell what the message is doing even not knowing ID part.And yes was logical to be wired into a camera module since more vehicle more likely has AEB with pedestrian recognition.(At teh…