GM LIN Bus codes
Hello everyone first time doing anything like this so take it easy on me! Learned a ton from members on here. People that really changed my career and made me have a passion for training and learning. So I figured its time for me to give back a little bit!
2017 Silverado LTZ 6.2 Customer complaint of CEL/MIL. Running fine no issues.
Code scan brought up a U1501 and U1510 in the PCM both having to do with communication on LIN bus.
Before getting to deep I researched the codes and found a tsb for the U1510 a failing ground (g102) may cause this code and some intermittent light issues for the RF headlight. The customer did not complain of any exterior lighting issues. Checked ground anyway and it was around 50mv loaded with signal highbeams on etc. No issues there.
The ground did look quite rusted even for a 2017 but On the east coast of Canada this stuff does not last a long time. Cleaned ground anyway same result around 50mv loaded.
So moving on found the network diagram for the LIN bus. The only module connected to the PCM communicating on the bus is an Active Grille Shutter Motor Module. Ok that narrowed it down for me
Removed the trip panel over the radiator and grille. Found connector X132. Located my communication wire (GREEN/VIOLET). Hooked up my scope to see how the bus looks.
This is what I got. Looks to be a good looking waveform at first glance. But putting some training to use I know that the Lin Bus should be pulling the battery voltage to ground. It is being pulling down to about 7 volts. Knowing this is not what it should look like I disconnected the X132 connector and rechecked my bus waveform.
Looks like the bus is now looking correct and my issue lies within the module, power or ground issue or a wiring issue between x132 and the grill shutter module connector. Load tested my power and grounds both were great. A new active grille shutter was the repair for this vehicle.
Thanks everyone! diag.net/file/f5sae58k9…
Nice write up on the LIN bus. It seems more OEM'S are utilizing LIN due to low cost and very effective. Thanks for sharing!
Well-Done! Methodical and not a step skipped...I like it 👍
Nice! Thanks for sharing. I agree with you that the pattern looks good from a distance, but the details (pulled down to 7v not ground) is where its at!
Great write up with some good info.
Thanks everyone! Some things I forgot to mention I tried bi directional controls to the grille shutter with no change. Faulty Grille shutter was in the open position and the new replacement grille was normally closed.
Bidirectional test gives some extra info, but with a bad LIN bus they would not have moved the Grill anyway. You still needed to do the LIN bus tests that you did. great job. It would also be possible if the problem had been the actual LIN bus line that was short or open , the shutter might have defaulted to open anyway as a safety.
Yeah the only reason for trying the bidirectional was you can’t talk directly too the grille shutter module for any codes or data. Just making sure I was on the right track before getting deeper. Totally agree the grille May default open if there’s a bus problem! Thanks Does carquest do any training on the east coast? Feel free to email me if you’d like. …
Yes we have been doing it in Halifax, get in touch with your Carquest store.
Will do! Thanks again