All- Looking to get some clarity on a CAN issue I have been chasing.
Vehicle- 2021 Chevy Tahoe
The original issue with the car was no-start condition. After pressing the start/stop button the vehicle would do nothing. After about 5 seconds, I would get a 'press start again.' The car would typically throw a ton of codes once it finally started. More often than not, the trans would also go into reduced acceleration / limp mode.
Another big item to note is that the check engine light would sometimes flicker at a failed start. The flicker is not like something i've seen before, it looks like a short pulse flicker, not the typical 'misfire alarm' flicker.
This lead me down a wild goose chase of checking every single connector from the engine bay, in the cabin, and to the rear of the car. After finding nothing obvious from connectors or grounds, I started shooting the CAN segments for a bad loop.
Everything checked out EXCEPT CAN 5.
I checked resistance at the X211 connector and had a 120 Ohm reading, meaning one of the branches was bad. I disconnected the connector and checked both ways. The branch to the radio came back at 120 Ohms, meaning it is good. The opposite branch kicked back at 4 Ohms, meaning there is an issue. I have the very base model, which means the CAN branch on this side ends at the 'heater and air conditioning auxiliary control' module.
Once I unplugged the module, the car has had ZERO issues. I do have one code, but its for the unplugged CAN channel. However the car starts up without issue every time.
I decided to buy a new heater and air conditioning aux control module and swap it out with a new one. Once I did that, the car ran fine for about 1 day, then the exact same issues came back. I went to check the same pins, and had a 4 Ohms reading again. I am stupid and never checked the new part when it came in, wondering if it was bad from the factory?
I also checked each wire leading to the module to make sure it was not hitting ground, and found OL on each end.
This leads me to my question:
The CAN wires are on Pin 12 and 13. When I hit the back of the module with a meter, I get back around 4 Ohms...This means its short and bad right?
What is weird, is I hit pins 15 and 15, and they come back at 120 Ohms...but none of those pins have connectors back to the car on the male plug. CAN 5 schematic is attached for reference.
I am thinking of buying another module and testing it when it comes in, but also I am starting to think I am going down the wrong troubleshooting path?
Any advice/ feedback is appreciated.
Vehicle- 2021 Chevy Tahoe
The original issue with the car was no-start condition. After pressing the start/stop button the vehicle would do nothing. After about 5 seconds, I would get a 'press start again.' The car would typically throw a ton of codes once it finally started. More often than not, the trans would also go into reduced acceleration / limp mode.
Another big item to note is that the check engine light would sometimes flicker at a failed start. The flicker is not like something i've seen before, it looks like a short pulse flicker, not the typical 'misfire alarm' flicker.
This lead me down a wild goose chase of checking every single connector from the engine bay, in the cabin, and to the rear of the car. After finding nothing obvious from connectors or grounds, I started shooting the CAN segments for a bad loop.
Everything checked out EXCEPT CAN 5.
I checked resistance at the X211 connector and had a 120 Ohm reading, meaning one of the branches was bad. I disconnected the connector and checked both ways. The branch to the radio came back at 120 Ohms, meaning it is good. The opposite branch kicked back at 4 Ohms, meaning there is an issue. I have the very base model, which means the CAN branch on this side ends at the 'heater and air conditioning auxiliary control' module.
Once I unplugged the module, the car has had ZERO issues. I do have one code, but its for the unplugged CAN channel. However the car starts up without issue every time.
I decided to buy a new heater and air conditioning aux control module and swap it out with a new one. Once I did that, the car ran fine for about 1 day, then the exact same issues came back. I went to check the same pins, and had a 4 Ohms reading again. I am stupid and never checked the new part when it came in, wondering if it was bad from the factory?
I also checked each wire leading to the module to make sure it was not hitting ground, and found OL on each end.
This leads me to my question:
The CAN wires are on Pin 12 and 13. When I hit the back of the module with a meter, I get back around 4 Ohms...This means its short and bad right?
What is weird, is I hit pins 15 and 15, and they come back at 120 Ohms...but none of those pins have connectors back to the car on the male plug. CAN 5 schematic is attached for reference.
I am thinking of buying another module and testing it when it comes in, but also I am starting to think I am going down the wrong troubleshooting path?
Any advice/ feedback is appreciated.
