Can Bus - Short Circuit
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2019 GLS 450
Can Bus - Short Circuit
I suspect a short-to-voltage issue on can bus. Scanner not communicating with multiple modules. Car running fine.
2019 GLS 450
Original Starter Battery - Napa indicates battery is good. Fully charged on NoCo 5amp maintainer. 12.4-12.6 V
Unknown condition of AUX battery (but no warning lights)
No parasite drains detected.
Car runs fine. No fault codes (but that could be lack of module communication). No warning lights. I do think the battery doesn't hold charge well (maybe loses 0.1V/night, but no parasite drain detected).
I'm using a Youcanic UCAN II C Pro OBD2 Scanner. I am not detecting all the known modules for this car. Example: "no response" on ISM, Transfer Case, Chassis Gateway, etc. Scans performed with key in position 1 (accessory), position 2 (ignition, but engine off), and with engine running.
I suspect some sort of can bus communication issue.
OBD2 check. Battery not disconnected. Door is open (but sounds like system is cycling on and off)
System OFF:
Resistance across Pins 6 and 14 - 60 ohms. [good]
Continuity between Pin 4/5 (ground) and Pin 6 - 0L open line [good, no short-to-ground]
Continuity between Pin 4/5 (ground) and Pin 14 - 0L open line [good, no short-to-ground]
Here is my problem (I think)
System Off: Voltage across Pins 4/5 and 6 (~11.5)
System Off: Voltage across Pins 4/5 and 14 (same voltage as on Pin 6)
System Off: Continuity check Pins 6 to 16 (power) - 0L open line [good, but I understanding a short-to-voltage may not run back to Pin 16]
System Off: Continuity check Pins 14 to 16 (power) - 0L open line [good, but I understanding a short-to-voltage may not run back to Pin 16]
System ON (engine not started)
Voltage across Pins 4/5 and 6 (2.5V-2.6V) [good, turned on but maybe in standby mode - not actively transmitting data] - not using an oscilloscope
Voltage across Pins 4/5 and 14 (2.4V-2.3V) [good, turned on but maybe in standby mode - not actively transmitting date] - not using an oscilloscope
System ON (engine running)
Voltage across Pins 4/5 and 6 (2.6V - can HI) [good, transmitting data] - not using an oscilloscope
Voltage across Pins 4/5 and 14 (2.4V - can LO) [good, transmitting data] - not using an oscilloscope
Questions:
1) I suspect a short-to-voltage on the Can bus Hi and Low. Is this likely correct?
2) If there is a short-to-voltage and I only get a "no response" on the scanner for modules that I know should be on the car, do I need to worry about this if the car is running fine and the system modules are working? Basically, I know tracking down a short-to-voltage can be tedious.
3) If I do need to track this short-to-voltage down, does anyone have the can bus locations for a 2019 GLS 450? I understand one or two may be behind the front passenger kick panel. I figured I'd start with disconnecting the modules at the can bus and rescan to see if I can find the faulty module pulling down all these other modules.
4) Do I just need to sit down and shut up and enjoy a good driving car?
2019 GLS 450
Original Starter Battery - Napa indicates battery is good. Fully charged on NoCo 5amp maintainer. 12.4-12.6 V
Unknown condition of AUX battery (but no warning lights)
No parasite drains detected.
Car runs fine. No fault codes (but that could be lack of module communication). No warning lights. I do think the battery doesn't hold charge well (maybe loses 0.1V/night, but no parasite drain detected).
I'm using a Youcanic UCAN II C Pro OBD2 Scanner. I am not detecting all the known modules for this car. Example: "no response" on ISM, Transfer Case, Chassis Gateway, etc. Scans performed with key in position 1 (accessory), position 2 (ignition, but engine off), and with engine running.
I suspect some sort of can bus communication issue.
OBD2 check. Battery not disconnected. Door is open (but sounds like system is cycling on and off)
System OFF:
Resistance across Pins 6 and 14 - 60 ohms. [good]
Continuity between Pin 4/5 (ground) and Pin 6 - 0L open line [good, no short-to-ground]
Continuity between Pin 4/5 (ground) and Pin 14 - 0L open line [good, no short-to-ground]
Here is my problem (I think)
System Off: Voltage across Pins 4/5 and 6 (~11.5)
System Off: Voltage across Pins 4/5 and 14 (same voltage as on Pin 6)
System Off: Continuity check Pins 6 to 16 (power) - 0L open line [good, but I understanding a short-to-voltage may not run back to Pin 16]
System Off: Continuity check Pins 14 to 16 (power) - 0L open line [good, but I understanding a short-to-voltage may not run back to Pin 16]
System ON (engine not started)
Voltage across Pins 4/5 and 6 (2.5V-2.6V) [good, turned on but maybe in standby mode - not actively transmitting data] - not using an oscilloscope
Voltage across Pins 4/5 and 14 (2.4V-2.3V) [good, turned on but maybe in standby mode - not actively transmitting date] - not using an oscilloscope
System ON (engine running)
Voltage across Pins 4/5 and 6 (2.6V - can HI) [good, transmitting data] - not using an oscilloscope
Voltage across Pins 4/5 and 14 (2.4V - can LO) [good, transmitting data] - not using an oscilloscope
Questions:
1) I suspect a short-to-voltage on the Can bus Hi and Low. Is this likely correct?
2) If there is a short-to-voltage and I only get a "no response" on the scanner for modules that I know should be on the car, do I need to worry about this if the car is running fine and the system modules are working? Basically, I know tracking down a short-to-voltage can be tedious.
3) If I do need to track this short-to-voltage down, does anyone have the can bus locations for a 2019 GLS 450? I understand one or two may be behind the front passenger kick panel. I figured I'd start with disconnecting the modules at the can bus and rescan to see if I can find the faulty module pulling down all these other modules.
4) Do I just need to sit down and shut up and enjoy a good driving car?
