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Automotive Can Bus problem. Who knows about it?


JL Sargent
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This may or may not help: I have a 2014 GMC Sierra, and it was draining the battery. I took it to the dealership, and they couldn't find the problem, and wanted to start replacing fuse panels.The truck ran fine for a few months, and then drained a brand new battery. 

  I decide to trouble shoot it myself, having been a Master Mechanic in a previous life, and spent 24 years building trucks at GM Truck and Bus.

What I found out is the fuse block on the drivers side dash was getting wet from an unknown leak in the roof area, and the water was running down the A pillar. I simply removed the fuses and re-installed them, and it's been fine for over a year.

  There is a main fuse panel on the drivers side under the hood, plus two fuse panels inside, one on both sides of the dash, on my 2014. your '07 may be a bit different.

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On 2/26/2020 at 11:43 AM, kevinmi said:

What I found out is the fuse block on the drivers side dash was getting wet from an unknown leak in the roof area,

You might be on to something here. Maybe instead of a flaky module, I should be looking for water intrusion. Did you take any actions to stop the leak? I did notice that I had moisture on the inside of my windshield when the sun came out and was hitting it yesterday. Maybe resealing the windshield would be a good idea for me? I'm certainly going to take a bright light and try to inspect that fuse panel and the backside connections. Thanks.

 

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10 minutes ago, JL Sargent said:

You might be on to something here. Maybe instead of a flaky module, I should be looking for water intrusion. Did you take any actions to stop the leak? I did notice that I had moisture on the inside of my windshield when the sun came out and was hitting it yesterday. Maybe resealing the windshield would be a good idea for me? I'm certainly going to take a bright light and try to inspect that fuse panel and the backside connections. Thanks.

 

A bus will go down from an open or a short.  Your scenario of water creating the issue lends itself more to a wiring/connection/corrosion issue than a bad module.

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On 2/24/2020 at 1:00 PM, JL Sargent said:

No doubt about it. I'm hoping maybe somebody has seen this problem before?

 

Yeah, so what seems to be happening is that when the problem occurs, the bus goes down and I lose about everything including instrument panel, radio, On star or comm, hvac module, brake control, etc. I guess I need to locate a data junction box and add each module by splicing them in one at a time until I lose communication again. Then that would be the bad module. Sounds good anyway.

 

Look for a bad ground connection.

 

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2 hours ago, JL Sargent said:

Is it normal to have some moisture on the inside of the windshield from simply humidity and not necessarily a "leak"? 

Condensation inside the windshield doesn't necessarily indicate a leaking windshield.  It's certainly possible but if your windshield is OK, you can still have a leak somewhere.  The windshield is normally where you see condensation though.  I've seen spare tire wells in the trunk with water in them from a leaking weatherstrip create condensation on the windshield as well.

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On 2/28/2020 at 9:41 AM, JL Sargent said:

Did you take any actions to stop the leak?

I haven't tried to locate the leak yet, but I did notice that my onstar antenna on the roof has a gap in the gasket where it sits on the roof. I'll seal everything in the spring after it thaws out up here.

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For rooftop vehicles, there are typically drainage hose(s) that sometimes are routed down one or both of the  frame struts that

could on an occasion be known to fail to exit the vehicle as designed

that could introduce moisture around the windshield resulting in humidity. This same moisture could on some non-isolated designs effect the electronics associated with the operation

of vehicles.

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We did the soapy water/air pressure test on the windshield and no leaks found. I also took a bright light and looked all up under the dash and no signs of water intrusion found. We are supposed to get another big rain (4" or so) this week and if the can bus goes down,  I plan to start disconnecting modules to see if I can get communication back on the bus.

 

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Sorry  you are having this problem.

Dang hard to identify it seems.

Ground wire on a truck looked fine one time but taking it loose and wirewill brushing where attached to frame and the connector work ed in a case.

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I know the feeling, I fought one on my daughters Jeep after replacing the heater core. Mine was a no bus communication with air bag, turns out I pinched a wire when re installing the heater box.  Oddly enough it was a harness section of the can bus that really didn't have much to do with the air bag or any of the other 3 modules on that circuit.  Jeep would start and run, just no gauges.  Good luck.

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9 hours ago, The Dude said:

I know the feeling, I fought one on my daughters Jeep after replacing the heater core. Mine was a no bus communication with air bag, turns out I pinched a wire when re installing the heater box.  Oddly enough it was a harness section of the can bus that really didn't have much to do with the air bag or any of the other 3 modules on that circuit.  Jeep would start and run, just no gauges.  Good luck.

 

What kind of Jeep and how old?

JJK

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