Lost communication to canbus

[Stormtroopin]

Went to start my truck after work yesterday and on first attempt just heard a click, attempted agian and truck fired right up. This morning I went to start it with the fob and agian didn’t start, jumped in and hit the start button and truck fired up but had check engine light. Got to work and scanned it with a couple codes saying lost communication to can bus,see owner’s manual. Wondering what the issue might be, any suggestions or tips would be greatly appreciated.

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[Hootbro]

Without putting a scope on the can bus signal and start to wiggle wires to and from the PCM, pretty much anything is a stabbing guess.

The green Star Can Buss Junction behind the glove box is a somewhat known failure point but that is usually when multiple system anomalies start to cascade and pile up.

 

[Mr._Bill]

How old are the batteries?

 

[Stormtroopin]

Aux is original, gana start there. I replaced the main less than a year ago.

 

[Mr._Bill]

Aux is original, gana start there. I replaced the main less than a year ago.

Batteries should both be replaced at the same time. I would start with a new Aux Battery, fully charge both of them, and reset the IBS. Low voltage can cause all kinds of odd issues.

 

[ShadowsPapa]

Went to start my truck after work yesterday and on first attempt just heard a click, attempted agian and truck fired right up. This morning I went to start it with the fob and agian didn’t start, jumped in and hit the start button and truck fired up but had check engine light. Got to work and scanned it with a couple codes saying lost communication to can bus,see owner’s manual. Wondering what the issue might be, any suggestions or tips would be greatly appreciated.

I'd pull the glove box out and reseat all of the connectors in that green star connector. It sure made a difference with mine 2 or 3 years ago.

Without the exact codes you got, hard to say.

You can check the battery voltage with the truck at rest but unless it's below 12.0 my thoughts are against that.

 

[swtrailboss]

My truck did the same thing when the Aux crapped out. The PO replaced only the main and it would take two taps on the start button to get her to wake up. Amazon has (had?)a good price on the battery you need. AC delco gold AUX 14-200….. as Mr Bill says—make sure you fully charge this battery before installing!!!!! Don’t skip this step.

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