Rear Window Defroster

[Petey]

Now that is turned cold again I just found out my rear defroster is inop.

Is there an easy way to access the main liftgate electrical connector? I popped the rubber boot off the top but I didn't see it. Do you have to pull the headliner down or pop the plastic trim off the gate?

What I know so far.

Both tabs are attached.
The scanner is telling me the liftgate module is seeing the command to turn on.
Liftgate module is seeing 14v at the defroster relay
there is a rear grid circuit code (sometimes history, others current) when I delete it it does not come right back.
Not getting 12v when I touch the left and right tab with a MM
I am getting continuity to ground when I touch the left and right tab to ground.

 

[Mooseman]

Did you check the fuse/breaker for it? Check the schematics for the actual wiring and fuse number. IIRC, the connector for the liftgate is on the inside of the roof. I think you can see it if you pull the headliner

 

[Petey]

All 3 30 amp fuses under the seat are good. I know only one powers the LGM but it was easier to test all 3 then figure out which one is the one I needed.

Is there a separate breaker for the defogger?

 

[mntegra01]

Hope this can help

 

[Petey]

Thanks for the diagram.

I pulled the trim off the gate, and discovered the the plug is fished out through the hole on the gate. then I checked to see if I had 12v coming out of the purple wire on the LGM (I did) I also then had 12v at the tabs on the glass. Either there was a loose plug or an internally broken wire that I reconnected when I pulled the trim off. I shook all the wires (bungies, in the rubber boot, down by the LGM) around and never lost voltage at the tabs so I put it all back together.

My understanding is all that feeds the LGM is 12v, ground, and Can bus. If the wires in the rubber boot are bad wouldn't I loose all function of the gate electronics (wiper, defrost, locks)

 

[mntegra01]

you could have one wire pinched or broken in a harness, not common, but can happen. I usually just ohm out the wire to check for continuity. Glad it 'fixed' itself! I hate those intermittent problems.

 

[KEEBZ489]

late to the post but my plug was melted a little causing the wire connectoer to be loose. bent the prong fora tighter fit and no problems since