Long story short, drove all Sunday, got back near the house, and pulled away from a light... hit it... spun the tires a bit.. as always. .and Boom.
reduced engine power and a few codes. Limped it home and in my garage, cpl miles, no big deal. Check the codes and Tps monitor, cpl of those and cple other
minor detail ones and the old H codes, no big deal, i know what they are. I reset the codes and deleted and left on the tender all week, I go out Wednesday, buddy
is going to tint the windows, no big deal, he finishes up and for some reason I turn the key on and get a all "no comm" codes and check engine light, so I start it and the same, like wth. dis the battery cable, and hook the tender direct, go out today, car fires right up and loaded with these damn codes again, no comm. and, reduced engine power, although the engine is running just fine, I do have a some things unplugged but i think would not effect any of this, have the center console out and the radio out, so lots of disconnections. i doubt this would affect it.. maybe i just need to take it for a spin ?
i m lost, no idea. and I can t even delete the no comm readouts.
thanks for any input

 

I had a similar issue and it was my DS seat power harness. Some of the wires were pinched. I’ve also read it can be the door harnesses.

From everything I read this can be a fairly difficult thing to track down; good luck.

 

On c5's there is one wire that connects all the various modules together, a serial data highway of sorts, if that wire shorts to other wires or is cut you will have no comms, as stated previously good luck finding it, could be a seat module, or door module caused by loose or pinched wires in the accordion between door and car.

 

Thanks gentlemen. I'm going to check the accordion wire going in the passenger door and see what's in there. I have no power seats are replace the seats with non power so that shouldn't be an issue.

 

Sounds like a serial data issue with ALL no comms...if any of the modules lose power or ground that power or ground may back feed onto the single wire data line...has to find a way “home” so it jumps on the data line and BOOM...all no comms !!...usually with all no comms you’ll see a no start or a start and stall !!...yes, check the 6 wire connector that sits in that accordion boot !!

 

That is my mission tonight, it does start and idles and revs fine, even tho says reduced engine power.
Thanks very much sir.

 

Okay so I'm out messing around with it the key is in the ignition or open the doors none of the light comes on no ding ding ding no nothing the battery is fully charged at 12 and a half. I turn the key on and then the light show begins and the messages I'm kind of at a loss here but I'll start with this accordion plug in the passenger door I guess and see what's going on there I'm just amazed that I'm standing here looking at it and no flipping lights on

 

With the key ON are you receiving all the DIC messages...low fuel, service engine soon etc...also is the water temp gauge maxed out and the fuel gage shows empty ???

 

wow. you hit it all. i never noticed the water temp but yes to all the rest. and no interior lights and hatch won t pop, but fuel door does.

 

tried digging the wires out of the driver door,, not a lot of room there, and am not cutting the boot to get the wires out in the open..
must be a way to do it tho..

 

A quick check to see if you have a serial data issue...find the 2 splice packs (pictured with comb removed) to the left of the BCM in the passengers footwell...pop of the bus bar (we call it a comb) on the splice pack with the 4 or 5 wires... now turn the key on and see if all that craziness goes away !!

 

saw them earlier.. and played with them, did not take them apart tho
in the morning... then what will that tell me

 

Confirmed, the temp pins.. unplug the hair combs, and the madness continues...
i m lost on this one, i hate electrical issues.

 

Did you remove both combs or only the one ??...try removing both and see what happens with the key on !!...all the modules should be isolated from the network...the car won’t start but see if all the craziness disappears...and clean both combs with sandpaper or wire brush...had a member a while back whose comb looked ok but had enough corrosion to cause a no comm !!

 

i pulled them both out, turned the key and the bells and whistles continue... they looked fine,,I while give them a brush and light
buff with some emery cloth... see what transpires from that.
i very much appreciate your guidance and help here.

 

If you have a DVOM probe pin 2 on the DLC (where a scan tool hooks up to) with key on and see if you see 12 volts or ground there !!...with a voltmeter you will only see maybe .3 or .4 volts and it will be fluctuating...it is really a 0-7 volt square wave but you won’t see that with a DVOM...it’s refresh rate is too slow !!...this is what the data line looks like on my scope.

 

we gained a bit of headway, the mirror light now comes on along with the door lights and the hatch now releases..
still no comm tho when i go to check codes... fwiw the battery is fully charged and on a tender, did a load test on it this morning.

 

where do i find the DLC ?

 

It’s pretty far up under the drivers side. Behind the knee bolster.

 

That kind of bites gettin there. I do have the radio out so may make it easier.
I am wondering if my issue is on the passenger side of the car oh, I don't know if that's possible oh, I've been working on cars for 40 years and haven't come across anything like this but I'm never, because as I mentioned earlier the interior lights now come on on the driver side collide on the football does not come on yet, but the hatch opens and the lights come on in the hatch I'm not sure 4 to start pulling and gouging.