? re Drivers seat switch/plug causing data bus issues

[Chewy]

I have an '07 coupe with pretty much all the options. I've done a few searches on this and other forums, so I think I know what the problem MAY be, but here are the symptoms....

I'll be driving along when everything on the dash just starts going bonkers:
-airbag light comes on
-fuel gauge goes to empty
-security light (yellow lock above headlight indicator) comes on
-oil pressure drops to 0
-coolant temp drops to 0
-DIC alarms for "service fuel" and "service ABS"
-radio turns off
-A/C clutch disengages (air keeps blowing, only it's HOT)
-windows stop working
-TPMS are all blank, tire idiot light flashes then goes solid
-door won't open (with brake up) until car is turned off
-if the headlight switch is in 'auto' the lights will come on
-dimmer control tells everything inside the car that it's night time

I have a OBDII/CAN code scanner, but there are NO codes shown. I've even managed to get the scanner plugged in while everything was acting up, and still no codes (but the 'live data' all looked correct).

I'm currently 850 miles from home, but I did manage to isolate the problem to the drivers seat on my way here. Whenever things go bad, I found that all I have to do is lift my cheeks up off of the drivers seat and everything almost instantly goes back to normal. I'm able to repeat the problem and the 'fix' almost at will, so I'm as sure as I can be that my seat is causing the issue. I tried rotating the big connector at the rear of the seat frame up to the top of the bar, but nothing changed.

Once everything goes back to normal, the fuel gauge sometimes returns to the proper level and sometimes stays at empty until I restart the car. But the security light always stays on until the car is restarted.

I've read posts about having a loose wire in the seat harness that can cause the airbag light to come on, but could that be causing all of the other computers on the class2 data wire to go nuts also?

I'm out of my 3/36 warranty, but I do have a GMPP with $200 deductible. Once I get home I'd prefer to just pull the seat and fix it myself if possible, but I'll go to the dealer if you guys think it may be more than just a loose connection.

[NORTY]

When you lift your cheeks off the seat surface, are you pulling on the steering wheel column? There's a recall for the wiring inside the column (but it usually shows "ACTIVE HANDLING ACTIVATED." On the DIC.)
With all those symtoms, I'd look for a ground. What's your static battery voltage?

[froggy47]

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[Chewy]

Originally Posted by NORTY

When you lift your cheeks off the seat surface, are you pulling on the steering wheel column?

Nope, not even touching it when I was in the parking lot, just using the dead pedal as leverage.

Originally Posted by NORTY

What's your static battery voltage?

14v +/- .2 with AC and fans cycling on/off.

[Chewy]

I did another 150 miles today, I think I have the problem area isolated to one of two spots.

It's either in the rear passenger quarter of the center leather portion of the seat, or somewhere along the center/outer seam closest to the door. Whenever I sit the way I want to, centered and towards the rear of the seat, the problem starts happening within 5 minutes. If I sit more towards the center of the car, with right cheek on the outer raised cushion and left cheek near center of seat, no problems at all, but that isn't very comfy and it's kinda hard to shift.

EVERY TIME things start going bad all I have to do is lift up off the seat and it all goes back to normal (except the yellow lock security light stays on until next restart).

My only real concern at this point is that all of the other gauges going bonkers may point to the SDM module itself, and not just a loose connection or bad sensor in the seat. I was hoping one of the pros on this site had seen similar problems before and could point me at the right component.

[c4c5specialist]

HI there,

HERE is the biggest issue.

If you had a NO COMM and your scan tool was still receiving data, then you DO NOT HAVE A LOSS OF COMMUNICATIONS.

SO THEN THE NO COMM IS FALSE AND YOU NEED TO ISOLATE EACH INDIVIDUAL MODULE>

The seat control module, heated seat module are both there and are on the low speed lan bus, NOT THE HIGH SPEED dual wired LAN, which goes nowhere near the seat.

That being said, you need to confirm communications with EACH INDIVIDUAL CONTROL MODULE>

OBD/CAN code scanner can communicate at the exact same time as your obtaining data, there is something else amiss.

Allthebest, c4c5

[LLC5]

Are there any aftermarket accessories on the vehicle?

[froggy47]

If this model has keyless ignition, you aren't sitting on the key fob, are ya?

:)

[Chewy]

Originally Posted by LLC5

Are there any aftermarket accessories on the vehicle?

Not any more.

When this first started to happen my initial thought was the GMCO radio interface, so I disconnected the data line and used the wiper circuit to trigger the radio. Nothing changed, except now my radio doesn't turn off when the other stuff goes nuts.

I also had an accessory valet, which is now removed.

Originally Posted by froggy47

If this model has keyless ignition, you aren't sitting on the key fob, are ya?

:)

NO

Originally Posted by c4c5specialist

That being said, you need to confirm communications with EACH INDIVIDUAL CONTROL MODULE

I guess I'll unplug the modules one at a time and see if the problem goes away.

[LLC5]

It could be a broken wire, or wire to terminal end, or even a pin fit issue inside a harness connector. When you pull the seat you should be able to find it since you can get it act up. Has the drivers seat ever been out of the vehicle for any reason?