sCALndrel

So I just bought a 2005 C6 Convertible and in my first month of owning it has been to the mechanic 5 times. What happens is I will be driving, then out of nowhere, I get the "service traction" and "service active handling system" messages. Then shortly after I get the "service antilock brakes" "service fuel system" "service vehicle soon" "shocks inoperative" and the fuel, oil pressure, and coolant level gauges all go out. Even worse, the ignition switch illuminates green, and when this happens I cannot start the car again, if turned off, until it goes away. The strange thing is, these problems will go away as quickly as they came. I had the fusebox replaced, no luck. The battery is still new this year, and I checked out and cleaned some of the ground connections up near the battery, yet still no luck. I also thought it was a heat related issue but then again I had a cold start in 60 degree weather and within 30 seconds all of the problems came about.

Lately, I have realized that the interior lights pulsate when this issue occurs, and the voltage gauge bounces between like the 13.2 and 3. Not sure if thats causing the problem

BadAV

It could possibly be one of the large wire harness connectors under the passenger footwell access "flap". Try disconnecting those, cleaning the pins with electrical contact cleaner, adding a little dielectric grease, and reconnecting them.

sCALndrel

Thanks! I will definitely check that out today and update progress. I kind of had a feeling it was something from down there.

Landru

+1
LARGE blue connectors, there're 3.
Use extreme care plugging 'em back in, also.
Very easy to bend one or more of the small delicate pins.

sCALndrel

How exactly should I go about cleaning them? I know I should use electrical contact cleaner and some dielectric grease, but I do not want to damage anything. So should I unplug the battery first and let the pins dry out before putting everything back in? also should I just coat the pins with the chemicals and just let the cleaners do the work (meaning I do not really touch the pins)?

C5 Diag

If the car is not starting coupled with all the messages you are seeing this may be an intermittent communication issue…if you have a scan tool which can read ALL modules I’d see if you have any “U” or communication DTC’s stored.

sCALndrel

I got it scanned at auto zone and it said communication error with ecm bcm and some bus or something, and it also displayed the service antilock brakes and stuff. Other times though, those codes will just disappear but then later reappear with a check engine light. Would this communication problem possibly be related with the mesh things that others said should be cleaned?

Landru

This is not a matter of pins becoming dirty, it's about 'em working themselves loose.
Doesn't take much for intermittent, bizarre crap to occur.

On each blue connector's a 'locking bar', its function obvious, supposedly locks connector together.
Flip bar open, unplug connector, apply dielectric grease.
When replugging simply make sure every male pin's in it's proper hole, gently & firmly push back togther.
Relock bar...done.

What's been reported over C6 run is the flimsy cover over pit depresses by passenger weight xfer'g to one or more plugs.
Over time plug's subject to loosening resulting in wierd itermittent electrical/electronic behavior -- such as you're experiencing.

It's a rare occurance, did give owners seemingly unsolvable headaches.
Cause was discovered quite by accident while an owner fiddled w/ plugs attempting to solve problems.

NOT advocating this is The Source of your issue, granted.
However it might be, worth checking if only to rule-out.

C5 Diag

Helping to know which modules you can’t communicate with helps in a diagnosis and unfortunately 99.99% of “mechanics” wouldn’t even know where to start with a communication issue…below is the information bus for your 05…modules at the bottom left are your low speed or Class 2 bus and all the modules on the right and the BCM is the high speed bus…the arrows show the path from the BCM and then the VCIM (Onstar) and then into and out of each module before ending at the ECM…if you can’t communicate with the BCM or any of the modules on the right side you can start there…since dielectric grease is an insulator and not a contact “enhancer” I wouldn’t use it…Stabilant 22 is my choice…not cheap but the best stuff out there…if this is something that may be over your head find yourself an auto electric or a pure diagnostic shop in your area…they won’t be replacing a bunch of parts !!…video below so you can see this is not a parts changing diagnosis.

SilverC54me

Do not use dielectric grease on the connectors. Dielectric grease is non-conductive and can create additional issue when used inappropriately. It should only be used on the outer surfaces of the connector never on the pins. Also it should only be used on connectors that can get wet.

Gary

KennyPowers

I used the CRC electrical/contact cleaner when I repaired my flood car.. worked great.. I think Home Depot sells a small can for like $6

FatsWaller

I’ve posted this before: I’m not buying the dielectric grease argument. You could argue it out with these guys, who are in the business to know: https://www.nyelubricants.com/myth-g...h-conductivity
In part, their article states

"The results of these tests prove that there is no difference in contact resistance between lubricated and unlubricated connectors. Grease fills in the microscopic valleys of the contact surface and is squeezed out of the asperities, allowing the current to flow and preventing oxidation from occurring. While there is no difference in conductivity, the water resistance test proves that dielectric grease offers protection that unlubricated connectors cannot. In conductive environments, such as water, unlubricated connectors experience current leakage which can result in short circuits. Dielectric grease insulates connectors to prevent current leakage from occurring."

I used this stuff on the underseat connectors when I fixed the air bag light problem, on all the LED lamp replacements, and on the big connectors on the BCM. No problems whatever with connectivity.

BadAV

Never had an issue. A little common sense when applying it inside the connector goes a long way. Clean male/female pins/connectors (spray with electrical contact cleaner, let dry), then a light coat of grease. In my experience it keeps the connections from corroding/oxidizing again.

KennyPowers

Double checking what I had used for the flood car: what I did was CRC QD contact cleaner THEN used the CRC 2-26 electrical spray lube.. The 2-26 is what CRC recommended and it worked very weill.. Home Depot sells cans for $6

IDRIVEAC6

I have had this same or at least a similar problem. The TECHII showed no comms to the BCM. I had all warning lights go off. Car would click but no start. Sometimes the gauges would sweep, fuel gauge went to E and then back no start. Here is what I did:
pulled battery cables, removed battery. Removed battery tray. There are a couple of big connectors on the fender well above the ECM. Checked the wires. Opened each connection. Made sure they were clean. Put some dialectric grease on the pins lightly, put them back together and attached them to the clips on the fender well. Pull the floor mat and carpet panel up on the passenger side floor. Underneath you will find the BCM (body control module) a gatekeeper of network messaging. Open the large blue connectors. Inspect the pins for bending or corrosion. Clean and lightly add dialectric grease. When I closed them I zip tied them tight. I used a 7mm socket to remove the large black connector in the center on the BCM. Cleaned both sides. Inspected the pins. Grease and close. Tighten the center bolt down. Added pink erasers to a couple of points to keep passenger feet from pressing on the BCM. Reinstalled the battery after checking that the grounds around it were still clean. This is very important: when reattaching the battery cables make sure they are properly seated and absolutely tight. Any wiggle and you are bound to have issues. Opened the fuse box. Checked relays especially fuel pump. Clean, grease, replace. Car started with no issues. Battery at 14.3 when idling. I have a 220amp Powermaster alternator installed. Drive, stopped and started several times through the day and night. No issues. Note: this is not the first time I have done this.

myfunz

I would say a bad ECM, just went through this with my '05. Seems to be an issue with these '05 cars. Replaced with a refurbished unit working fine now.

agsus22

We think we have this same issue, as the problem does not happen if I’m not riding with hubby in the passenger seat. We’ve been at the dealership for two months now tying to figure this out. We picked it up today when I found this thread. No issues were present with the codes, etc however it would not shift out of 2nd gear. I’m curious as to how this issue with this passenger fuse box could be connected to the transmission. Any thoughts?