Bill Curlee

Many of you have asked me for help on solving electrical problems and I thought this would be VERY interesting!

My 98 coupe would get the infamous "REDUCED ENGINE POWER", "TRACTION CONTROL FAILURE" and a host of random failure codes. After many, many hours of troubleshooting, replacing the BCM and TAC module, I solved most of the driveability issues. Still getting the random DTC failure codes, I thought that I may be having ground issues. Back in June I cleaned ALL of the chassis grounds and the car virtually stopped throwing the "RANDOM" DTC failure codes. Just moving the wires in the chassis ground connector was enough to change the indications and make the issues stop happening.

I had a chance to speak with some GM C5 Trouble Desk Engineers when I went to Bowling Green KY in April and they pointed out that MANY of the C5 electrical issues can be directly linked to chassis ground problems. The engineer even went as far as to recommending that I chop off the factory under hood chassis ground connectors and combine all of the wires into a single ground lug. Not wanting to just LOP off the factory connector, I took a chance and disassembled one of the ground plug connectors and to my surprise it was indeed full of corroded connections.
I strongly recommend that any C5 owner that has had or who are having electrical issues, examine and clean the chassis ground connectors. This may save you from needlessly replacing expensive electronics modules. Each ground connector can be disassembled and cleaned in about 20 min.

Just cleaning the metal ground connection between the chassis and the plug is only a band aid solution. Now that I look back, when I cleaned my chassis grounds and initially solved my issues, I believe that when the connector is being removed to clean the connection between chassis and the connector, just the wires being moved inside the plug is what changed the indications and made everything work better.
Disassembly of the chassis ground plug and cleaning the contacts inside the connector is the correct method of solving the issue!

I took some pictures of the under hood chassis ground connector and the corrosion that was in it. I cleaned the two connections on the frame rails and the left one was significantly corroded! Taking it apart and cleaning it is a very straight forward procedure and I believe that if you follow this recommendation, you will be on the way to solving the many of the electrical issues.

Here are some detailed pictures of the ground connector and the corrosion that was found inside it!

Picture of under hood Chassis Ground connector G-101



Corrosion inside connector! (You ain't seen nothing yet!)
[IMG][/IMG]

Next three photos are of the corrosion found on the connector terminals!
[IMG][/IMG] [IMG][/IMG] [IMG][/IMG]


Self tapping ground screw and star washer. This is what you will need if the ground stud breaks off during removal!
[IMG][/IMG] [IMG][IMG]

Here are where the chassis ground points are on a C5:









PLEASE let me know if you have any questions. NOTE! All of the pictures that I have of C5 Grounds have been posted on or in this post.

Bill Curlee

updated 02 March 06

HalfMoon

Bill,

Great information. This information should be put into a format for the web and saved on a site. Searches and forum software usually never seem to work right. I've got space and bandwidth if you need it.

Thanks for the info, I'm going to try to remeber to check my grounds on some kind of service schedule once my 04 gets some age to it.

-Tony

mojo1

Very good pictures ,
Thanks for the info!

Bill Curlee

I suck at doing FANCY web stuff! I may try to make this into a TECH TIP. I would have posted more pictures but the forum would not let me! I have more info and pictures if anyone need them!

NOTE! All of the pictures that I have of C5 Grounds have been posted on or in this post.

My 98 electrical issues are 98% solved!!! The only thing that is still kicking my A$% is a Fuel Level Sender problem. After I drive it for a while it goes to empty and I get DIC codes P0461 & P1431

I suspect it is a fuel level sender issue BUT is it the left or the right sensor?? The left one is $400. and the right one is $300. My luck it will be BOTH that are bad!!

To figure it out without using a TECH II, I have to remove both senders and do a resistance check on a full sweep of the float assembly!

Anybody else had this issue??

RESOLVED! Proper use of SEAFOAM or Chevron Fuel System cleaner is several tanks and NO MORE ISSUES!!

Bill

Dan_the_C5_Man

Good info Bill. Thank you.

BHP

Bill, once again, "you da man." I will bookmark this link but you should have Troy put this in tech tips.

HP_Addict

Nice diagnosis. Great information. thanks

Mike Mercury

WOW; the pics tell the whole story. Thanks for spending the time posting them.

slythetove

Couldn't you put some sort of dielectric grease in there to prevent it from recurring?

Bill Curlee

Yes you could! Anything to keep the water and dampness out. I thought about doing it. Maybe I will try it the next time I have to clean it.

BC

sxeC7

Bill, I'm just curious. Do you drive the Vette in winter on salted roads? Also, I assume Gales Ferry is near water. That may accelerate the problem. My 2 cents.

Bill Curlee

Yes,, I drive the car most of the year. The only time I dont drive it is when there is snow on the roads or the roads are real nasty. The road salt could be a factor but why would one connector be nasty and the other be fine? I keep the car clean. Washing the car also plays a role in ground connector corrosion. The water from the hood does drip right on those connectors! The one on the passengers side was wet but had no corrosion.

It's just something to check is you have reoccurring electrical issues for no aparrent reason. Especially problems that come and go.

Bill

Admiral Fairway

Where are the connectors located and how many are there.

GrayC5

Excellent info! Thanks!

Bill Curlee

Admiral Fairway

There are approx 13 chassis grounds. There are two types of ground connectors. The eyelet type and the connector type. The connector type are the ones that are most effected by corrossion. The eyelets seem to be less effected.
There are two connector type ground connections in the engine compartment. Both of the connectors are located on the top of the frame rails directly aft of the head light assemblies. The right connector os inboard of the coolant tank and the left one is inbetween the washer fluid tank and the head light assembly.

Here is a picture of where all of the grounds are located:

[IMG][/IMG] [IMG][/IMG] [IMG][/IMG]

Hope that narrows it down for you.

BC

lt1george

Great post, Thanks Bill.

C66 Racing

Bill,
Great info! Thanks for posting this. Wonder how much of my electrical problems this year have resulted from this type of issue. I'll have to do a detailed check of these.

carpe dm

Great Bill; please do submit it as a Tech Tip.

MarkBradford

Bill,
I have read your posts with great interest. I have a 2000 convertible that just came up with 2 issues on the same day. The Traction Control Failure message started appearing. This has happened randoml before. And also the headlight motor makes a grinding noise when lowering. This noise goes on for 3 or 4 seconds and turns off. I disconnected one lamp to see which was making the grinding and discovered both were doing it. What are the chances of both going out on the same day? Somewhre I read that there is a sensor that controls the lowering and raising of the headlights and that it is located under the passenger side houseing. I'm not too sure how to get to it and also how to test it. Thank you in advance for all your commenst and help.
Mark Bradford
Austin Texas

Bill Curlee

Mark
I doubt if the motor grinding is due to an electrical problem. I am going to hook you up with a head light motor post that will answer all of your questions

http://forums.corvetteforum.com/showthread.php?t=711276

Click on this link, Go to this post and this should provide you with ALL of the necessary info to resolve the issue.

If you have any questions about your other problems, please ask.

Clean your grounds first and make sure your passsengers foot well and BCM is dry.

BC