Manny@Dasilva

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IMPORTANT ELECTRICAL INFORMATION

As requested by Riley

Copied and pasted from Bill Curley

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
DSCF0005.jpg


Corrosion inside connector! (You ain't seen nothing yet!)
Chassisgroundconnectordisected001.jpg


Next three photos are of the corrosion found on the connector terminals!
Chassisgroundconnectordisected005.jpg


Chassisgroundconnectordisected004.jpg


Chassisgroundconnectordisected003.jpg


Self tapping ground screw and star washer. This is what you will need if the ground stud breaks off during removal!
Chassisgroundconnectordisected010.jpg


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

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.

C5ZO6pictures012.jpg


C5ZO6pictures013.jpg


C5Chassisgroundlocations.jpg



Thx
Manny@E.C.P
 

Riley P

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Perfect, this is exactly one of the things I want to do in the spring to help keep my car as trouble free as possible.
 

C5Howie

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This is the write up I followed to clear my car of all the weird issues I was having! But I chose the road of removing the ganged connection,I was thinking my way would completely bypass the possibility of it happening again,not a big fan of those types of multi connector.
 

Riley P

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I'm not a big fan of changing factory electrical systems/connectors as I do not know much about the electrical system and the capacities of different connectors. Could you explain what a ganged connection is?
 

C5Howie

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Yes your right you would have to have at least a tiny bit of knowledge and understanding to know what you can and cant modify,so yes just leave it to the pros! Ganged would be multiple circuits sharing one grounding point!
 

Somebuddy

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Am I following this?? Of the aproximately 13 different grounding points are there more than the two ground connectors found under the hood to be cleaned??
 

Riley P

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Yes your right you would have to have at least a tiny bit of knowledge and understanding to know what you can and cant modify,so yes just leave it to the pros! Ganged would be multiple circuits sharing one grounding point!

Very true to leave stuff that you don't know about to the pros. However, sometimes you just have to try stuff to learn it and should it fail, you know better for next time. Learning through failure is totally valid if can live with the consequences and those consequences will not harm others (and your wallet can handle it). I find the most dangerous people are the ones that know a little bit but think they know everything.

Anyway, I am going to learn how to clean my electrical system this spring, but not go so far as to change anything.
 

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