Bill Curlee
CF Senior Member
CI 6-7-8-9 Veteran
St. Jude Donor '08
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Member Since: Jun 2001
Location: Gales Ferry CT

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!)

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

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

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.

PLEASE let me know if you have any questions.

Bill Curlee

updated 02 March 06

Last edited by Bill Curlee; 03-02-2006 at 01:24 PM.