Sierra 2500 Denali 2WD V8-6.0L (2011)
Testing for Terminal Fretting
Some intermittent conditions can be caused by wire terminal fretting corrosion. Fretting corrosion is a build-up of insulating, oxidized wear debris that
can form when there is a small motion between electrical contacts. The oxidized wear debris can pile up enough at the electrical contact spots that the
electrical resistance across the connection increases. Movement between the contacting surfaces as small as 10 to 100 microns can cause fretting. To put
this in perspective, a sheet of paper is about 100 microns thick, so fretting motion is small and hard to see. Vibration and thermal expansion/contraction
are the main sources that create fretting motion. Since vehicles vibrate and can experience large temperature swings, they are a good source for fretting
motion. Tin, copper, nickel, and iron surfaces are all susceptible to fretting corrosion. Fretting corrosion can be difficult to see but it looks like small,
dark smudges on the terminals contact surface.
To correct a fretting condition disconnect the suspect connector and add Nyogel lubricant 760G (dielectric grease) to both sides of the connector
terminals. Then reconnect the connector and wipe away any excess lubricant. This will correct the additional terminal contact resistance due to the
terminal fretting corrosion.
Testing for Proper Terminal Contact
It is important to test terminal contact at the component and any inline connectors before replacing a suspect component. Mating terminals must be
inspected to ensure good terminal contact. A poor connection between the male and female terminal at a connector may be the result of contamination or
deformation.
Contamination may be caused by the connector halves being improperly connected. A missing or damaged connector seal, damage to the connector
itself, or exposing the terminals to moisture and dirt can also cause contamination. Contamination, usually in the underhood or underbody connectors,
leads to terminal corrosion, causing an open circuit or intermittently open circuit.
Deformation is caused by probing the mating side of a connector terminal without the proper adapter. Always use the J 35616 when probing connectors.
Other causes of terminal deformation are improperly joining the connector halves, or repeatedly separating and joining the connector halves.
Deformation, usually to the female terminal contact tang, can result in poor terminal contact causing an open or intermittently open circuit.
Testing for Proper Terminal Contact in Bussed Electrical Centers (BEC)
It is very important to use the correct test adapter when testing for proper terminal contact of fuses and relays in a bussed electrical center (BEC). Use J
35616-35 to test for proper terminal contact. Failure to use J 35616-35 can result in improper diagnosis of the BEC.
Follow the procedure below in order to test terminal contact:
1. Separate the connector halves.
2. Visually inspect the connector halves for contamination. Contamination may result in a white or green build-up within the connector body or
between terminals. This causes high terminal resistance, intermittent contact, or an open circuit. An underhood or underbody connector that shows
signs of contamination should be replaced in its entirety: terminals, seals, and connector body.
3. Using an equivalent male terminal from the J-38125 , test that the retention force is significantly different between a good terminal and a suspect
terminal. Replace the female terminal in question.
Flat Wire (Dock and Lock) Connectors
There are no serviceable parts for flat wire (dock and lock) connectors on the harness side or the component side.
Follow the procedure below in order to test terminal contact:
1. Remove the component in question.
2. Visually inspect each side of the connector for signs of contamination. Avoid touching either side of the connector as oil from your skin may be a
source of contamination as well.
3. Visually inspect the terminal bearing surfaces of the flat wire circuits for splits, cracks, or other imperfections that could cause poor terminal
contact. Visually inspect the component side connector to ensure that all of the terminals are uniform and free of damage or deformation.
4. Insert the appropriate adapter from the on the flat wire harness connector in order to test the circuit in question.
Control Module/Component Voltage and Grounds
Poor voltage or ground connections can cause widely varying symptoms.
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Test all control module voltage supply circuits. Many vehicles have multiple circuits supplying voltage to a control module. Other components in
the system may have separate voltage supply circuits that may also need to be tested. Inspect connections at the module/component connectors,
fuses, and any intermediate connections between the voltage source and the module/component. A test lamp or a DMM may indicate that voltage
is present, but neither tests the ability of the circuit to carry sufficient current. Ensure that the circuit can carry the current necessary to operate the
component. Refer to Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Circuit Testing/Circuit Testing) and Power Distribution Schematics (See: Diagrams/Electrical Diagrams/Starting and Charging/Power
