Many 2011 and prior GM^® passenger cars or trucks may exhibit multiple diagnostic trouble codes (DTCs) from different modules and have numerous electrical issues. The repair may be as simple as applying dielectric grease to the appropriate connectors. Why? It helps eliminate the effects of fretting corrosion.

CAUTION: Dielectric grease has insulating properties. Only apply enough dielectric grease with a nylon bristle brush to lightly coat the pins. Too much grease could cause the spring-loaded connector pins to expand and create a poor connection. Also, use ONLY a premium quality dielectric grease. Low quality or the incorrect type of grease could cause a short circuit between pins.

Fretting corrosion is a buildup of nonconductive oxidized debris between the electrical surfaces in a connector. It can be caused by vibration, thermal cycling, poor connections, terminal retention or micro-motion. Fretting corrosion looks like little dark smudges on electrical terminals and appears where the actual electrical contact is being made. In less severe cases, you may need a magnifying glass to see or identify it.

This type of corrosion causes a rapid increase in resistance, which leads to electrical problems. On low-current signal circuits this condition may cause high resistance, resulting in intermittent connections. On high-current power circuits this condition may cause permanent increases in circuit resistance and could cause a device to become inoperative or overheated.

Here is a list of conditions caused by fretting corrosion:

• An intermittent no crank/no start
• Intermittent malfunction indicator lamp (MIL) illumination
• Intermittent warning lights on in dash
• Intermittent service message(s) displayed
• No module communication
• Numerous DTCs set by various control modules

GM recommends that you do not replace any control module or component based on a DTC alone, especially if the condition is intermittent and cannot be duplicated. If you can no longer duplicate an intermittent problem after you disconnect and reconnect a connector, further diagnose that connector.

Repair Procedures

NOTE: The testing and repair procedures mentioned in this repair procedure are available in ALLDATA Repair Pro, ALLDATA Repair S3000, ALLDATA Collision or ALLDATA Collision S3500.

Use the following procedures to diagnose and correct the conditions listed above.

1. Install a scan tool and perform a diagnostic system check. Retrieve and record any existing history or current DTCs from all of the control modules.
   
   If any DTC(s) are set, refer to the DTC diagnostic procedure to identify the connector(s) of the control module or component that may be causing the condition.
   
   If there are no DTC(s) set, refer to a symptom chart to identify the connector(s) of the control module or component that may be causing the condition.
2. Once the control module or component is identified, use the appropriate DTC diagnostics, symptom charts, schematics, component connector views and component locator documents to find and disconnect the affected harness connector(s) which are causing the condition.
3. First, remove any rubber connector seals and clean the connectors with the appropriate electrical contact cleaner. Then, with a small nylon bristle brush, lightly coat the male pin side of the affected connector with a very small amount of premium-grade dielectric grease. You can also apply a light coat of dielectric grease to the connector’s rubber seal, which helps keep air out and reduce oxidation.
   
   
   Example of Too Much Grease.
   
   NOTE: DO NOT apply an excessive amount of dielectric grease to the connector (see image). Hydro-lock may result when attempting to push the connectors together, which can force the connector and the spring-loaded pins apart. Use only a clean nylon brush dedicated to the repair of these conditions and lightly coat the pins.
4. Reconnect the affected connector(s) and wipe away any excess lubricant that may be present. Reinstall the rubber connector seals.
5. Attempt to duplicate the condition by using the following information:

• DTC Diagnostic Procedure
• Circuit/System Description
• Conditions for Running the DTC
• Diagnostic Aids
• Circuit/System Verification

If the condition cannot be duplicated, the repair is complete. If the problem can be duplicated, then follow the appropriate DTC, symptom or circuit/system testing procedure. There are many reasons for module and component failures. Dielectric grease may help you fix many of them.

Written by the ALLDATA^® Community^SM Automotive Diagnostic Team, a select group of automotive experts dedicated to helping technicians fix hard-to-repair vehicles more efficiently. To meet the team, click here.