Testing Wiring Systems for Intermittent & Poor Connections GMC Savana I

SERVICE PRECAUTIONS

INTERMITTENT OR POOR CONNECTIONS

Note. Tools Required: GM-Approved Terminal Test Kit (J-35616-C) Terminal Repair Kit (J-38125-D) Instruction Manual (J-38125-4) Flat-Wire Probe Adapter (J-42675)

Most intermittent conditions are caused by faulty electrical connections or wiring. Inspect for the following items

1. Wiring broken inside the insulation.
2. Poor connection between the male and female terminal at a connector.
3. Poor terminal to wire connection. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over the wire insulation rather than the wire itself and corrosion in the wire to terminal contact area, etc.
4. Wire insulation which is rubbed through. This causes an intermittent short as the bare area touches other wiring or parts of the vehicle.
5. See «Inducing Intermittent Fault Conditions»(/gmc/savana/i-1996-2002/remont/body-electrical/#testing-wiring-systems-for-intermittent-poor-connections__inducing-intermittent-fault-conditions) in order to duplicate the conditions required in order to verify the complaint.
6. See «Testing for Electrical Intermittents»(/gmc/savana/i-1996-2002/remont/body-electrical/#testing-wiring-systems-for-intermittent-poor-connections__testing-for-electrical-intermittents) for test procedures to detect intermittent open, high resistance, short to ground, and short to voltage conditions.
7. See Scan Tool Snapshot Procedure for advanced intermittent diagnosis.

Testing for Proper Terminal Contact

It is important to test terminal contact at the component and any in-line 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 GM-approved terminal test kit 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.

Round Wire Connectors

Follow the procedure to test terminal contact of Metri-Pack or 56 series terminals. Refer to the terminal repair kit or the instruction manual for terminal identification. Follow the procedure 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 terminal repair kit, 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 & 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 flat-wire probe adapter on the flat wire harness connector in order to test the circuit in question.

Inducing Intermittent Fault Conditions

In order to duplicate the customer's concern, it may be necessary to manipulate the wiring harness if the malfunction appears to be vibration related. Manipulation of a circuit can consist of a wide variety of actions, including

1. Wiggling the harness.
2. Disconnecting a connector and reconnecting.
3. Stressing the mechanical connection of a connector.
4. Pulling on the harness or wire in order to identify a separation/break inside the insulation.
5. Relocating a harness or wires.

All these actions should be performed with some goal in mind. For instance, with a scan tool connected, wiggling the wires may uncover a faulty input to the control module. The snapshot option would be appropriate here. See Scan Tool Snapshot Procedure for advanced intermittent diagnosis. You may need to load the vehicle in order to duplicate the concern. This may require the use of weights, floor jacks, jackstands, frame machines, etc. In these cases you are attempting to duplicate the concern by manipulating the suspension or frame. This method is useful in finding harnesses that are too short and their connectors pull apart enough to cause a poor connection. A Digital Multi-Meter (DMM) set to Peak Min/Max mode and connected to the suspect circuit while testing can yield desirable results. See

Testing for Electrical Intermittents

Certainly, using the senses of sight, smell, and hearing while manipulating the circuit can provide good results as well.

There may be instances where circuit manipulation alone will not meet the required criteria for the fault condition to appear. In such cases it may be necessary to expose the suspect circuit to other conditions while manipulating the harness. Such conditions would include high moisture conditions, along with exceptionally high or low temperatures. The following discusses how to expose the circuit to these kinds of conditions.

Salt Water Spray

Some compounds possess the ability to conduct electricity when dissolved in water such as ordinary salt. By mixing table salt with water in sufficient quantities, you can enhance the conductive properties of water so that any circuit which may be sensitive to moisture will more readily fail when liberally sprayed with this mixture.

Mixing 0.35L (12 oz) of water with approximately 1 tablespoon of salt will yield a salt solution of 5 percent. Fill a normal spray bottle with this mixture. This mixture is sufficient to enhance the water's own conductivity. This may cause the circuit to fail more easily when sprayed. Once the mixture is completed, spray the suspect area liberally with the solution. Then, while monitoring either a scan tool or DMM, manipulate the harness as discussed previously.

High Temperature Conditions

Note. Tools Required: Heat Gun (J-25070)

If the complaint tends to be heat related, you can simulate the condition using the J-25070.

Using the heat gun, you can heat up the suspected area or component. Manipulate the harnesses under high temperature conditions while monitoring the scan tool or DMM to locate the fault condition.

The high temperature condition may be achieved simply by test driving the vehicle at normal operating temperature. If a heat gun is unavailable, consider this option to enhance your diagnosis. This option does not allow for the same control, however.

Low Temperature Conditions

Depending on the nature of the fault condition, placing a fan in front of the vehicle while the vehicle is in the shade can have the desired effect.

If this is unsuccessful, use local cooling treatments such as ice or a venturi type nozzle (one that provides hot or cold air). This type of tool is capable of producing air stream temperatures down to -18°C (0°F) from one end and 71°C (160°F) from the other. This is ideally suited for localized cooling needs.

Once the vehicle, component, or harness has been sufficiently cooled, manipulate the harness or components in an effort to duplicate the concern.

Testing for Electrical Intermittents

Perform the following procedures while wiggling the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the test equipment.

1. «Testing for Short to Ground»(/gmc/savana/i-1996-2002/remont/body-electrical/#testing-wiring-systems-for-intermittent-poor-connections__testing-for-short-to-ground)
2. «Testing for Continuity»(/gmc/savana/i-1996-2002/remont/body-electrical/#testing-wiring-systems-for-intermittent-poor-connections__testing-for-continuity)
3. «Testing for a Short to Voltage»(/gmc/savana/i-1996-2002/remont/body-electrical/#testing-wiring-systems-for-intermittent-poor-connections__testing-for-a-short-to-voltage) NOTE: The J-39200 must be used in order to perform the following procedure since the J-39200 can monitor current, resistance or voltage while recording the minimum (MIN), and maximum (MAX) values measured.

If the fault is not identified, perform the procedure below using the MIN MAX feature on the J-39200 DMM. This feature allows you to manipulate the circuit without having to watch the J-39200 . The J-39200 will generate an audible tone when a change is detected.

1. Connect the J-39200 to both sides of a suspected connector (still connected), or from one end of a suspected circuit to the other. See «Troubleshooting with a Digital Multimeter»(/gmc/savana/i-1996-2002/remont/body-electrical/#testing-wiring-systems-for-intermittent-poor-connections__troubleshooting-with-a-digital-multimeter) for information on connecting the J-39200 to the circuit.
2. Set the rotary dial of the J-39200 to the V (AC) or V (DC) position.
3. Press the range button of the J-39200 in order to select the desired voltage range. NOTE: The 100 ms RECORD mode is the length of time an input must stay at a new value in order to record the full change.
4. Press the MIN MAX button of the J-39200 . The J-39200 displays 100 ms RECORD and emits an audible tone (beep).
5. Simulate the condition that is potentially causing the intermittent connection, either by wiggling the connections or the wiring, test driving, or performing other operations. See «Inducing Intermittent Fault Conditions»(/gmc/savana/i-1996-2002/remont/body-electrical/#testing-wiring-systems-for-intermittent-poor-connections__inducing-intermittent-fault-conditions) .
6. Listen for the audible Min Max Alert which indicates that a new minimum or maximum value has been recorded.
7. Press the MIN MAX button once in order to display the MAX value and note the value.
8. Press the MIN MAX button again in order to display the MIN value and note the value.
9. Determine the difference between the MIN and MAX values. If the variation between the recorded MIN and MAX voltage values is 1 volt or greater an intermittent open or high resistance condition exists. Repair the condition as necessary. If the variation between the recorded MIN and MAX voltage values is less than 1 volt an intermittent open or high resistance condition does not exist.

Testing for Short to Ground

Note. Before proceeding, see SERVICE PRECAUTIONS .

The following procedures test for a short to ground in a circuit.

With a DMM

1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.
2. Disconnect the load.
3. Set the rotary dial of the DMM to the ohms position.
4. Connect 1 lead of the DMM to 1 end of the circuit to be tested.
5. Connect the other lead of the DMM to a good ground.
6. If the DMM does NOT display infinite resistance (OL), there is a short to ground in the circuit.

With a Test Lamp

1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.
2. Disconnect the load.
3. Connect 1 lead of the test lamp to battery positive voltage.
4. Connect the other lead of the test lamp to 1 end of the circuit to be tested.
5. If the test lamp illuminates, there is a short to ground in the circuit.

Fuse Powering Several Loads

1. Review the system schematic and locate the fuse that is open.
2. Open the first connector or switch leading from the fuse to each load.
3. Connect a DMM across the fuse terminals (be sure that the fuse is powered). When the DMM displays voltage the short is in the wiring leading to the first connector or switch. If the DMM does not display voltage refer to the next step.
4. Close each connector or switch until the DMM displays voltage in order to find which circuit is shorted.

Testing for Continuity

Note. Before proceeding, see SERVICE PRECAUTIONS .

The following procedures verify good continuity in a circuit.

1. Set the rotary dial of the DMM to the ohms position.
2. Disconnect the power feed (i.e. fuse, control module) from the suspect circuit.
3. Disconnect the load.
4. Press the MIN MAX button on the DMM.
5. Connect one lead of the DMM to one end of the circuit to be tested.
6. Connect the other lead of the DMM to the other end of the circuit.
7. If the DMM displays low or no resistance and a tone is heard, the circuit has good continuity.

1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.
2. Disconnect the load.
3. Connect 1 lead of the test lamp to 1 end of the circuit to be tested.
4. Connect the other lead of the test lamp to battery positive voltage.
5. Connect the other end of the circuit to ground.
6. If the test lamp illuminates (full intensity), then the circuit has good continuity.

Testing for a Short to Voltage

Note. Before proceeding, see SERVICE PRECAUTIONS .

The following procedure tests for a short to voltage in a circuit

1. Set the rotary dial of the DMM to the V (DC) position.
2. Connect the positive lead of the DMM to 1 end of the circuit to be tested.
3. Connect the negative lead of the DMM to a good ground.
4. Turn ON the ignition and operate all accessories.
5. If the voltage measured is greater than 1 volt, there is a short to voltage in the circuit.

Troubleshooting with a Digital Multimeter

Note. Before proceeding, see SERVICE PRECAUTIONS .

The J-39200 instruction manual is a good source of information and should be read thoroughly upon receipt of the DMM as well as kept on hand for future reference.

A DMM should be used instead of a test lamp in order to test for voltage in high impedance circuits. While a test lamp shows whether voltage is present, a DMM indicates how much voltage is present.

The ohmmeter function on a DMM shows how much resistance exists between 2 points along a circuit. Low resistance in a circuit means good continuity.

Note. Disconnect the power feed from the suspect circuit when measuring resistance with a DMM. This prevents incorrect readings. DMMs apply such a small voltage to measure resistance that the presence of voltages can upset a resistance reading.

Diodes and solid state components in a circuit can cause a DMM to display a false reading. To find out if a component is affecting a measurement take a reading once, then reverse the leads and take a second reading. If the readings differ the solid state component is affecting the measurement.

Following are examples of the various methods of connecting the DMM to the circuit to be tested

1. Backprobe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while you perform other operations or test driving. See «Probing Electrical Connectors»(/gmc/savana/i-1996-2002/remont/body-electrical/#testing-wiring-systems-for-intermittent-poor-connections__probing-electrical-connectors) .
2. Disconnect the harness at both ends of the suspected circuit where it connects either to a component or to other harnesses.
3. If the system that is being diagnosed has a specified pinout or breakout box, it may be used in order to simplify connecting the DMM to the circuit or for testing multiple circuits quickly.

Troubleshooting with a Test Lamp

Note. Before proceeding, see SERVICE PRECAUTIONS .

Note. Tools Required: 12-Volt Unpowered Test Lamp (J-35616-200)

A test lamp can simply and quickly test a low impedance circuit for voltage.

The J 35616-200 is Micro-Pack compatible and comprised of a 12-volt light bulb with an attached pair of leads.

To properly operate this tool use the following procedures.

When testing for voltage

1. Attach 1 lead to ground.
2. Touch the other lead to various points along the circuit where voltage should be present.
3. When the bulb illuminates, there is voltage at the point being tested.

When testing for ground

1. Attach 1 lead to battery positive voltage.
2. Touch the other lead to various points along the circuit where ground should be present.
3. When the bulb illuminates, there is ground at the point being tested.

Probing Electrical Connectors

Note. Always be sure to reinstall the Connector Position Assurance (CPA) and Terminal Position Assurance (TPA) when reconnecting connectors or replacing terminals.

Frontprobe

Disconnect the connector and probe the terminals from the mating side (front) of the connector.

Note. Before proceeding, see SERVICE PRECAUTIONS .

Refer to the following table as a guide in selecting the correct test adapter for frontprobing connectors

FRONTPROBING TEST ADAPTERS GUIDE

Backprobe

Note. Backprobe connector terminals only when specifically required in diagnostic procedures. Do not backprobe a sealed (Weather Pack(R)) connector, less than a 280 series Metri-Pack connector, a Micro-Pack connector, or a flat wire (dock and lock) connector. Backprobing can be a source of damage to connector terminals. Use care in order to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large of a test probe. After backprobing any connector, inspect for terminal damage. If terminal damage is suspected, test for proper terminal contact.

Do not disconnect the connector and probe the terminals from the harness side (back) of the connector.

See also:
• Inducing Intermittent Fault Conditions
• Testing for Electrical Intermittents
• Testing for Short to Ground
• Testing for Continuity
• Testing for a Short to Voltage
• Troubleshooting with a Digital Multimeter
• SERVICE PRECAUTIONS
• Probing Electrical Connectors