Wiring Systems (Diagnostic Information and Procedures) Chevrolet Chevy Express G3500

Fastener Tightening Specifications

Fastener Tightening Specifications

Utility/Van Zoning

All grounds, in-line connectors, pass-through grommets, and splices have identifying numbers that correspond to where they are located in the vehicle. The following table explains the numbering system.

Scheme 1

Utility/Van Zoning

Electrical Symbols

Electrical Symbols OLD Symbol NEW Symbol Description Supplemental Inflatable Restraint (SIR) or Supplemental Restraint System (SRS) Icon This icon is used to alert the technician that the system contains SIR/SRS components that require certain precautions before servicing. On-Board Diagnostic (OBD II) Icon This icon is used to alert the technician that the circuit is essential for proper OBD II emission controls circuit operation. Any circuit which, if it fails, causes the malfunction indicator lamp (MIL) to turn on, is identified as an OBD II circuit. Important Icon This icon is used to alert the technician that there is additional information that will aid in servicing a system. Voltage Indicator Boxes These boxes are used on schematics to indicate when voltage is present at a fuse. Partial Component When a component is represented in a dashed box, the component or its wiring is not shown in its entirety. Entire Component When a component is represented in a solid box the component or its wiring is shown in its entirety. Fuse Circuit Breaker Fusible Link Connector Attached to Component Pigtail Connector Bolt On or Screw On Eyelet Terminal Inline Harness Connector Splice Chassis Ground Case Ground Single Filament Light Bulbs Double Filament Light Bulb Light Emitting Diodes Capacitor Battery Variable Battery Resistor Variable Resistor Position Sensor I/O Resistors I/O Switches Diode Heating Element Motor Solenoid Coil Antenna Twisted Wires Shield Switches Single Pole/Throw Relay - Normally Open Single Pole/Throw Relay - Normally Closed

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

Scheme 23

Basic Knowledge Required

Without a basic knowledge of electricity, it will be difficult to use the diagnostic procedures contained in the service manual. You should understand the basic theory of electricity, and know the meaning of voltage (volts), current (amps), and resistance (ohms). You should also be able to read and understand a wiring diagram, as well as understand what happens in a circuit with an open or a shorted wire.

Checking Aftermarket Accessories

Do not connect aftermarket accessories into the following circuits

1. SIR circuits, all such circuits are indicated on circuit diagrams with the SIR symbol.
2. OBD II circuits, all such circuits are indicated on circuit diagrams with the OBD II symbol.

Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problems.

Possible causes of vehicle problems related to aftermarket accessories include

1. Power feeds connected to points other than the battery
2. Antenna location
3. Transceiver wiring located too close to vehicle electronic modules or wiring
4. Poor shielding or poor connectors on antenna feed line
5. Check for recent service bulletins detailing installation guidelines for aftermarket accessories.

Circuit Testing

The Circuit Testing section contains the following diagnostic testing information. Using this information along with the diagnostic procedures will identify the cause of the electrical malfunction.

1. «Using Connector Test Adapters»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__using-connector-test-adapters)
2. «Probing Electrical Connectors»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__probing-electrical-connectors)
3. «Troubleshooting with a Digital Multimeter»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__troubleshooting-with-a-digital-multimeter)
4. «Troubleshooting with a Test Lamp»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__troubleshooting-with-a-test-lamp)
5. «Using Fused Jumper Wires»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__using-fused-jumper-wires)
6. «Measuring Voltage»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__measuring-voltage)
7. «Measuring Voltage Drop»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__measuring-voltage-drop)
8. «Measuring Frequency»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__measuring-frequency)
9. «Testing for Continuity»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__testing-for-continuity)
10. «Testing for Short to Ground»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__testing-for-short-to-ground)
11. «Testing for a Short to Voltage»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__testing-for-a-short-to-voltage)

Using Connector Test Adapters

Note. Do not insert test equipment probes (DVOM etc.) into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal will cause a poor connection, which will result in a system failure. Always use the J-35616 GM-Approved Terminal Test Kit or the J 42675 Flat-Wire Probe Adapter in order to front probe terminals. Do not use paper clips or other substitutes to probe terminals. When using the J-35616 GM-Approved Terminal Test Kit, ensure the terminal test adapter choice is the correct size for the connector terminal. Do not visually choose the terminal test adapter because some connector terminal cavities may appear larger than the actual terminal in the cavity. Using a larger terminal test adapter will damage the terminal. Refer to the J-35616 GM-Approved Terminal Test Kit label on the inside of the J-35616 GM-Approved Terminal Test Kit for the correct adapter along with the connector end view for terminal size.

Probing Electrical Connectors

Frontprobe

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

Note. Do not insert test equipment probes (DVOM etc.) into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal will cause a poor connection, which will result in a system failure. Always use the J-35616 GM-Approved Terminal Test Kit or the J 42675 Flat-Wire Probe Adapter in order to front probe terminals. Do not use paper clips or other substitutes to probe terminals. When using the J-35616 GM-Approved Terminal Test Kit, ensure the terminal test adapter choice is the correct size for the connector terminal. Do not visually choose the terminal test adapter because some connector terminal cavities may appear larger than the actual terminal in the cavity. Using a larger terminal test adapter will damage the terminal. Refer to the J-35616 GM-Approved Terminal Test Kit label on the inside of the J-35616 GM-Approved Terminal Test Kit for the correct adapter along with the connector end view for terminal size.

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

Probing Electrical Connectors

Backprobe

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

Troubleshooting with a Digital Multimeter

Note. Do not insert test equipment probes (DVOM etc.) into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal will cause a poor connection, which will result in a system failure. Always use the J-35616 GM-Approved Terminal Test Kit or the J 42675 Flat-Wire Probe Adapter in order to front probe terminals. Do not use paper clips or other substitutes to probe terminals.When using the J-35616 GM-Approved Terminal Test Kit, ensure the terminal test adapter choice is the correct size for the connector terminal. Do not visually choose the terminal test adapter because some connector terminal cavities may appear larger than the actual terminal in the cavity. Using a larger terminal test adapter will damage the terminal. Refer to the J-35616 GM-Approved Terminal Test Kit label on the inside of the J-35616 GM-Approved Terminal Test Kit for the correct adapter along with the connector end view for terminal size.

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.

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. Refer to «Probing Electrical Connectors»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__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.

Tools Required

J 35616-200 12-Volt Unpowered Test Lamp. See Special Tools and Equipment .

Troubleshooting with a Test Lamp

Note. Do not insert test equipment probes (DVOM etc.) into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal will cause a poor connection, which will result in a system failure. Always use the J-35616 GM-Approved Terminal Test Kit or the J 42675 Flat-Wire Probe Adapter in order to front probe terminals. Do not use paper clips or other substitutes to probe terminals.When using the J-35616 GM-Approved Terminal Test Kit, ensure the terminal test adapter choice is the correct size for the connector terminal. Do not visually choose the terminal test adapter because some connector terminal cavities may appear larger than the actual terminal in the cavity. Using a larger terminal test adapter will damage the terminal. Refer to the J-35616 GM-Approved Terminal Test Kit label on the inside of the J-35616 GM-Approved Terminal Test Kit for the correct adapter along with the connector end view for terminal size.

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.

J 36169-A Fused Jumper Wire. See Special Tools and Equipment .

Using Fused Jumper Wires

The J 36169-A includes small clamp connectors that provide adaptation to most connectors without damage. See Special Tools and Equipment . This fused jumper wire is supplied with a 20-A fuse which may not be suitable for some circuits. Do not use a fuse with a higher rating than the fuse that protects the circuit being tested.

Measuring Voltage

Note. Do not insert test equipment probes (DVOM etc.) into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal will cause a poor connection, which will result in a system failure. Always use the J-35616 GM-Approved Terminal Test Kit or the J 42675 Flat-Wire Probe Adapter in order to front probe terminals. Do not use paper clips or other substitutes to probe terminals.When using the J-35616 GM-Approved Terminal Test Kit, ensure the terminal test adapter choice is the correct size for the connector terminal. Do not visually choose the terminal test adapter because some connector terminal cavities may appear larger than the actual terminal in the cavity. Using a larger terminal test adapter will damage the terminal. Refer to the J-35616 GM-Approved Terminal Test Kit label on the inside of the J-35616 GM-Approved Terminal Test Kit for the correct adapter along with the connector end view for terminal size.

The following procedure measures the voltage at a selected point in a circuit.

1. Disconnect the electrical harness connector for the circuit being tested, if necessary.
2. Enable the circuit and/or system being tested. Use the following methods: Turn ON the ignition, with the engine OFF. Turn ON the engine. Turn ON the circuit and/or system with a scan tool in Output Controls. Turn ON the switch for the circuit and/or system being tested.
3. Select the V (AC) or V (DC) position on the DMM.
4. Connect the positive lead of the DMM to the point of the circuit to be tested.
5. Connect the negative lead of the DMM to a good ground.
6. The DMM displays the voltage measured at that point.

Measuring Voltage Drop

Note. Do not insert test equipment probes (DVOM etc.) into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal will cause a poor connection, which will result in a system failure. Always use the J-35616 GM-Approved Terminal Test Kit or the J 42675 Flat-Wire Probe Adapter in order to front probe terminals. Do not use paper clips or other substitutes to probe terminals.When using the J-35616 GM-Approved Terminal Test Kit, ensure the terminal test adapter choice is the correct size for the connector terminal. Do not visually choose the terminal test adapter because some connector terminal cavities may appear larger than the actual terminal in the cavity. Using a larger terminal test adapter will damage the terminal. Refer to the J-35616 GM-Approved Terminal Test Kit label on the inside of the J-35616 GM-Approved Terminal Test Kit for the correct adapter along with the connector end view for terminal size.

The following procedure determines the difference in voltage potential between 2 points.

Scheme 24

1. Set the rotary dial of the DMM to the V (DC) position.
2. Connect the positive lead of the DMM to 1 point of the circuit to be tested.
3. Connect the negative lead of the DMM to the other point of the circuit.
4. Operate the circuit.
5. The DMM displays the difference in voltage between the 2 points.

Measuring Frequency

Note. Do not insert test equipment probes (DVOM etc.) into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal will cause a poor connection, which will result in a system failure. Always use the J-35616 GM-Approved Terminal Test Kit or the J 42675 Flat-Wire Probe Adapter in order to front probe terminals. Do not use paper clips or other substitutes to probe terminals.When using the J-35616 GM-Approved Terminal Test Kit, ensure the terminal test adapter choice is the correct size for the connector terminal. Do not visually choose the terminal test adapter because some connector terminal cavities may appear larger than the actual terminal in the cavity. Using a larger terminal test adapter will damage the terminal. Refer to the J-35616 GM-Approved Terminal Test Kit label on the inside of the J-35616 GM-Approved Terminal Test Kit for the correct adapter along with the connector end view for terminal size.

The following procedure determines the frequency of a signal.

1. Apply power to the circuit.
2. Set the rotary dial of the DMM to the V (AC) position.
3. Connect the positive lead of the DMM to the circuit to be tested.
4. Connect the negative lead of the DMM to a good ground.
5. Press the Hz button on the DMM.
6. The DMM will display the frequency measured.

Testing for Continuity

Note. Do not insert test equipment probes (DVOM etc.) into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal will cause a poor connection, which will result in a system failure. Always use the J-35616 GM-Approved Terminal Test Kit or the J 42675 Flat-Wire Probe Adapter in order to front probe terminals. Do not use paper clips or other substitutes to probe terminals.When using the J-35616 GM-Approved Terminal Test Kit, ensure the terminal test adapter choice is the correct size for the connector terminal. Do not visually choose the terminal test adapter because some connector terminal cavities may appear larger than the actual terminal in the cavity. Using a larger terminal test adapter will damage the terminal. Refer to the J-35616 GM-Approved Terminal Test Kit label on the inside of the J-35616 GM-Approved Terminal Test Kit for the correct adapter along with the connector end view for terminal size.

The following procedures verify good continuity in a circuit.

With a DMM

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.

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 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 Short to Ground

Note. Do not insert test equipment probes (DVOM etc.) into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal will cause a poor connection, which will result in a system failure. Always use the J-35616 GM-Approved Terminal Test Kit or the J 42675 Flat-Wire Probe Adapter in order to front probe terminals. Do not use paper clips or other substitutes to probe terminals.When using the J-35616 GM-Approved Terminal Test Kit, ensure the terminal test adapter choice is the correct size for the connector terminal. Do not visually choose the terminal test adapter because some connector terminal cavities may appear larger than the actual terminal in the cavity. Using a larger terminal test adapter will damage the terminal. Refer to the J-35616 GM-Approved Terminal Test Kit label on the inside of the J-35616 GM-Approved Terminal Test Kit for the correct adapter along with the connector end view for terminal size.

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

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.

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 a Short to Voltage

Note. Do not insert test equipment probes (DVOM etc.) into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal will cause a poor connection, which will result in a system failure. Always use the J-35616 GM-Approved Terminal Test Kit or the J 42675 Flat-Wire Probe Adapter in order to front probe terminals. Do not use paper clips or other substitutes to probe terminals.When using the J-35616 GM-Approved Terminal Test Kit, ensure the terminal test adapter choice is the correct size for the connector terminal. Do not visually choose the terminal test adapter because some connector terminal cavities may appear larger than the actual terminal in the cavity. Using a larger terminal test adapter will damage the terminal. Refer to the J-35616 GM-Approved Terminal Test Kit label on the inside of the J-35616 GM-Approved Terminal Test Kit for the correct adapter along with the connector end view for terminal size.

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.

Testing for Intermittent Conditions and Poor Connections

Tools Required

1. J 35616 GM-Approved Terminal Test Kit. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) .
2. J-38125 Terminal Repair Kit. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) .
3. J 42675 Flat-Wire Probe Adapter. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) .

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. Refer to «Inducing Intermittent Fault Conditions»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__inducing-intermittent-fault-conditions) in order to duplicate the conditions required in order to verify the complaint.
6. Refer to «Testing for Electrical Intermittents»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__testing-for-electrical-intermittents) for test procedures to detect intermittent open, high resistance, short to ground, and short to voltage conditions.
7. Refer to «Scan Tool Snapshot Procedure»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__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 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. See Special Tools and Equipment . 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 below to test terminal contact of Metri-Pack or 56 series terminals. Refer to the J-38125 or the J 38125-4 Instruction Manual for terminal identification. See Special Tools and Equipment .

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. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) . 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 J 42675 on the flat wire harness connector in order to test the circuit in question. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) .

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. Refer to Scan Tool Snapshot Procedure . You may need to load the vehicle in order to duplicate the concern. This may require the use of weights, floorjacks, 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 DMM set to Peak Min/Max mode and connected to the suspect circuit while testing can yield desirable results. Refer to 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

Tools Required

1. J 25070 Heat Gun. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) .

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»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__testing-for-short-to-ground)
2. «Testing for Continuity»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__testing-for-continuity)
3. «Testing for a Short to Voltage»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__testing-for-a-short-to-voltage)

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. Refer to «Troubleshooting with a Digital Multimeter»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__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.
4. Press the MIN MAX button of the J 39200 . The J 39200 displays 100 ms RECORD and emits an audible tone (beep). IMPORTANT: 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.
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. Refer to «Inducing Intermittent Fault Conditions»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__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.

Scan Tool Snapshot Procedure

Snapshot is a recording of what a control module on the vehicle was receiving for information while the snapshot is being made. A snapshot may be used to analyze the data during the time a vehicle condition is current. This allows you to concentrate on making the condition occur, rather than trying to view all the data in anticipation of the fault. The snapshot contains information around a trigger point that you have determined. Only a single data list may be recorded in each snapshot. The Scan Tool has the ability to store 2 snapshots. The ability to record 2 snapshots allows comparing hot versus cold and good versus bad vehicle scenarios. The snapshots are stored on a first-in, first-out basis. If a third snapshot is taken, the first snapshot stored in the memory will be lost.

Snapshots can be 1 of 2 types

1. Snapshot - taken from the Snapshot menu choice
2. Quick Snapshot - taken from the Data Display soft key choice, does not contain DTC information

When a snapshot is taken, it is recorded on the memory card and may contain as many as 1200 frames of information. Because the snapshot is recorded onto the memory card, snapshots are not lost if the Scan Tool is powered down.

The snapshot replay screen has a plot soft key that can be of great value for intermittent diagnosis. The snapshot plot feature can help you to quickly determine if a sensor is outside of its expected values by plotting 3 parameters at a time. The data will be displayed both graphically and numerically showing the minimum and maximum values for all frames captured. This is helpful, especially if the fault occurs only once and does not set a DTC.

Scheme 25

The fuse is the most common method of an automotive wiring circuit protection. Whenever there is an excessive amount of current flowing through a circuit the fusible element will melt and create an open or incomplete circuit. Fuses are an one time protection device and must be replaced each time the circuit is overloaded. To determine if a fuse is open, remove the suspected fuse and examine the element in the fuse for an open (2). If not broken (1), also check for continuity using a DMM or a continuity tester. If the element is open or continuity is suspect, replace the fuse with one of equal current rating.

Fuse Types

Circuit Protection - Circuit Breakers

A circuit breaker is a protective device that is designed to open the circuit when a current load is in excess of the rated breaker capacity. If there is a short or other type of overload condition in the circuit, the excessive current will open the circuit between the circuit breaker terminals. Two types of circuit breakers are used.

Circuit Protection - Fusible Links

Fusible link is wire designed to melt and break continuity when excessive current is applied. It is often located between or near the battery and starter or electrical center. Use a continuity tester or a DMM at each end of the wire containing the fusible link in order to determine if it is broken. If broken, it must be replaced with fusible link of the same gage size.

Repairing a Fusible Link

Refer to Splicing Copper Wire Using Splice Clips .

Wiring Repairs

The Wiring Repairs section contains the following types of wiring repair information. Using these elements together will make wiring repair faster and easier

1. «Circuit Protection - Fuses»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures)
2. «Circuit Protection - Circuit Breakers»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__circuit-protection-circuit-breakers)
3. «Circuit Protection - Fusible Links»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__circuit-protection-fusible-links)
4. «Repairing Damaged Wire Insulation»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__repairing-damaged-wire-insulation)
5. «Splicing Copper Wire Using Splice Clips»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__splicing-copper-wire-using-splice-clips)
6. «Splicing Copper Wire Using Splice Sleeves»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__splicing-copper-wire-using-splice-sleeves)
7. «Splicing Twisted or Shielded Cable»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__splicing-twisted-or-shielded-cable)
8. «Splicing Inline Harness Diodes»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__splicing-inline-harness-diodes)
9. «Heated Oxygen Sensor (HO2S) Wiring Repairs»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__heated-oxygen-sensor-ho2s-wiring-repairs)
10. «SIR/SRS Wiring Repairs»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__sirsrs-wiring-repairs)
11. «Flat Wire Repairs»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__flat-wire-repairs)

Repairing Damaged Wire Insulation

If the conductive portion of the wire is not damaged, locate the problem and apply tape around the wire. If the damage is more extensive, replace the faulty segment of the wire. Refer to Splicing Copper Wire Using Splice Clips and follow the instruction to repair the wire.

Wire Size Conversion

Flat Wire Repairs

Note. The flat wire within the flex wiring harness is not serviceable. If an open or short exists within the flex wiring harness the complete harness must be replaced.

J-38125 Terminal Repair Kit. See Special Tools and Equipment .

Heated Oxygen Sensor (HO2S) Wiring Repairs

Note. Do not solder repairs under any circumstances as this could result in the air reference being obstructed.

If the heated oxygen sensor pigtail wiring, connector, or terminal is damaged the entire oxygen sensor assembly must be replaced. Do not attempt to repair the wiring, connector, or terminals. In order for the sensor to function properly it must have a clean air reference. This clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degrade oxygen sensor performance.

The following guidelines should be used when servicing the heated oxygen sensor

1. Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor, causing poor performance. Also, the sensor pigtail and harness wires must not be damaged in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems.
2. Neither the sensor nor vehicle lead wires should be bent sharply or kinked. Sharp bends, kinks, etc., could block the reference air path through the lead wire.
3. Do not remove or defeat the oxygen sensor ground wire (where applicable). Vehicles that utilize the ground wire sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will also cause poor engine performance.
4. To prevent damage due to water intrusion, be sure that the peripheral seal remains intact on the vehicle harness connector.

The engine harness may be repaired using the J-38125 . See Special Tools and Equipment .

Splicing Copper Wire Using Splice Clips

J-38125 Terminal Repair Kit. See Special Tools and Equipment .

Scheme 26

1. Open the harness. If the harness is taped, remove the tape. To avoid wiring insulation damage, use a sewing ripper in order to cut open the harness. If the harness has a black plastic conduit, pull out the desired wire.
2. Cut the wire. Cut as little wire off the harness as possible. Ensure that each splice is at least 40 mm (1.5 in) away from other splices, harness branches and connectors. This helps prevent moisture from bridging adjacent splices and causing damage.
3. Select the proper size and type of wire. The wire must be of equal or greater size than the original (except fusible link). The wire's insulation must have the same or higher temperature rating. Use general purpose insulation for areas that are not subject to high temperatures. Use a cross-linked polyethylene insulated wire for areas where high temperatures are expected. IMPORTANT: Use cross-linked polyethylene wire to replace PVC, but do not replace cross-linked polyethylene with PVC. Cross-linked polyethylene wire is not fuel resistant. Do not use to replace wire where there is the possibility of fuel contact.
4. Strip the insulation. Select the correct size opening in the wire stripper or work down from the largest size. Strip approximately 7.5 mm (5/16 in) of insulation from each wire to be spliced.
5. Select the proper clip to secure the splice. Follow the instructions in the J-38125 in order to determine the proper clip size crimp tool and anvil. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) .
6. Overlap the 2 stripped wire ends and hold them between thumb and forefinger.
7. Center the splice clip (2) over the stripped wires (1) and hold the clip in place. Ensure that the wires extend beyond the clip in each direction. Ensure that no insulation is caught under the clip.
8. Center the crimp tool over the splice clip and wires.
9. Apply steady pressure until the crimp tool closes. Ensure that no strands of wire are cut.
10. Crimp the splice on each end (2).
11. Apply 60/40 rosin core solder to the opening in the back of the clip. Follow the manufacturer's instructions for the solder equipment.
12. Tape the splice. Roll on enough tape in order to duplicate the thickness of the insulation on the existing wires.
13. Additional tape can be applied to the wire if the wire does not belong in a conduit or another harness covering. Use a winding motion in order to cover the first piece of tape.

J-38125 Terminal Repair Kit. See Special Tools and Equipment .

Splicing Copper Wire Using Splice Sleeves

Use duraseal splice sleeves to form a one-to-one splice on all types of insulation except tefzel and coaxial. Use duraseal splice sleeves where there is special requirements such as moisture sealing. Follow the instructions below in order to splice copper wire using duraseal splice sleeves.

Splicing Copper Wire Using Splice Sleeves

Scheme 27

1. Open the harness. If the harness is taped, remove the tape. To avoid wiring insulation damage, use a sewing ripper in order to cut open the harness. If the harness has a black plastic conduit, pull out the desired wire.
2. Cut the wire. Cut as little wire off the harness as possible. Ensure that each splice is at least 40 mm (1.5 in) away from other splices, harness branches and connectors. This helps prevent moisture from bridging adjacent splices and causing damage.
3. Select the proper size and type of wire. The wire must be of equal or greater size than the original. The wires insulation must have the same or higher temperature rating (4). Use general purpose insulation for areas that are not subject to high temperatures. Use a cross-linked polyethylene insulated wire for areas where high temperatures are expected. IMPORTANT: Use cross-linked polyethylene wire to replace PVC, but do not replace cross-linked polyethylene with PVC. Cross-linked polyethylene wire is not fuel resistant. Do not use to replace wire where there is the possibility of fuel contact.
4. Strip the insulation. Select the correct size opening in the wire stripper or work down from the largest size. Strip approximately 7.5 mm (5/16 in) of insulation from each wire to be spliced (1).
5. Select the proper duraseal splice sleeve (2) and the required crimp nest tool, refer to the Crimp and Seal Splice Table.
6. Place the duraseal splice sleeve in the J-38125-8 (12085115) crimp tool nest so that the crimp falls at point 1 on the splice.
7. Close the hand crimper handles slightly in order to hold the duraseal splice sleeve firmly in the proper crimp tool nest.
8. Insert the wires into the duraseal splice sleeve until the wire hits the barrel stop. The splice sleeve has a stop in the middle of the barrel in order to prevent the wire from passing through the splice (3).
9. Close the handles of the J-38125-8 (12085115) until the crimper handles open when released. The crimper handles will not open until the proper amount of pressure is applied to the splice sleeve.
10. Shrink the insulation around the splice. Using the heat torch apply heat to the crimped area of the barrel. Gradually move the heat barrel to the open end of the tubing. The tubing will shrink completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinkage is achieved.

Splicing Twisted or Shielded Cable

Twisted/shielded cable is used in order to protect wiring from electrical noise. Two-conductor cable of this construction is used between the radio and the Delco-Bose® speaker/amplifier units and other applications where low level, sensitive signals must be carried. Follow the instructions below in order to repair the twisted/shielded cable.

Scheme 28

1. Remove the outer jacket (1). Use care not to cut into the drain wire of the mylar tape.
2. Unwrap the tape. Do not remove the tape. Use the tape in order to rewrap the twisted conductors after the splice is made.
3. Prepare the splice. Untwist the conductors and follow the splicing instructions for copper wire. Staggering the splices by 65 mm (2.5 in) is recommended.
4. Re-assemble the cable. Rewrap the conductors with the mylar tape. Use caution not to wrap the drain wire in the tape (1). Follow the splicing instructions for copper wire and splice the drain wire. Wrap the drain wire around the conductors and tape with mylar tape.
5. Tape over the entire cable. Use a winding motion when you apply the tape.

Splicing Inline Harness Diodes

Many vehicle electrical systems use a diode to isolate circuits and protect the components from voltage spikes. When installing a new diode use the following procedure.

1. Open the harness. If the harness is taped, remove the tape. To avoid wiring insulation damage, use a sewing ripper in order to cut open the harness. If the harness has a black plastic conduit, pull out the diode.
2. If the diode is taped to the harness, remove all of the tape.
3. Check and record the current flow direction and orientation of diode.
4. Remove the inoperative diode from the harness with a suitable soldering tool. IMPORTANT: If the diode is located next to a connector terminal remove the terminal(s) from the connector to prevent damage from the soldering tool.
5. Carefully strip away a section of insulation next to the old soldered portion of the wire(s). Do not remove any more than is needed to attach the new diode.
6. Check current flow direction of the new diode, being sure to install the diode with correct bias. Reference the appropriate service manual wiring schematic to obtain the correct diode installation position.
7. Attach the new diode to the wire(s) using 60/40 rosin core solder. Before soldering attach some heat sinks (aluminum alligator clips) across the diode wire ends to protect the diode from excessive heat. Follow the manufacturer's instruction for the soldering equipment.
8. Reinstall terminal(s) into the connector body if previously removed.
9. Tape the diode to the harness or connector using electrical tape.

SIR/SRS Wiring Repairs

Tools Required

1. J-38125 Terminal Repair Kit. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) .

The Supplemental Inflatable Restraint (SIR) System/Supplemental Restraint System (SRS) requires special wiring repair procedures due to the sensitive nature of the circuitry. Follow the specific procedures and instructions when working with the SIR/SRS system wiring, and the wiring components (such as connectors and terminals).

The tool kit J-38125 contains the following items: See Special Tools and Equipment .

1. Duraseal splice sleeves-In order to repair the SIR/SRS system wiring
2. A wire stripping tool
3. A special crimping tool
4. A heat torch
5. An instruction manual

The duraseal splice sleeves have the following 2 critical features

1. A special heat shrink sleeve environmentally seals the splice. The heat shrink sleeve contains a sealing adhesive inside.
2. A cross hatched (knurled) core crimp provides necessary contact integrity for the sensitive, low energy circuits.

The J-38125 also serves as a generic terminal repair kit. See Special Tools and Equipment . The kit contains the following items

1. A large sampling of common electrical terminals
2. The correct tools in order to attach the terminals to the wires
3. The correct tools in order to remove the terminals from the connectors

SIR/SRS Connector (Plastic Body and Terminal Metal Pin) Repair

Use the connector repair assembly packs in order to repair the damaged SIR/SRS wire harness connectors and the terminals. Do not use the connector repair assembly pack in order to repair the pigtails. These kits include an instruction sheet and the duraseal splice sleeves. Use the duraseal splice sleeves in order to splice the new wires, connectors, and terminals to the harness. The splice crimping tool is color keyed in order to match the splices from the J-38125 . See Special Tools and Equipment . You must use the splice crimping tool in order to apply these splices.

The terminals in the SIR/SRS system are made of a special metal. This metal provides the necessary contact integrity for the sensitive, low energy circuits. These terminals are only available in the connector repair assembly packs. Do not substitute any other terminals for those in the assembly packs.

If the individual terminals are damaged on the sensing and diagnostic module (SDM) harness connector, use one of the following 2 components in order to replace the SDM harness connector

1. The SDM harness connector pigtail assembly
2. The SDM harness connector replacement kit

If the individual terminals are damaged on any other SIR/SRS connection, use the appropriate connector repair assembly pack in order to replace the entire connection. Replace the entire SIR/SRS wiring harness, if needed, in order to maintain SIR/SRS circuit integrity.

SIR/SRS Wire Pigtail Repair

A wire pigtail is a wire or wires attached directly to the device (not by a connector). If a wiring pigtail is damaged, you must replace the entire component (with pigtail). The inflatable restraint steering wheel module coil is an example of a pigtail component.

SIR/SRS Wire Repair

If any wire except the pigtail is damaged, repair the wire by splicing in a new section of wire of the same gage size (0.5 mm, 0.8 mm, 1.0 mm etc.). Use the duraseal splice sleeves and splice crimping tool from the J-38125 . See Special Tools and Equipment . Use the following wiring repair procedures in order to ensure the integrity of the duraseal splice sleeves.

SIR/SRS Wiring Repairs

1. Open the harness by removing any tape: Use a sewing seam ripper (available from sewing supply stores) in order to cut open the harness in order to avoid wire insulation damage. Use the duraseal splice sleeves on all types of insulation except tefzel and coaxial. Do not use the crimp and duraseal splice sleeve to form a splice with more than 2 wires coming together.
2. Cut as little wire off the harness as possible. You may need the extra length of wire in order to change the location of a splice. Adjust splice locations so that each splice is at least 40 mm (1.5 in) away from the other splices, harness branches, or connectors.
3. Strip the insulation: When adding a length of wire to the existing harness, use the same size wire as the original wire. Perform one of the following items in order to find the correct wire size: Find the wire on the schematic and convert the metric size to the equivalent AWG size. Use an AWG wire gage. If you are unsure of the wire size, begin with the largest opening in the wire stripper and work down until achieving a clean strip of the insulation. Strip approximately 7.5 mm (0.313 in) of insulation from each wire to be spliced. Do not nick or cut any of the strands. Inspect the stripped wire for nicks or cut strands. If the wire is damaged, repeat this procedure after removing the damaged section.
4. Select the proper duraseal splice sleeve according to the wire size. Refer to the above table at the beginning of the repair procedure for the color coding of the duraseal splice sleeves and the crimp tool nests.
5. Use the Splice Crimp Tool from the J-38125 to crimp duraseal splice sleeve. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) . In order to position the duraseal splice sleeve in the proper color nest of the Splice Crimp Tool, refer to the table at the beginning of this repair procedure.
6. Place the duraseal splice sleeve in the nest. Ensure that the crimp falls midway between the end of the barrel and the stop. The sleeve has a stop (3) in the middle of the barrel (2) in order to prevent the wire (1) from going further. Close the hand crimper handles slightly in order to firmly hold the duraseal splice sleeve in the proper nest.
7. Insert the wire into the splice sleeve barrel until the wire hits the barrel stop.
8. Tightly close the handles of the crimp tool until the crimper handles open when released. The crimper handles will not open until you apply the proper amount of pressure to the duraseal splice sleeve. Repeat steps 4 and 5 for the opposite end of the splice.
9. Using the heat torch, apply heat to the crimped area of the barrel.
10. Gradually move the heat barrel to the open end of the tubing: The tubing will shrink completely as the heat is moved along the insulation. A small amount of sealant will come out of the end of the tubing when sufficient shrinkage is achieved.

SIR/SRS System Wire Splice Repair

Apply a new splice (not sealed) from the J-38125 if damage occurs to any of the original equipment splices (3 wires or more) in the SIR/SRS wiring harness. See Special Tools and Equipment . Carefully follow the instructions included in the kit for proper splice clip application.

Connector Position Assurance (CPA)

The connector position assurance (CPA) is a small plastic insert that fits through the locking tabs of all the SIR/SRS system electrical connectors. The CPA ensures that the connector halves cannot vibrate apart. You must have the CPA in place in order to ensure good contact between the SIR/SRS mating terminals.

Terminal Position Assurance (TPA)

The terminal position assurance (TPA) insert resembles the plastic combs used in the control module connectors. The TPA keeps the terminal securely seated in the connector body. Do not remove the TPA from the connector body unless you remove a terminal for replacement.

Connector Repairs

The Connector Repairs section contains the following types of connector repair information. Using these elements together will make connector repair faster and easier

1. «Connector Position Assurance Locks»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__connector-position-assurance-locks)
2. «Terminal Position Assurance Locks»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__terminal-position-assurance-locks)
3. «Push to Seat Connectors»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures)
4. «Pull to Seat Connectors»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures)
5. «Weather Pack Connectors»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__weather-pack-connectors)
6. «Repairing Connector Terminals»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__repairing-connector-terminals)

Connector Position Assurance Locks

The connector position assurance (CPA) is a small plastic insert that fits through the locking tabs of the connector. CPAs are used in various connectors throughout the vehicle. CPAs are also used in all SIR system electrical connectors. The CPA ensures that the connector halves cannot vibrate apart. You must have the CPA in place in order to ensure good contact between the mating terminals, of the connector.

Terminal Position Assurance Locks

The terminal position assurance (TPA) insert resembles the plastic combs used in the control module connectors. The TPA keeps the terminal securely seated in the connector body. Do not remove the TPA from the connector body unless you remove a terminal for replacement.

Terminal Removal

Follow the steps below in order to repair push to seat connectors.

1. Remove the terminal position assurance (TPA) device, the connector position assurance (CPA) device, and/or the secondary lock.
2. Separate the connector halves (1).
3. Use the proper pick or removal tool (1) in order to release the terminal.
4. Gently pull the cable and the terminal (2) out of the back of the connector.
5. Re-form the locking device if you are going to reuse the terminal (1).
6. To repair the terminal, refer to Terminal Repair.

Terminal Repair

1. Slip the cable seal away from the terminal.
2. Cut the wire as close to the terminal as possible.
3. Slip a new cable seal onto the wire.
4. Strip 5 mm (3/16 in) of insulation from the wire.
5. Crimp a new terminal to the wire.
6. Solder the crimp with rosin core solder.
7. Slide the cable seal toward the terminal.
8. Crimp the cable seal and the insulation.
9. If the connector is outside of the passenger compartment, apply grease to the connector.

Reinstalling Terminal

1. In order to reuse a terminal or lead assembly. Refer to «Wiring Repairs»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__wiring-repairs) .
2. Ensure that the cable seal is kept on the terminal side of the splice.
3. Insert the lead from the back until it catches.
4. Install the TPA, CPA and/or the secondary locks.

If the terminal is visibly damaged or is suspected of having a faulty connection, the terminal should be replaced.

Follow the steps below in order to repair pull-to-seat connectors

1. Remove the connector position assurance (CPA) device and/or the secondary lock.
2. Disconnect the connector from the component or separate the connectors for in-line connectors.
3. Remove the terminal position assurance (TPA) device.
4. Insert the proper pick or removal tool into the front of the connector body.
5. Grasp the wire at the back of the connector body and gently push the terminal (1) out the front of the connector body (3).

1. If the wire needed to be cut in order to remove the terminal, gently push a small length of the same size wire through the back of the connector cavity until there is enough wire exposed in order to crimp on a new terminal. If the wire was not cut, cut the existing wire as close to the old terminal as possible.
2. Strip 5 mm (3/16 in) of insulation from the wire.
3. Crimp a new terminal to the wire.
4. Solder the crimp with rosin core solder.

Terminal Installation

1. Align the terminal and pull the wire from the back of the connector in order to seat the terminal.
2. If necessary, cut the new wire to proper length and splice with existing circuit. Refer to «Splicing Copper Wire Using Splice Sleeves»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__splicing-copper-wire-using-splice-sleeves) .
3. If the connector is outside of the passenger compartment, apply dielectric grease to the connector.
4. Install the TPA, CPA and/or the secondary locks.

Weather Pack Connectors

The following is the proper procedure for the repair of Weather Pack® Connectors.

1. Separate the connector halves (1).
2. Open the secondary lock. A secondary lock aids in terminal retention and is usually molded to the connector (1).
3. Grasp the wire and push the terminal to the forward most position. Hold the wire in this position.
4. Insert the Weather Pack® terminal removal tool into the front (mating end) of the connector cavity until it rests on the cavity shoulder (1).
5. Gently pull on the wire to remove the terminal through the back of the connector (2). IMPORTANT: Never use force to remove a terminal from a connector.
6. Inspect the terminal and connector for damage. Repair as necessary. Refer to «Repairing Connector Terminals»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__repairing-connector-terminals) .
7. Reform the lock tang (2) and reset terminal in connector body.
8. Close secondary locks and join connector halves.
9. Verify that circuit is complete and working satisfactorily.
10. Perform system check.

Repairing Connector Terminals

Tools Required

1. J-38125 Terminal Repair Kit. See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) .

Use the following repair procedures in order to repair the following

1. Push to Seat terminals
2. Pull to Seat terminals

Some terminals do not require all of the steps shown. Skip the steps that do not apply for your terminal repair. The J-38125 contains further information. See Special Tools and Equipment .

1. Cut off the terminal between the core and the insulation crimp. Minimize any wire loss. For cable seal terminals, remove the seal.
2. Apply the correct cable seal per gage size of the wire, if used. Slide the seal back along the wire in order to enable insulation removal.
3. Remove the insulation.
4. For sealed terminals only, align the seal with the end of the cable insulation.
5. Position the strip in the terminal. For sealed terminals, position the strip and seal in the terminal.
6. Hand crimp the core wings.
7. Hand crimp the insulation wings. For sealed terminals, hand crimp the insulation wings around the seal and the cable.
8. Solder all of the hand crimp terminals excepting Micro-Pack 100 .64 size. Soldering Micro-Pack 100 World terminals may damage the terminal.

Power and Grounding Schematic Icons

Power and Grounding Schematic Icons Icon Icon Definition CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR Disabling and Enabling Zones . Failure to observe the correct procedure could cause deployment of the SIR components, personal injury, or unnecessary SIR system repairs

Power Distribution Schematics

For power distribution schematics refer to appropriate System Wiring Diagrams article.

Ground Distribution Schematics

For ground distribution schematics refer to appropriate System Wiring Diagrams article.

Upfitter Provision Schematics

For upfitter provision schematics refer to appropriate System Wiring Diagrams article.

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J 43244 Relay Puller Pliers. See Special Tools and Equipment .

Removal Procedure

1. Remove the electrical center cover.
2. Locate the relay. Refer to «Electrical Center Identification Views»(/chevrolet/chevy-express-g3500/1996-2012/remont/electrical-component-locations/#wiring-systems-component-locator) to locate the electrical center where the relay exists.
3. Using the J 43244 (1) position the tool on opposing corners of the relay (2). See «Special Tools and Equipment»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures) .
4. Remove the relay (2) from the electrical center.

Installation Procedure

1. Install the relay (2) in the same position as removed.
2. Install the electrical center cover.

1. Locate the relay. Refer to the «Master Electrical Component List»(/chevrolet/chevy-express-g3500/1996-2012/remont/electrical-component-locations/#wiring-systems-component-locator__master-electrical-component-list) to locate the relay in the vehicle.
2. Remove any fasteners which hold the relay in place.
3. Remove any connector position assurance (CPA) devices or secondary locks.
4. Separate the relay (1) from the wire harness connector (2).

1. Connect the relay (1) to the wire harness connector (2).
2. Install any connector position assurance (CPA) devices or secondary locks.
3. Install the relay using any fasteners or tape that originally held the relay in place.

1. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure»(/chevrolet/chevy-express-g3500/1996-2012/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
2. Press tabs (3) inward to lift and remove the junction block cover (1).
3. Note location and remove harness end nuts (2) and remove harness ends from fuse block relay center.
4. Remove the fuse block center bolts and remove fuse relay center from the junction block.
5. Remove from the junction block base the Chassis Harness (1), the I/P Harness (2), the Engine Harness (3), and the Forward LP Harness (4).
6. Remove the junction block base by pressing tabs (1) then slide tabs (2) out.

1. Install the junction block base by sliding tabs (2) in and pressing in tabs (1) until they are locked.
2. Install into the junction block base the Chassis Harness (1), the I/P Harness (2), the Engine Harness (3), and the Forward LP Harness (4).
3. Install the fuse relay center into the junction block.
4. Install the fuse block center bolts.
5. Install the harness ends on the fuse block relay center.
6. Install the harness end nuts (2).
7. Install the junction block cover (1) the tabs (3) should lock.
8. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure»(/chevrolet/chevy-express-g3500/1996-2012/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.

1. Disconnect the battery negative cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure»(/chevrolet/chevy-express-g3500/1996-2012/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.
2. Remove the drivers seat. Refer to «Seat Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/seats/#seat-system) in Seats.
3. Remove the junction block cover (1).
4. Remove the positive battery cable nut (2) from the junction block.
5. Remove the positive battery cable (3) from the junction block.
6. Disconnect the electrical connectors (1) from the junction block, if equipped with YF7.
7. Completely loosen the junction block caged bolts (2).
8. Release the tabs that retain the junction block (1) to the junction block base.
9. Remove the junction block (1) from the block base.
10. Remove the junction block base nuts (1, 3).
11. Remove the wiring harness (4) from the junction block base (2).
12. Remove the junction block base (4) from the floor.

1. Install the wiring harness (2) to the junction block base (3).
2. Install the junction block base (3) to the floor studs. Ensure the remaining electrical connections (4, 5) are not captured under the junction block base after installations the floor studs.
3. Install the junction block base nuts (1) to the floor studs. Tighten: Tighten the block base nuts to 5 N.m (44 lb in).
4. Install the junction block (1) to the junction block base. Ensure the retaining tabs are fully seated. Tighten: Tighten the bolts (2) to 5 N.m (44 lb in).
5. Connect the electrical connectors (1), if equipped with YF7.
6. Connect the positive battery cable (3) to the junction block.
7. Install the positive battery cable nut (2). Tighten: Tighten the nut (2) to 10 N.m (88 lb in).
8. Install the junction block cover (1).
9. Install the drivers seat. Refer to «Seat Replacement»(/chevrolet/chevy-express-g3500/1996-2012/remont/seats/#seat-system) in Seats.
10. Connect the battery negative cable. Refer to «Battery Negative Cable Disconnect/Connect Procedure»(/chevrolet/chevy-express-g3500/1996-2012/remont/charging-system/#battery-charging-system-and-starting-system) in Engine Electrical.

Special Tools

Special Tools Illustration Tool Number / Description J 25070 Heat Gun 500-700 F J 35616 GM Terminal Test Kit J 35616-200 Test Light - Probe Kit J 36169-A Fused Jumper Wire J 38125 Terminal Repair Kit J 38125-5 Ultra Torch J 39200 Digital Multimeter J 42675 Flat-Wire Probe Adapter J 43244 Relay Puller Pliers

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See also:
• SIR Caution
• Electrical Center Identification Views
• Master Electrical Component List
• Battery Negative Cable Disconnect/Connect Procedure
• Seat Replacement
• Fastener Notice
• Using Connector Test Adapters
• Probing Electrical Connectors
• Troubleshooting with a Digital Multimeter
• Troubleshooting with a Test Lamp
• Using Fused Jumper Wires
• Measuring Voltage
• Measuring Voltage Drop
• Measuring Frequency
• Testing for Continuity
• Testing for Short to Ground
• Testing for a Short to Voltage
• Special Tools and Equipment
• Inducing Intermittent Fault Conditions
• Testing for Electrical Intermittents
• Scan Tool Snapshot Procedure
• Splicing Copper Wire Using Splice Clips
• Circuit Protection - Circuit Breakers
• Circuit Protection - Fusible Links
• Repairing Damaged Wire Insulation
• Splicing Copper Wire Using Splice Sleeves
• Splicing Twisted or Shielded Cable
• Splicing Inline Harness Diodes
• Heated Oxygen Sensor (HO2S) Wiring Repairs
• SIR/SRS Wiring Repairs
• Flat Wire Repairs
• Wiring Repairs
• Connector Position Assurance Locks
• Terminal Position Assurance Locks
• Weather Pack Connectors
• Repairing Connector Terminals