Troubleshooting Tests

PROBING
After probing, when reconnecting connectors or replacing terminals, always be sure to reinstall Connector Position Assurance (CPA) and Terminal Position Assurance (TPA).

Frontprobe
When frontprobing of connectors is required, always use a mating terminal adapter (GM Connector Test Adapter Kit J 35616 or equivalent). The use of proper adaptors will ensure that proper terminal contact integrity is maintained.

Backprobe
Only backprobe connector terminals when specifically called for in diagnostic procedures. Since backprobing can be a source of damage to connector terminals, extra care must be taken to avoid deforming the terminal, either by forcing the test probe too far into the cavity or by using too large a test probe.

After backprobing any connector, always check for terminal damage. If terminal damage is suspected, check for proper terminal contact, refer to Checking Terminal Contact. Checking Terminal Contact

Voltage Check:

TESTING FOR VOLTAGE
1. Connect one lead of a test light to a known good ground. When using a voltmeter, be sure the voltmeter's negative lead is connected to ground.
2. Connect the other lead of the test light or voltmeter to a selected test point (connector or terminal).
3. If the test light illuminates, there is voltage present. When using a voltmeter, note the voltage reading.

Continuity Check through a Switch:

TESTING FOR CONTINUITY
1. Remove the fuse to the circuit involved.
2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test.
3. Connect the other lead to the other end of the circuit.
4. If the self-powered test light glows, there is continuity. When using an ohmmeter, low or no resistance means good continuity.

Voltage Drop Test:

TESTING FOR VOLTAGE DROP
This test checks for voltage being lost along a wire, or through a connection or switch.
1. Connect the positive lead of a voltmeter to the end of the wire (or to one side of the connection or switch) which is closer to the Battery.
2. Connect the negative lead to the other end of the wire (or the other side of the connection or switch).
3. Operate the circuit.
4. The voltmeter will show the difference in voltage between the two points.

Testing for Short with Test Light or Voltmeter:

TESTING FOR SHORT TO GROUND

With a Test Light or Voltmeter
1. Remove the blown fuse and disconnect the load.
2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered).
3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the test light or voltmeter.
4. When the test light glows, or the voltmeter registers, there is a short to ground in the wiring near that point.

Testing for Short with Self-Powered Test Light or Ohmmeter:

With a Self-Powered Test Light or Ohmmeter
1. Remove the blown fuse and disconnect the Battery and load.
2. Connect one lead of a self-powered test light or ohmmeter to the fuse terminal on the load side.
3. Connect the other lead to a known good ground.
4. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the self-powered test light or ohmmeter.
5. When the self-powered test light glows, or the ohmmeter registers, there is a short to ground in the wiring near that point.

Fuses Powering Several Loads
1. Find the schematic for the fuse that has blown.
2. Open the first connector or switch leading from the fuse to each load.
3. Replace the fuse.
^ If the fuse blows, the short is in the wiring leading to the first connector or switch. Use a test light or meter as described previously.
^ If fuse does not blow, refer to next step.

4. Close each connector or switch until the fuse blows in order to find which circuit the short is in. Connect test lamp or meter at the connector to the suspect circuit (disconnected) rather than at the fuse terminals.