General Electrical Diagnosis Procedures

Trouble Shooting Guides

Notice

When troubleshooting an electrical system, make sure there are no electrical loads ON, except for the circuits or system being tested. This will help prevent false readings and the chance of a dead battery. After the car has been serviced, always visually inspect the battery to be sure the Green Eye is visible in the battery hydrometer.

Before Trouble Shooting

Visually inspect the wires and the connectors.
Verify that the terminal pins are clean and that there are no loose pins or terminals.
Verify that the Weather-Pac connectors are in good condition and sealed properly.
Check the minifuse, maxifuse or circuit breaker used to protect the circuit or system being tested.
Check the battery for damage, state of charge, and for clean and tight connections.
Check the accessory drive belt.

Five-Step Trouble Shooting

Verify the complaint.

Perform the System Performance Test, if the section has one outlined at the beginning of the section.
Learn more about the nature and location of the problem. Use the general description to learn how the circuit operates, when the circuit should operate, and how the components interact to make the circuit complete.
Analyze what parts of the system are working.
Do not fix only part of the problem.
Do not begin disassembly or testing until you have narrowed down the possible causes.

Analyze the electrical schematic and consult the flowcharts for the system being tested.

Look at the electrical schematic for the problem circuit. Determine how the circuit is supposed to work and look for minifuses, maxifuses, circuit breakers, wires, and grounds that are shared with other systems or components. See if a shared wire is at fault by checking other components fed by the wire. If several circuits fail at the same time, check for a common voltage or ground connection. If part of a circuit fails, check the connections between the part that works and the part that does not work.
Follow the flowcharts to find the possible cause(s) of the problem.
Based on the symptoms and your understanding of the circuit operation, identify one or more possible causes of the problem.
Refer to the component location diagram for the system to help locate the component and/or connector while diagnosing.

Isolate the problem by testing the circuit. Use diagnostic service probes as needed on 0.35, 0.50, and 0.80 2 mm (22, 20, and 18 gage) wires.

Perform circuit tests to check the diagnosis made in step two. You can either test for the most likely cause of failure first, or perform tests which are most easily and quickly done.
Generally, fuses and grounds are easiest to check.

Fix the problem.

Once the problem is identified, make the repair.
Make sure to use the proper tools and safe methods mentioned in the Vehicle Electrical Diagnostics.

Make sure the circuit works.

Operate all components in the repaired circuit in all modes of operation and verify that the repair has removed all the symptoms.
Make sure no new problems have come up and that the original problem has been fixed.

Helpful Hints

If a fuse is blown, look for a short to ground in the circuits between the fuse block and the component or for a short internal to the component. The short may also be in a circuit that is switched, such as a circuit beyond a relay contact.
Before checking the integrity of a circuit by means of a voltmeter or ohmmeter, check to see if other components or systems fed or grounded by the circuit are operating properly.
Verify that the connector pin terminals are not spread apart, broken, worn, or corroded due to salt water, antifreeze, etc.
Verify that the terminals and the pins are in their correct cavities.
Opens normally occur at connectors, terminals, and splices.
Use a diagnostic service probe and a multimeter to diagnose circuits that contain 0.35, 0.50, and 0.80 2 mm (22, 20, and 18 gage) wires. The diagnostic service probe causes a minimum of disturbance to the circuit wiring and connections.