How to Troubleshoot Toyota Electrical Systems
The electrical system on a Toyota can be checked using a voltmeter. All Toyotas use a simple "power and ground" system -- meaning that there are two, and only two, leads in all of the electrical components: the power lead and the ground lead. This makes troubleshooting the electrical system easier than troubleshooting most other types of electrical system (such as a house).
Remove the fuse panel cover by pulling it down. The fuse panel cover is usually located under the steering wheel.
Look on the underside of the cover for the diagram. This diagram tells you where all of the fuses are in the fuse box.
Remove each fuse -- one at a time -- with the fuse puller that is in the fuse panel and check to make sure that the metal strip inside each fuse is intact. If any fuses are burnt or damaged, replace them with a fuse of the same amperage. Because all of the major electrical components use fuses, an electrical problem can usually be traced through the fuse box. If a fuse keeps blowing out, there may be a problem with the component or a short in the wiring somewhere.
Open the hood of the Toyota. Turn the dial on the voltmeter to "volts." Touch the red lead on the voltmeter to the positive terminal on the battery. Touch the black lead on the voltmeter to the negative terminal on the battery.
Check the voltage. It should read 12.6 volts. If it does not, your battery has failed and must be replaced.