Electrical Car Repair

Electrical problems can be difficult

Electrical problems can be one of the more difficult problems for an automotive repair shop solve. Frequently, electrical problems will be intermittent, and if the circuit is working during testing, it can’t be diagnosed. It can be difficult to come up with an effective diagnostic strategy when the problem is playing hide and seek, even when the working with a simple circuit. Newer cars seldom have simple circuits though. They have more electronic systems and devices than ever before, and the more complex and interconnected systems there are, the greater the challenges.

While correctly finding and repairing electrical problems can be difficult, we are uniquely qualified to diagnose the problem and repair it correctly the first time. Why? There are several reasons:


We specialize. We work on only five makes of cars. What’s so great about that? For one, we’re familiar with the systems. The first thing a mechanic does before touching a single tool, is find out how the system is supposed to work. If you don’t know how it should work, you certainly can’t tell if it’s not working correctly.

Familiarity means more than just knowing how a system functions. It means we may already know how a particular sensor or actuator circuit works, because we’ve worked on the same one before. We may be able to save time on reading descriptions and diagrams.

Finally, we may have seen the same problem before. A quick verification of the what we think the problem is, and we save a huge amount of time. Why should you care how long it takes us to find the problem? Because you’re paying us by the hour!

EXPERIENCE with electrical car repairs

“They’re a bunch of gray hairs”. In the trades, this is both a compliment and and insult. We’re not lifting engine blocks like we once did, but we sure do know a lot more than we did back in our “prime”. The best way to learn something, and remember it forever, is to screw up. We’ve been doing this so long, we might have already made every mistake there is, and as a result, we’ve figured out how to do diagnostic work quickly and efficiently without messing up.

There’s nothing wrong with learning. Everyone’s got to do it before they can move on to “knowing”. And as an industry, we really need fresh blood since the 18-25 demographic accounts for only 2% of the automotive technicians currently working. That said, would you rather pay someone hourly who’s at the top of their game, or someone who’s still figuring things out?


Electrical diagnosis and repair used to be a mostly analog game. Voltages between 0V and 14.5V that we’d measure with a voltmeter. High tech stuff back in the 80s. We’d use a fancy voltmeter with a swinging needle, not a cheap test light like those other guys.

Electrical car repair is seldom analog these days. Now everything’s digital. Zeros and ones, each represented by a number of different voltages, all depending on the what the engineers decide the the best bang for the buck this week. The primary tool for digital diagnosis is the factory scan tool. I mean you can look at the zeros and ones with an oscilloscope, but you really can’t say much more than they exist at the point where you’re measuring them. What are they saying? I don’t know. That’s what the scan tool is for.

In case you’re thinking that a scan tool is just for powertrain diagnostic work, it’s not. Your horn, wipers, brake lights, climate control, windows — blah, blah, blah, you get the idea. Just about everything electrical is controlled by a node somewhere on the network. It’s called multiplexing and it saves weight and money on wires. Besides, the pure volume of electrical stuff on modern cars wouldn’t be possible without it.

Electrical car repairs are a whole lot easier with an OE scan tool. We have a factory scan tool for every make we repair. Trying to diagnose a car without one is possible, sometimes. However, diagnosis is billed by the hour and going to a shop with the right tools will save you money.


Imagine looking up a wiring diagram. You find the cam actuator solenoid is grounded with a duty cycle provided by the ECM. You check the blue and white wire at connector C23 and find no signal. Aha! A bad ECM! You replace the ECM and the car still doesn’t work. Well you know what “new” stands for right? Never Ever Worked! It was bad out of the box, the mantra of the incompetent (well at least 99.9% of the time) mechanic. Order a new ECM. Car’s still broken. Time for a 3rd computer?

Correct information is critical when diagnosing a car. The best diagnostic technician in the word will have a very hard time without diagrams and descriptions. Modern cars typically have 20-40 control units networked together, hundreds of sensors, and thousands of individual electrical terminals. Without a map, we’d be lost. That’s why we subscribe to the same information services the dealerships use.


Does it cost a lot? Yes, but not as much as being in the dark. By the way, if you’re a do-it-yourself’er, you can subscribe for a single day to any of the techinfo sites.

A Few Electrical car repairs we’ve done here

Highlander inverter repair

Prius multi-display

Honda encoder fault

Lexus P0AA6 fault

Predictive battery failure analysis