Working through complex problems on today's complex vehicles

When a vehicle comes into your shop today, you need to be on the top of your game. Let’s face it: Today’s vehicles are a lot more complex than those of even 10 years ago. Vehicles 10 years ago were considered very complex compared to the 10 years prior to that. 

Now to get to my point: When one of these vehicles comes to your shop, it could be for something as simple as a routine brake job or as complex as a Controller Area Network (CAN) communication problem. Regardless of the problem, you have to have several tools in place to repair these issues.

1. You need to understand how the system you are taking on works. And to do that, you need a good service information system. It is plain suicide to attempt to work on a vehicle today without one.

2. You need to use a capable and up-to-date scan tool. If you’re asking yourself, “Do I really need a scan tool to do a brake job on a vehicle?” the answer is absolutely — for that, and for many other so-called “routine” services! You might need to use your scan tool to bleed the brake system or release the calipers so you can install those brake pads. That’s part of the complexity of today’s high tech vehicles: Without the proper tooling, you’re not repairing the vehicle correctly. 

3. You need to use a good digital multimeter (DMM). The days of using your test light to check a circuit on a computer that’s only supposed to put out 5 volts is long gone. Don’t get me wrong, a test light is still a valuable tool; but now the use of it needs to be considered carefully before relying on it to diagnose a particular circuit. 

Now that you have a working knowledge of the system, all the correct tooling and an accurate service information system, fixing these vehicles should be a snap, right? Not so fast. Now the fun really begins!

As a mobile tech, I get calls that are sometimes easy, cut-and-dry jobs — or so they seem. Then there are some that will fight me tooth and nail. The ones that should be easy sometimes turn into the tough ones because one of the three tools previously discussed, for lack of a better term, aren’t working as designed. 

Agree to Disagree
On one particular job, a shop called me in for a 2001 Hyundai Elantra with a 2.0L four-cylinder, automatic transmission, showing 106,000 miles on the odometer. The complaint was a check engine light on and a stalling condition. 

I grabbed one of my scan tools and proceeded to hook up to this car and pull the codes. Stored in the Engine Control Module (ECM) were codes P1515 (Oil Temperature Sensor Abnormal) and P1516 (Oil Temperature Sensor Low). I went to my service information (SI) system and pulled up the code definitions so I could see how these codes are deciphered for this specific vehicle. According to the SI, the codes were tied to the Idle Speed Control (ISC) actuator circuit. 

So which one do you believe? Is the scan tool wrong? Or is the information system not giving the correct description? How do you decide? What if you only have one information system and access to only one scan tool? Many shops have access to more than one scan tool and or information system. If you happen to work at one of them, you’re lucky. If not, then your job just got a lot harder. Remember, you only have a certain amount of time to diagnose this vehicle. 

This is what makes the job of an auto technician more challenging — and it’s the reason why some of us have more hair left on our heads than others. Fixing today’s vehicles isn’t always cut and dry. You may think that you have all of the correct information and tools needed to do the job, but then you find out that you don’t.

Luckily, I happened to have another scan tool to try. I hooked up the second tool to this car and got a completely different code description compared to the first scan tool, and one that agreed with my SI code descriptions. So I dove into it some more and looked for a component locator in the information system I was using. 

I went to the car — and the component wasn’t where the information system said it should be. Fortunately, I had another information system to which I could compare the data. The second SI source proved to be more accurate. This kind of stuff is what makes a simple diagnostic turn into a head scratcher. 

Fortunately, when you come across a discrepancy in the information that you find to be incorrect, there usually is a number you can call and report it. When they release the next upgrade, then, the fix should be included with the new software. Hopefully your call will prevent this from happening to the next tech who comes across this problem. 

On this vehicle, the information system I used to get the code description had the incorrect location of the idle speed actuator. The second information system did have the correct location. Having multiple resources at your disposal is essential in fixing vehicles today. Pulling every available resource that you can obtain will not only speed up your diagnosis, but it will make your diagnosis more accurate. After finishing my diagnosis, this car was repaired by replacing the ISC.

To Hold, or Not to Hold
A different shop called me in to look at a vehicle that had an issue with the battery not holding a charge. This vehicle was a 2006 Chrysler Town and Country with the 3.3L V-6, automatic transmission with 98,000 miles on the odometer. The complaint with this vehicle was that after a couple of days of sitting, the car wouldn’t start and the battery would be dead. 

One of the first things I personally like to do is check the state of charge by doing a quick charge check. I start the vehicle and attach my test leads to the battery terminals while the vehicle is running, so I can get a “somewhat sorta” idea of the condition of the battery and charging system. This is by no means the absolute correct way to check an electrical system, but it is a way of getting a quick idea of what you’re working with. 

Because the customer complaint was that the battery goes dead after a few days of sitting, I knew from experience that there is probably a parasitic draw in the system. I started my test by setting up my tool to the voltmeter setting and attaching my test leads to both battery connections while the car was running at an idle. The 16.75-volt reading I got certainly caused my eyebrows to raise!

I checked the dash for any indicator lights that might be on, but no lights were lit. Judging by my readings, it seemed the vehicle was overcharging. 

I connected to the Diagnostic Link Connector (DLC) to see whether there were any codes listed for an overvoltage or overcharge condition. There were no codes stored in either current status or in history, which seemed really odd to me. 

The next thing I did was a visual inspection of the battery to see whether it was bulging on the sides of the case, as that usually means the battery has been overcharged. The battery looked good with no signs of distress. 

Being the skeptic that I am, I grabbed another meter from my tool arsenal to see whether the reading I was getting was the same as the reading I obtained from the first tool. Once again, the reading was completely different. In fact, it was a 2.5-volt difference. In today’s world of high-tech, computer-controlled vehicles, that much of a difference is enough to affect the way a vehicle operates. 

With these two readings, which one should I go with? The first tool is significantly more expensive and more sophisticated than the second tool. The second tool is much older and slower, so my guess would be the first tool gave the correct reading, right? Wrong! The second tool was actually correct. 

The first tool will have to be sent out to the service center for repair. After confirming that the battery and charging system were working as they should, I proceeded with the diagnosis of the parasitic drain.

These two case studies bring to the forefront what can happen when a diagnostic problem that should be cut and dry is not. We rely on our tools, our information, our experience and our diagnostic thought process to be able to fix today’s vehicles quickly and accurately. It’s frustrating when we do not have the right information, or our tools provide misleading information when we try to do our jobs.

We pride ourselves on solving problems — repairing the vehicles that nobody else can repair. If you are part of that elite group with motor oil running through your veins, and you have that passion to be the best of the best, then I applaud you. This is not an easy business to be in, but it can be a satisfying one. 

Never rely on what is presented, but always rely on yourself and your knowledge. If something doesn’t seem right to you, check and recheck it again.  This will make you a better technician in the long run. 

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