All experienced driveability and diagnostic technicians have seen their fair share of mistakes. It’s all part of the learning process. In fact, in my opinion…if you are not making mistakes, you aren’t pushing yourself to step outside of your comfort zone and learn something new.
The difference between myself and some of my peers that I grew up alongside of in this industry is that I leveraged my mistakes as an opportunity to improve. This came in the form of brutally honest personal reflection and thorough documentation of the entire experience — not only in what I found wrong with the vehicle but the steps I took to get there. Some of them were wise, many were not. But the fact is I learned, and so can you. Check out the method to my madness.
The Innocence of Youth
I’ll begin with my very first mobile diagnostic job in the winter months of 2008. I had just begun working outside of the OE environment of the dealership and broadening my horizons. Some may say I was crazy for doing that because I was doing well at the dealership (and not yet well on other makes and models). But I was bored and needed more. It was rarely easy but I’m so glad I made that change.
I was faced with a phone call from my (now) good buddy, John. He owned a transmission specialty shop just outside of Philadelphia. John is a very capable technician but simply lacked the time to involve himself with troublesome diagnostic challenges outside his realm of transmissions.
John told me he had in his possession a 1988 supercharged Ford Thunderbird with the complaint of an intermittent stall. John then asked if I was willing to come down and look at the issue for him (I sure as heck wasn’t going to say “no.”)
I made the 75-mile drive and was faced with the Thunderbird. It started without hesitation and with no warning lamps illuminated so I proceeded to drive the vehicle for well over an hour before it stalled for me. Full of excitement (but also anxiety, as I was on the side of the road more than 5 miles from the comfort of the shop, and supervision), I turned the key and expected some signs of trouble. However, to my surprise, the engine fired up without hesitation and I continued my drive. This time, I drove six hours without even a sign of stalling in sight. The end of the day was near and I made my way back to the shop with my tail between my legs. Thoughts ran through my head:
- How will I explain eight hours of invested time to John — and without a resolution?
- How can I expect to get paid for my time if I hadn’t accomplished anything?
- Am I paying to fill the tank of this gas-guzzler?
- Will John send me packing or worse — will he expect me to stay the course?
All of these questions made me uncomfortable and for the first time, I felt unsure of myself and my future as a diagnostician. To my surprise, John was not upset when I told him. He, in fact, wanted me to keep trying. “Next weekend it will be here for you, Brandon” is the last thing he said to me that day. The real kicker is, when I moved the vehicle into the shop for security purposes, it stalled on me. (And yes, I was almost in tears as it was now closing-time.)
The following Saturday I made another 150-mile round trip to take another stab at the elusive fault — this time with a fresh attitude and confidence. I drove the vehicle for two hours before it stalled. Although I was timid and already frustrated, I kept at it. I was only a block from the shop so I started the engine, and beat-feet back to the shop.
Once there I decided to capture fuel pump current. (Why? It was a test I learned to do from Jim Linder and it looked cool.) The results showed a flawlessly operating DC motor (Figure 2). It didn’t bring me any closer to fixing the car but at least I proved something was not broken or suspect.
I was at a loss. I wasn’t sure where to go from here and I was too embarrassed to ask for input. At this point at least no one knew I was clueless. I figured I’d just fake it until I made it.
The day came and went and I was nearing the second weekend (nearly 16 hours invested) and nothing to show for it except for another empty gas tank and a flawless fuel pump current ramp capture. It was at that point I pulled the car back in the shop at closing-time.
As I did, it stalled again! Now, I was getting excited because both times the car entered the shop, the stall occurred. Could this be a clue?
A Shot at Redemption
John witnessed my conviction and excitement and agreed to stay late while I attempted to throw a net over this Thunderbird. What I noticed about the stall is that it occurred only in a specific work bay (the alignment bay, with the ramps). As I hit the base of the ramps the stall occurred.
I decided to take the vehicle on the road and retrace my steps to repeat the road test, specifically where I remember the stall occurring. Each time the stall occurred I noticed there was a nasty pothole present. I decided to deliberately aim for the speed bump in a nearby parking lot and, as if I knew what I was doing, I was able to repeat the stall, seemingly at will.
I returned to the shop and opened the hood with the intention of testing circuits related to the ignition coil control module (like the ignition coil, the CKP sensor, CMP sensor, etc.). I figured if it was a fueling issue, it wouldn’t have stalled as suddenly and certainly wouldn’t have restarted flawlessly. Now, I was getting somewhere.
As I prepared to infiltrate the circuits, something at the ignition control module caught my eye. It was a poorly fitted cable tie used to mate the wire harness to the ignition control module. The connector assurance tab was broken (Figure 3). I thought there was no way it could be this obvious. I touched the connector and the engine stalled. I chanted with excitement!
With great pride I expressed my hard work and diligence to John. I demonstrated the fault for him and he compensated me for my time. He said he would have his tech splice in a new connector and assured me he would be calling me next time he needed my services.
The Long Ride Home
With a huge smile on my face, I still faced a 90-minute ride home but it gave me time to reflect on my 16-hour saga. I was proud of myself for sticking it out and not quitting but now it was time to face the fact that it was ugly.
I needed to make some changes but what, and how? What could I have done differently to make this job go smoother? It wasn’t my fault the car took eight hours to stall, and I couldn't change the fact the car yielded very little diagnostic data to be ascertained from a scan tool.
I’m sure you realize I’m jokingly and deliberately making poor excuses that we’ve all heard, or maybe even said. I realized there had to be a better way, but the only way I would be able to discover that was to take responsibility for my actions and my lack of structured diagnostic approach. I would wait to get home because I had ideas I needed to get on paper.
As I sat at my dining room table and placed my ideas down on paper, it all came out in paragraph format, like a journal entry. Things like “If I didn’t see this through visual inspection, how could I have tested for it?” With the tools I had at that time, there certainly wasn’t a test that would show the fault — and the results would have pointed to a faulty ignition control module as the signal would have always remained present on the suspect circuit(s).
Obviously, replacing the module would have been a bad mistake. But, with the flawless signals (and 20/20 hindsight vision) logic would now have me inspect the connector integrity before condemning the ICM. Why? Because we can’t test inside the connector, we can only eliminate everything else (Figure 4).
This journal entry also included some bullet points describing what data I took note of and the description of the experience overall. It was only after I had read what I wrote that I realized this would be my secret weapon in powerful diagnostics.
The journal entry showed all the holes in my approach, and also told me what I should do differently if I was presented this same opportunity again.
With that, I realized if I had asked just a few questions ahead of time, I would most certainly have saved myself about 15 hours of time. These could have been questions to ask the shop owner, or better yet, the client.
- Where were you driving when the car last stalled?
- Have you ever been able to reproduce the stall on the same road?
- When the stall occurs, is it typically on bumpy roads?
- Do weather conditions play a role?
- When did this problem start?
Those are just a few ideas that come to mind. And to be honest, when I later spoke with the customer he indeed indicated — but only when asked — that the stall occurred mostly on rough roads. If I had asked that question up front, I could have cut down my time spent on the road test and then followed it up with a thorough visual inspection.
But preceding both the road test and the visual inspection another question had crossed my mind. I should have asked the customer if there was any recent work performed on the vehicle, and if so, did the fault surface after that work was performed? The answer to both of those questions would have led me to the next — What work was performed? (Or, can I see the invoice?)
The customer would have told me that an engine transplant was performed. I realize now, through experience, that some of the most difficult issues to find are man-made ones. A thorough visual inspection would have brought me directly to the culprit in no time at all.
Initial Approach
So, how did this alter the way I approach driveability issues? I begin my approach to any issue as an opportunity to gather valuable information pertaining to the nature of the symptom/concern. As you’ve seen in my previous articles, a customer interrogation is crucial. I learned this from my mentor, Jim Morton. He led by example as he solved an average of 28 driveability symptoms per day. That type of proof cannot be argued with.
Performing basic tests and documenting the results yields a lot of overall generic information about the vehicle and puts a lot to rest early in the process — things like the functionality of the battery and charging system. Being the heart of the entire vehicle, I wouldn’t expect anything to function properly without this system in proper working order. These take a few moments to do and then they can be forgotten about for the duration of the analysis after their functionality is proven to be satisfactory.
Scanning for DTCs vehicle-wide is highly recommended. Seemingly unrelated system faults could in fact be the root cause of the symptoms exhibited — such as an ADAS or 4x4 system fault due to a wheel speed sensor circuit issue. Writing down the DTCs with the order of the approach you have chosen (and why you chose that order) gives you something to reflect on later.
Writing down the component tests performed and where (in the circuit) the data was obtained is another strong lesson I've learned. For instance, testing at a ground-side driven component (like a port fuel injector) at the ECU is basically looking to see if the voltage has not pulled all the way, or close to, ground (Figure 5). That is an expected outcome for a healthy circuit, as an elevated voltage would indicate a poor path to ground. However, if a fault was present closer to the fuel injector it wouldn’t be detected. It’s for this reason I test as close to the load device as possible (Figure 6).
But regarding inputs, I test as close to the ECU as possible. When you take the time to think about it, it’s easy to imagine a sensor functioning correctly but a broken wire or loose connector terminal preventing that healthy signal from being seen by the ECU. How do you think I learned this logic? That’s right, by getting my rear-end handed to me. But because I took the time to journal, I've been able to learn from my mistakes and polish my approach.
Techniques like the ones described above are lessons that are difficult to teach. But believe me when I tell you they are not hard to learn. Slow down, document and revisit the entire job when it’s complete.
Be your own biggest fan but be critical about your approach. Learning firsthand what is working, what is not working, and what can simply be streamlined is invaluable and will serve you well for the rest of your career!
