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What you will learn:
• Customers tend to know more about a fault than they may realize
• Interrogating a customer about the nature of the fault will likely pave a diagnostic path for you
• 'Intermittent' faults are not truly intermittent. They are easy to replicate once the failure conditions are realized.
We have all encountered those troublesome vehicles. Sometimes we are the original shop, which fails to provide a solution, and sometimes we inherit them from others’ failed attempts. We are not perfect and some of these diagnostic challenges can be a bit overwhelming. With that said, I too, have been on the receiving end of these sometimes “nightmare jobs.” But that is not to say I didn’t learn from them.
Years ago, I had realized that the words “intermittent failure” do not truly exist in our world of diagnostics. I now realize that some of you may be bothered by that statement, so please allow me to explain, through example.
Think about the last “intermittent fault” you were challenged with, but successfully diagnosed and repaired. Now, think about when you discovered the root cause of the fault. Is it not true that once discovered, the symptom could be replicated, almost at will? This is because the “fault” isn’t what’s intermittent; it’s the conditions that cause the symptom, that is truly “intermittent.”
Hungry for hotdogs
Years ago, I was approached by an older gentleman that told me a story of his vehicle, illuminating a MIL intermittently. He claimed it was only when he stopped to grab a hotdog, for lunch. He assured me that it was, indeed, the only time this fault occurred. With a carefully hidden smile, I was happy to investigate further, although I wasn’t truly convinced the hotdog had anything to do with this fault. It was very likely a simple matter of perspective.
Before approaching the vehicle, I had begun to interrogate the customer. Many people find that word offensive, but I have a job, not a hobby. “Efficiency” is just as important to me as “accuracy.” The more information I can obtain before approaching the vehicle, the more efficient I will likely be.
My interaction with the customer began with a question about where he gets his hotdog. The place was quite famous, and I know exactly where it's located. It is at the base of a very long and steep upgrade. He stops for the hotdog each time he must travel across the state for his weekly work function, and proceeds (hotdog in-hand) up the hill, towards his destination. This is where my brain starts to do its thing.
I first approached the vehicle with a scan for DTCs. Not surprisingly, one was in history, a P0171 “Bank 1, system lean.” A quick visit to Freezeframe showed the fault presented under that heavy/sustained load the customer described.
I told the customer that I would be taking the vehicle on a road test to gather some data, for analysis. I returned in less than five minutes, with a preliminary diagnosis of a lack of fuel delivery. Further, pinpointed testing took another 15 minutes, and I had a conclusive diagnosis of a restricted fuel filter.
We can’t always be the hero, but when taking the time to extract the data from the customer, before attaching the vehicle, you set the stage for efficient analysis, or gathering of data. Customers typically know a lot more about the situation than they believe. Try it and you’ll likely concur, “intermittent faults” are typically just a matter of perspective.
