Thanks to our Partners, Pico Technology, Autel, and Independent Wrench Jobs
In this episode of Diagnosing the Aftermarket A to Z, Matt Fanslow tells the story of a modified 1994 Corvette that came in with a hesitation, backfire, and cut-out concern under light-load highway driving. The vehicle had already been looked at elsewhere, and the customer believed the problem was inside the PCM. What sounded at first like a computer problem eventually turned into a lesson in secondary ignition leakage, diagnostic assumptions, customer expectations, and the danger of two people using the same words to mean very different things.
The episode starts with the question, “Can you test my computer?” Matt interpreted that as a request to diagnose why the vehicle was not running correctly. The customer meant something much more literal: open the PCM, test it on a bench, and determine what had failed inside the module. That misunderstanding created real tension once Matt found evidence pointing away from the computer and toward the ignition system.
Technically, the case had plenty of reasons to look complicated. The Corvette was a 1994 OBD-I vehicle with an OBD-II-style connector, an aftermarket tune, a DTC 42 related to electronic spark timing, and an OptiSpark distributor system. Matt considered scan-tool access, PCM powers and grounds, tune corruption, OptiSpark signals, and even inspected the PCM itself. But the actual fix was far more ordinary: spark plugs and plug wires. A light mist of water exposed secondary ignition leakage, with arcing visible around the plug wires and spark plug area.
The larger point of the story is not just that simple failures can hide behind complicated symptoms. It is that assumptions can create their own problems. The customer had one expectation. The shop had another. Nobody was necessarily acting in bad faith, but the mismatch still led to frustration, anger, and a near breakdown in trust. Matt reflects on how one better question at the beginning, “What do you mean when you say test the computer?” could have changed the entire interaction.
Topics Discussed
Key Takeaways
Thanks to our Partner, Pico Technology
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From drivability diagnostics and TPMS service to ADAS and advanced safety systems, Autel helps technicians follow OEM procedures and repair with confidence. Learn more at Autel.com
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Contact Information
The Automotive Repair Podcast Network: https://automotiverepairpodcastnetwork.com/
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