How did you finally break through that mental block after the customer left? I had a similar wake-up call with my own truck, refusing to use a code reader for a check engine light that turned out to be a failed sensor. Spent hours swapping parts blindly before caving and plugging in a basic scanner. Now I make it a RULE to check the computer first, even for things that seem obvious. That shift in mindset saved me so much frustration and actually made repairs fun again. Stubbornness really is the enemy of efficiency, huh?