Diagnostic Dilemmas: Code Talking
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Diagnostic Dilemmas: Code Talking

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This being the 60th anniversary of the end World War II, I’ve seen several television programs and movies about how Navajo Indians used their native language to relay a simple military code in the war’s Pacific theater. In order to break any code, it’s important to understand the language in which it’s transmitted. The Navajo Code Talkers, as they came to be known, could broadcast at will because the Japanese military didn’t have anybody who could understand the complex Navajo language. For this reason, the United States gained a decisive military advantage that drove us to eventual victory in the Pacific theater.

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Most recently, I’ve diagnosed a number of vehicles that reminded me of the Navajo Code Talkers. In order to understand the diagnostic trouble codes produced by these vehicles, I had to understand the context in which they were broadcast. The context, of course, is not the codes themselves, but the symptoms that they represent.

The Tell-Tale Toyota
To better illustrate, let’s begin with a set of misfire codes stored in the diagnostic memory of a 1997 Toyota 4Runner that was referred by a neighboring shop for an MIL-on condition with an intermittent stall, and cranking, no-start complaint. Since the owner was a real estate agent operating in mountainous areas, he was extremely fearful of embarrassing himself by being stranded in the mountains with a carload of sales prospects.

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I could retrieve a series of engine misfire codes which were: P0300, 301, 302, 303, 304 and 306. Going back to basics, the PCM indicates a misfire by detecting slight changes in crankshaft speed at the crankshaft position sensor. Clearly, the PCM thought it had detected a misfire on all cylinders except number five. The freeze-frame data indicated that the P0300 condition had occurred at 1,500 rpm, 14 mph, closed loop, 190

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