The pre-turbo sensor reading difference between 2 shops in Boise

Got my Freightliner back from a shop in Boise that swore the EGTs were fine, then drove 4 hours to another guy in Twin Falls who actually pulled the pre-turbo sensor and showed me a 300 degree gap on the same stretch of interstate. The first shop just cleared the code and called it good, but the real story was the manifold gasket leaking and throwing off all the readings. I've seen this before on older Detroit motors, but it took me 12 years to find a tech who bothered to check the delta before saying it was fine. Anybody else had a shop skip the obvious comparison test and cost you a whole day of downtime?

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robins831mo ago

That delta check is the whole ballgame right there. Seeing the split between pre and post turbo tells you exactly where the restriction is, or if the sensor itself is lying to you. Most guys just read one number and chase their tail for hours. The gasket leak throwing off the readings is classic too, because the exhaust pulse messes with the sensor sampling. Good on that Twin Falls tech for actually pulling the sensor and not just trusting the code. Once you see that gap once, you never trust a single reading again. That's the difference between a parts swapper and a real diagnostician. Downtime is money, so finding that guy is worth more than the fuel bill to get there.

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