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The OBDII Test – not the Messiah

OBDII Test – First tier diagnostics

Intriguing to read about all the hype regarding onoard diagnostic testers and wondered how it went this way. One thing is for sure, the OBDII tester in the hands of an incompetent mechanic can do more harm than good.  It cost me $4 000.00 after a nugget of ingenuity, the chairman of The Global Brain’s Trust misdiagnosed a stretched cam chain through some code or other  pulled out of a hat. That cost $1 200.00 – then came the 6 pints of oil used over 30 miles and a damaged catalytic converter. Engine rebuild, a further $2 800.00. What the hell happened up to this point I’ll never know but forgive I’m not – they were the official agents. So lesson learnt.

OBDII Test - the Auto Boss V.30
Auto Boss V.30 – wiki commons credit Florian Schäffer –

OBDII Test vs the Litmus Test

First of all the engine diagnostics tool better known as the OBDII scanner or CANOBDII, is not the only be all and end all of tools to have in your workshop. Sure, it makes life easier but it’s not the Messiah. Think of it as being a simple litmus test i.e. it can give you a general idea as to whether it’s OK. A better analogy would be the oscilloscope used in fault-finding or navigating by dead reckoning. If you don’t know what the wave shape is supposed to look like or your position is estimated you won’t know if it’s correct or not. Seasoned technicians usually have an idea as to what it should like, for instance the output of a Schmitt trigger, but if there is a glitch, is this normal or not? Yes, I have worked on a radar system which had a very strange looking pulse shape in the display circuit – without the manual I may thought it was abnormal. It wasn’t. (DR has been used for centuries, it doesn’t always have to be scientific though).



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