I've been ignoring it for quite a while (few mos.) so I pull the intake manifold and take out the coolant temp sensor under the 3rd intake runner and do a resistance test in cold to hot water comparing it to my spare. Both checked out exactly according to the info in the FAQs. I put things together and same thing, dosen't matter if it's hot or cold the "service" light comes on for the first 5-10 mins of driving. The only effect I have noticed is that between cold and hot operation the engine is a little unresponsive in the off idle to mid range (I never like to stomp it till well warmed up). The tail pipe is showing a lot more soot than I think is healthy (rich).
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88 765 w/2stage boost (TO.)