It does not read the cat heating up.. the delay shift is there for the purpose of HEATING the cat as rapidly as possible if the collant temp is low.

The code is monitored by the rpm and ECT sensor.

If one were to warm the car first or hold the car in lower gear for first start, the code will never come on regarldess of the vac element being bad b/c the delay SOV signal will not be called for by the ECU....
..which is why guys 'BB" the SOV feed vac line.....

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A Dalton

hi i am in desperate need of help my cars cel came on yet again! theres only one code this time now 'p1700' (upshift delay switchover valve) everyone i ask has no idea, what it is, i dont even have a general idea what it looks like. i cant even seem to find it. "problems it has" not all the time but idle will shoot little over 1000 then very low and the lights come on as if it dies but dont at stop lights it dont like to move as if its not getting fuel if i give full throttle clears up and acts normal. Does anyone have a picture of what this thing looks like and where it is located at? please any help will be greatly appreciate! items ive recently replaced maf sensor fuel filter & regulator, alternator. wiring seems to be fine

Where is it located? & what does it look like? On my 1995 c280 where do the lines go too. P1700 upshift delay switchover valve.