Throttle position switch TPS
 

If the ICV does not work properly, also check the TPS on the throttle housing. When idling (not touching the throttle pedal), the orange wire (pin 1) should be earthed via the black wire on pin 2.

Thanks to all for your help & information. Il try another icv & see what happens. Spose this should teach me a lesson with buying cheaper parts as its the only non genuine part that i have replaced thats failed.

Tps shows increasing voltage when back probed and put through movement. But i do have a spare tps in my box should the original fail.

It might not have failed, if you still have the original clean it out with something to break down any oil in it and then give it a go again. The originals rarely fail,they are also a generic Bosch part so are used on other makes and models of car.

Yeah im just about to try the original one just to see if it clears the code however i think this one is toast. Neither of them are seized though and go through full movement.

I disagree. Take a look at the diagram and the explanatory note top centre on Page 26.

7/75 is the bulb failure sense resistor. Its shown simplified. In other diagrams, it is shown as a part of other bulb circuits. Its shown in the electrical distribution box on page 126 (just next to the fuel pump relay position)

The dim/dip voltage is electronically reduced by the electronic regulator component 2/3.

Unless the system had some form of modification or downgrade in later years, I don't know what the long resistor does, but its not dim/dip voltage reduction.

You're right Ash, i was still half asleep when i added that, maybe why i TARFU'd it! ;)

*** EDIT *** i have seen a dim-dip resistor used on other cars including Volvos so maybe they did add it in there and change that regulator for a dim-dip relay. You know what they say "Volvo reserve the right to change specifications etc"

A resistor would not make sense in that use anyway - the voltage drop would change too significantly if a filament went open circuit on one side, or if different wattage bulbs were fitted.

I strongly suspect the long resistor is something else, not related to the lighting circuits

0.9 Ohm resistor
 

It is actually item 7/46, a plain resistor, nothing else to it and it IS the one in the picture.

About the ICV, just ground pin 1 of the TPS and start the engine. Just to be sure...

Thanks Rob. ;) :D


You're right Ash and that has been the primary cause of failure of many dim-dip systems. It's how it's usually done though.

https://s19.postimg.cc/brewx3feb/dimdip1.jpg

https://s19.postimg.cc/o61oxez6r/dimdip2.jpg

That's a much simpler system but still uses a simple wirewound resistor mounted on an aluminium heatsink bolted below the LH headlamp on the car that diagram pertains to. Many others were done in a similar way. ;) :D