2.5 20V GLT automatic 1993 VDO not working
 

My 850 2.5 20v GLT Auto has a problem with the digital trip computer

The fuel parts return 99.9 mpg both average and standard.
The ambient temp gauge rises 1 degree C every few mins till 43 degrees C then stops and starts lowering.

Also the mph is a bit slow less I reset it.

I have ran the diagnostics in pin 7 and go 1.2.2 saying the temp is too long

any ideas

Trip computer not working
 

According to the wire diagram it may be the coolant temperature sender at fault. Its the digital trip computer at the base of the instrument cluster I believe it was an optional extra.

Any got any idea if I'm on the right track