Transmission Fault code P0785 Shift Timing Solinoid Valve open or low input.

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Hi
Our 2002 Vectra C (engine Z22SE) had developed this fault with the transmission. The Fault that GM Holden have advised the problem is from code P0785 Shift Timing Solinoid Valve open or low input.

They took a sample of the trans oil and reported that it is very black indicating an internal fault.

The car goes into emergancy management mode, and i do notice that it appears to "Grab" while putting the car into reverse.

GM advice is to remove and rebuild the transmission or replace with a 2nd hand transmission. Both these costs are quite expensive from $4000.00 to $6500.00.

Could there be something more simpler that could be generating this fault? or is what they have advised is this correct?

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I have had the same with the car spanner symbol and with the car going into limp mode etc

The error code was P0785 Shift Timing Solinoid valve.

The oil in the transmission is black indicating an internal fault.

Two options have been given to me by an Auto transmission mechanic

one to replace the Solinoid and new oil and see if that fixes the problem.

Or expensive option to rebuild the transmission.

If the solinoid is at fault would this cause the oil to go black? or should i be looking at the transmission rebuild?

Any idea help would be great.

Thanks