Any input on how to tackle the diagnosis of the power steering not working
Thanks

First check your fluid level. It's ATF+4 used in our power steering system and there is no recommended fill level, just until it's full on the sight glass in the engine compartment.

It COULD be a PCM/battery issue, check your battery voltage. Low batteries in these monsters cause undescribable headaches.

Power Steering pump could be shot, but this would be the first one I've personally heard of.

Power steering pressure switch could be shot (I would look here after fluid level, remember do the cheaper stuff first.)

The power steering pump pulley is part of the timing belt system, so it's gonna be a real pain in the pooper if it's the actual pump.

I think you access it through the oil pan as well. Bleh.

Start your search on page 4379 of the Service Manual.

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Silver 2006 KJ 2.8L CRD Limited:
GDE ECO Tune / Fumoto Valve / E-Tecno GX3123 7v Glow Plugs / 2nd Gen Fuel Head / Mishimoto RED Hoses / Rockers/Lifters @ 114k / Hayden FC + 11 Blade Nylon / Sears P1 Battery / Transgo 45RFE-HD2 Reprogramming Kit / Timken Front Bearings