Hello all, I just recently purchased a 2003 Discovery II (VIN out of the death range). I have had it about 2 weeks and the check engine light has come on with code P1173 (Upstream Sensor Aged ATV Adoption too lean RH bank).
I searched the forum and found a number of threads talking about PCV hoses but they only seem applicable to pre-2003. Mine has the SAI.
Other option I saw said it could be the HO2S sensor.

I reset the light and it stayed off for about a week and came back on. Anyone have suggestions on best way to approach.

Only other problem I have found with it so far is that the drivers rear door does not lock/unlock - I think the actuator is dead and needs replaced.

 

That code is for the O2 sensor begining to fade out. The system tests them to see that they can still work correctly to filter pollution, and when they get marginal this code is produced. Some codes like this will come back when cleared, but only after several "drive cycles".

The PCV system, if present, looks like one of the attached, a vent hose from each valve cover, the one on passenger side has a spiral oil separator that gets clogged, clean with carb cleaner.

There have been posts about cleaning up the PCV system and this code staying reset. Obviously cheaper than O2 sensors.

BTW you will engjoy the free download of the shop and owbner's manuals, called the RAVE, below. Short for Rovers A'int Very Economical....

 

John,
How many miles on the truck, when did it have it's last major along with new 8 mm silicone plug wires and have the 02's ever been changed?

 

It has just under 104K on it. Only had it for 2 weeks. Looks like all the service was done at the local land rover dealer but not sure what was done - Carfax just shows service - I would guess the O2 sensors are original.
I was going to look at the PCV baffle and see if it is clogged and then move on to the O2 sensors.
I believe the front O2 sensors were reading like .6 and the rear ones were like .4 when I scanned the codes the other day.

Not sure about the plug wires either - they are grey and numbered but I dont know if they were replaced or not? It looks like it would be a PITA to replace them.

 

The wires have to go, they are the original factory crap that was never any good.
Don't worry about the oil separator, you need to change out all 4 02' s that are now a little warn out, make sure to do my entire major service list posted at the top of this section along with rebuilding or replacing the front drive shaft if it has not been done yet or before it fails and takes out the tranny.

 

Mike is a realist, once a single O2 goes, the others will be along in a few miles.