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2002-2005 Range Rover MkIII / L322
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I just purchased this 2004 Range Rover Westminster and in the first 20 miles it got a check engine light for codes P1170 and P1173 I read a lot of the posts on rangerovers.net and any place else to get info on the problem. My son has a Mercedes and BMW repair shop and is familiar with this engine so we put it up on the lift and replaced the before and aft O2 sensors after 30 miles the code comes back. We also had a coolant leak at the valley cover so after removing the intake I replaced the PCV valve assy. and all related hoses gaskets and seals. Also replaced Mass Airflow sensor air cleaner and spark plugs after 30 miles the codes come back. Next we smoke tested the intake and crankcase ventilation system found leak at the throttle body adaptor removed and replaced seal. Next we smoke tested the Exhaust system found crack in weld on left cat. and heli arc welded the cat and pressure tested no leaks and the codes come back. By this time we are scratching or heads on this one.
The next step was to visit and old friend that has a auto repair shop to see if he still had a five gas tester to see if the cats are bad only to find out that if the car isn't on a dyno it wont tell up much. his top tech which isn't versed on European cars at all went to a web site Identafix I think and some one had posted that they got those codes after they had a transmission swap and found that the aft o2 sensor leads got switched. So that put me on to something I ordered a factory electrical manual with diagrams and we started checking wire colors to find out according to the book my front sensor leads are switched so we swapped them and now the Snap on scan tool says they are reversed so we switched them back. The book also shows the rear leads are correct so I figure that if the fronts are reversed according to the book the rear sensors need to be reversed also, we swapped them to match the fronts and that corrected the problem. After 100 miles and no codes and all the monitors are cleared I think that I am ready for a smog test. I have not clue as to why my cars wiring doesn't match the wiring diagrams or how the leads got swapped sense the last smog test but this corrected the problem. I have spent weeks trouble shooting this problem and the scan tool will not tell you the rear sensors are reversed but if you are getting left and right before cat o2 sensors aging and both codes going off together this is something to check. I hope that this helps someone in the future.
 

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2010 SC 5.0 Range Rover MkIII / L322
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2,046 Posts
thanks for posting what you found
 

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All I can say is wow. Hope you got the range for a good number. And welcome to the site
 

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Hello everybody, hopefully your knowledge can help me finally get this problem fixed.
I have a 2003 RR HSE 4.4 with 143k miles. CEL comes on after driving it about 30 miles. Codes p1170&p1173. So far I've replaced, intake gaskets, PCV, crank hoses in the back of engine, MAF sensor, 2 front O2 & 2 back one (4 total) reset adaptations with my scanner, inspected the cats for cracks, and checked to the best of my abilities for any vacuum on the engine. I pulled the spark plugs out and cleaned them too. Codes still come back on. Truck leaks oil from both head covers? Could that be it? I will take care of that leakage, but before I start taking it apart I want to get rid of the LEAN codes. I also have the FREEZE DATA but I don't know how to diagnose using that info. I dont know what short trim or long trim mean or Bank 1&2 CL. Any help or direction to follow will be tremendously appreciated.
 

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2002-2005 Range Rover MkIII / L322
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according to the book the rear sensors need to be reversed also, we swapped them to match the fronts and that corrected the problem. After 100 miles and no codes and all the monitors are cleared I think that I am ready for a smog test. I have not clue as to why my cars wiring doesn't match the wiring diagrams or how the leads got swapped sense the last smog test but this corrected the problem.
I am having this same exact problem currently. Can you explain exactly what was switched with the wiring? Did you have to cut the wires or did you switch them where the wires meet the connector? Thanks in advance for your help!
 

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I am having this same exact problem currently. Can you explain exactly what was switched with the wiring? Did you have to cut the wires or did you switch them where the wires meet the connector? Thanks in advance for your help!
Yes I agree how do you switch the wires, I also have the same problem, new cats, no leaks, code come up...?
 

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2002-2005 Range Rover MkIII / L322
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UPDATE for anyone who may be having this problem...got new cats and it solved the problem finally.

I went to a muffler shop and got them for $480....the dealership I got a $360 diagnostic from (Thousand Oaks, CA - DON'T GO THERE they are scam artists) gave me a $7,200 estimate to replace them.
 
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