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Previous Thread Next Thread Print Thread Rate Thread 1999 Montero Sport PO421 code #1027198 04/25/11 01:35 AM Joined: Jun 2010 Posts: 38 So.Cal rollguy OP Getting the Wheeling Fever I have a PO421 code (warm up catalyst efficiency below threshold bank 1). Does anyone know what part/s would need to be replaced to fix it? I think it could be the catalytic converter, but it may be something simpler (O2 sensor?). Any help would be appreciated. Thanks, Rich All Diesel Fleet: 1985 Mitsubishi 2.3 Turbodiesel Pick-up, 1983 GMC Van- 6.2 Diesel. Benzs: 1995 E300 diesel, 1980 300SD, 1982 300CD, 1983 300D, 1985 190D. 1980 AMC Eagle Limited Wagon powered by: 3.6 Litre I6 VM Turbo Diesel Engine (one of fewer than 10 made, only 2 known to still exist) Re: 1999 Montero Sport PO421 code [Re: rollguy] #1027199 04/25/11 05:20 PM Joined: Jan 2000 Posts: 16,227 Bay Area, CA off-roader Web Wheeler Quote I have a PO421 code (warm up catalyst efficiency below threshold bank 1). Does anyone know what part/s would need to be replaced to fix it? I think it could be the catalytic converter, but it may be something simpler (O2 sensor?). Any help would be appreciated. Thanks, Rich What's the mileage and are you smoking from a valve guide seal issue? Perhaps the cat's plugged if you've been burning oil but honestly can't be sure. Hopefully someone else can chime in with some better ideas. Re: 1999 Montero Sport PO421 code [Re: off-roader] #1027200 05/11/11 09:35 PM Joined: Jun 2010 Posts: 38 So.Cal rollguy OP Getting the Wheeling Fever No smoke that I know of. I wanted to find out if something simple may be wrong before starting to replace expensive parts. Also, does anyone know which side bank one is on? L or R? All Diesel Fleet: 1985 Mitsubishi 2.3 Turbodiesel Pick-up, 1983 GMC Van- 6.2 Diesel. Benzs: 1995 E300 diesel, 1980 300SD, 1982 300CD, 1983 300D, 1985 190D. 1980 AMC Eagle Limited Wagon powered by: 3.6 Litre I6 VM Turbo Diesel Engine (one of fewer than 10 made, only 2 known to still exist) Moderated by  4x4Wire, Macka, Mudraider, off-roader, PHIL_, rxinhed  Hop To Mitsubishi Forums ------  Mitsubishi 4x4 and SUV Tech  Mitsubishi Diesels  Mitsubishi ArchiveToyota Forums ------  Early Toyota Trucks  Toyota 4Runner, FJ Cruiser &...  T100 & Tundra Forum  Tacoma Forum  Toyota Tech ArchiveJeep Forums ------  Jeep Talk  Jeep TechIsuzu Forums ------  Isuzu 4x4 & SUV Talk  Isuzu 4x4 & SUV Tech  Isuzu DieselsKia Forums ------  Kia Talk  Kia Sportage & Sorento TechOff Topic Chat ------  4x4 Gallery  Off-Topic Chat  Recreational Access & Land ...  Politics4xForums ------  Outdoor Gear  General 4x4 Discussion  Tools and Fabrication  General Communications  Amateur Radio  GPS and MapsParts Bin ------  Private Party - Garage Sale  Private Party - Items wanted  Vendors, Hot Deals, Group Buys4x4Wire Back Yard ------  Suzuki Forum  AZ Crawler Crew  Cal-Nev Crew  General Ford 4x4 & SUV Forum  General Dodge 4x4 & SUV Forum  General Chevy 4x4 & SUV ForumFeedback & Testing ------  Problems, Questions, Suggestions4x4Wire Staff ------  Forum Moderators  Problem Threads Print Thread Switch to Threaded Mode 5 Excellent 4 Good 3 Average 2 Bad 1 Terrible View Profile Private Message Follow User Forum Posts View Profile Private Message Follow User Forum Posts View Profile Private Message Follow User Forum Posts

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