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  1. #1
    Join Date
    Aug 2016
    Location
    Austin, TX
    Posts
    6

    Default P0420 code thrown after replacing Catalytic converter with aftermarket Cat

    All, I recently replaced my Catalytic converter after the check engine light came on. After looking up the prices, I bought an aftermarket CAT from carparts.com and took it to my mechanic. With labor and the cat it came to around $600 which is half of what i was quoted elsewhere. Long story short, i also replaced the plugs and a few bad coils along with the Cat. After driving 20 miles or so, the check engine light came on and it's still throwing code P0420. The mechanic checked the 02 sensors which are fine and surmised that the computer is set for California emissions standard while the CAT we installed does not. Ripping and replacing with a California emissions spec'd CAT is not an option. So, i'm considering a hack of the 02 sensors. I've seen a mechanical hack using a spacer screwed on the end of the 02 sensor and an electrical one adding a capacitor and resistor to the electrical leads that plug into the sensor. The mechanical hack is what i'm leaning towards but I've never done this before. Has anyone tried this with success and if so, can you give me some guidance on what exact parts to buy to accomplish this? Thanks in advance!!

  2. #2
    Join Date
    Apr 2016
    Location
    California city ca.
    Posts
    24

    Default

    The car should be 50 state compliant on the CATS & all.

  3. #3
    Join Date
    Mar 2005
    Location
    Pacific Northwest
    Posts
    1,921

    Default

    Spacers worked on 2 cars (01 Prius, 00 V70XC) I've tried it on with P0420 code so thats a good bet for you. Basically it pulls the downsteam O2 sensor out of the exhaust flow and makes the ECU think CAT is functioning at good efficiency.

    I got perfect fit O2 extender for the 00 V70XC from ebay for like $6. Spec was M18 (thread) x 1.5 (length in inches I think). Just search "o2 extender M18" on ebay. Get the straight one and not the one that makes a 90 degree bend. Avoid following some online suggestions to buy spark plug extenders from local auto parts store which requires drilling out to fit the O2.

    I've also read people having success washing the old cat. I guess it cleans and exposes more of the catalytic surface. I've not tried this myself
    Past Volvos : 01 V70 T5, 01/02 V70XC, 02 V70 NA, 00 V70XC
    Current EV/Hybrid : 13 Tesla S85, 11 Gen3 Prius
    Friends cars under my care 17 Audi A4 Quattro DSG (B9) 05 Audi A4 Manual 6sp Quattro (B7) 04 e320 V6 Auto, 05 Accord 2.4, 08 Element 2.4, 08 Camry Hybrid
    Past Others : 01/03 VW MK4 Turbo/NA/01M. Gen1 Prius, Gen1 CRV, Gen2 Rav4, 02 Town&Country, 06 Corolla, 12 Audi A4 Quattro (B8), 07 Civic 1.6
    http://www.freewebs.com/howardsvolvos/

  4. #4
    Join Date
    Aug 2016
    Location
    Austin, TX
    Posts
    6

    Default

    Makes sense but i can't think of a reason a brand new cat would throw the code unless the software is the issue. I guess i'll know for sure when i do my yearly emissions test. The part i bought is legal for 48 states, all but CA and NY. http://www.carparts.com/details/Evan...EPV960317.html. Thanks for the feedback!

  5. #5
    Join Date
    Aug 2016
    Location
    Austin, TX
    Posts
    6

    Default

    Thank you for the response Howard. Tha'ts exactly what I'm looking for. I haven't crawled under the car ever. Does the sensor screw into the CAT in a place thats accessible without removing much if anything? The installation required 2.5 hours of labor at my mechanic so I'm hoping the sensor part is easily accessible.

  6. #6
    Join Date
    Aug 2016
    Location
    Austin, TX
    Posts
    6

    Default

    Aerobatics fan. So you're saying the 02 tolerances should be low enough for all 50 states. It makes sense but the CAT itself is only compliant for 48 states excluding NY and CA; hence the theory that the software is the issue. I guess I'll know once I do my emissions test next year if its the sensor, software, or the CAT. Thanks for the feedback!

  7. #7
    Join Date
    Mar 2005
    Location
    Pacific Northwest
    Posts
    1,921

    Default

    Quote Originally Posted by gpaustin View Post
    Thank you for the response Howard. Tha'ts exactly what I'm looking for. I haven't crawled under the car ever. Does the sensor screw into the CAT in a place thats accessible without removing much if anything? The installation required 2.5 hours of labor at my mechanic so I'm hoping the sensor part is easily accessible.
    Was easy to get to on the 00 V70XC so hopefully same for your car.

    Can't remember if I got it out with a big crescent or needed a O2 socket/crows foot (I don't have O2 socket but crows foot does the same) I vaguely recall removing the connector end was a little tricky as well. Here is the directions on the older gen car. Probably pretty similar.

    http://www.pelicanparts.com/techarti...eplacement.htm
    Past Volvos : 01 V70 T5, 01/02 V70XC, 02 V70 NA, 00 V70XC
    Current EV/Hybrid : 13 Tesla S85, 11 Gen3 Prius
    Friends cars under my care 17 Audi A4 Quattro DSG (B9) 05 Audi A4 Manual 6sp Quattro (B7) 04 e320 V6 Auto, 05 Accord 2.4, 08 Element 2.4, 08 Camry Hybrid
    Past Others : 01/03 VW MK4 Turbo/NA/01M. Gen1 Prius, Gen1 CRV, Gen2 Rav4, 02 Town&Country, 06 Corolla, 12 Audi A4 Quattro (B8), 07 Civic 1.6
    http://www.freewebs.com/howardsvolvos/

  8. #8
    Join Date
    Aug 2016
    Location
    Austin, TX
    Posts
    6

    Default

    Thank you! I'll let you know how it turns out!

  9. #9
    Join Date
    Dec 2004
    Location
    Connecticut, US
    Posts
    274

    Default

    In my 05 XC70, there is no room above the cat for a straight spacer. So I have to buy one with a 90 degree angle.

    DYZ
    2005 Volvo XC70, Ash Gold, 198K miles

  10. #10
    Join Date
    Apr 2016
    Location
    California city ca.
    Posts
    24

    Default

    I got my 05 from Ga , processed it here in CA & they never said a thing at the DMV tag office, I did get it smogged & it passed with ease. Befor it was delivered to me I did check to order a replacement exhaust system & no mention of 48-49 state or CA only. My T-bird is a 1995 & it is 50 state.

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