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P0420 - Catalyst System Efficiency Below Threshold Bank 1

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  • P0420 - Catalyst System Efficiency Below Threshold Bank 1

    Hi guys!

    So, my check engine, VSC TRC, VSC OFF and 'skidding' lights came on. While I was just driving along on an ordinary road under ordinary conditions. I got it scanned and it returned only one fault code - "P0420 - Catalyst System Efficiency Below Threshold Bank 1." It was reset, and it came on again after maybe 45 min of driving.

    I've got the 2005 Grande, V6. I only bought it last week so I don't know much about the history, but it has 90,000km on the odometer.

    So I've read there are a bunch of possible candidates - the actual cat converter, one of the 02 sensors, MAF sensor, injectors, spark plugs, an air leak in the intake or exhaust, a coolant leak into the engine...

    Does anyone have any suggestions on where I should start diagnosing / cleaning / fixing?

    THANK YOU in advance!

  • #2
    Replace the postcat o2 sensor first. That was the fix for me (I also had air leaks in the exhaust, changed the spark plugs and injectors which didn't fix it but were due anyway). I used repco sensors.
    2007 GXL V6 - ARB Bullbar with LED lights, snorkel, extractors, 2 1/4" dual exhaust, K&N filter, dimpled/slotted rotors, headrest dvd players, Ebay Satnav/reverse camera, GME 3100TX, Tigerz11 Side awning on custom brackets with Maxtrax mounts, 300W Invertor, ARB Underbody protection, Lightbar and STZ 265/70 tyres.
    Wish list in order I'll get them: Sliders, 2" lift, E-locker, Winch bar with winch.

    Comment


    • #3
      Should I replace both (2x)? If that doesn't fix it, the next 2?

      I found details about checking the air fuel ratio sensors and heated oxygen sensors using a multimeter - checking the resistance across various terminals on the connector. Do you think that's relevant to me?

      Comment


      • #4
        Originally posted by hippo View Post
        Should I replace both (2x)? If that doesn't fix it, the next 2?

        I found details about checking the air fuel ratio sensors and heated oxygen sensors using a multimeter - checking the resistance across various terminals on the connector. Do you think that's relevant to me?
        I would replace both post cat sensors. When I had my issue I swapped the sensors over (left to right, right to left). I still threw the same side error but in the end both were knackered. No point replacing precat, it throws a different code (I've had both). Blocked cats often cause the pre cat sensors to error.
        I read that stuff too, never bothered.
        2007 GXL V6 - ARB Bullbar with LED lights, snorkel, extractors, 2 1/4" dual exhaust, K&N filter, dimpled/slotted rotors, headrest dvd players, Ebay Satnav/reverse camera, GME 3100TX, Tigerz11 Side awning on custom brackets with Maxtrax mounts, 300W Invertor, ARB Underbody protection, Lightbar and STZ 265/70 tyres.
        Wish list in order I'll get them: Sliders, 2" lift, E-locker, Winch bar with winch.

        Comment


        • #5
          Thanks BiLLz0r!

          I'll get some new O2 sensors with the Repco sale on Thursday.

          BTW, if it is indeed a problem with the O2 sensors or cat or something to do with the exhaust, why do my "VSC TRC", "VSC OFF" and skidding lights come on? No other faults showed up on the scan, so I assumed the VSC systems were still working fine and they just light up with the check engine light. However I took the prado out 4wd'ing for the first time yesterday and I was very disappointed that there was no sign of any traction control working! Also DAC didn't seem to do anything.

          Comment


          • #6
            Hey hippo if you are “scanning” with a cheap fleabay BT OBD2 dongle it will bring up some of these faults just after you start driving, happened to me even though they said it was ok for 120 prado, hope that is it. (I ended up with a cheap wifi OBD2 dongle from fleabay).

            Comment


            • #7
              Originally posted by hippo View Post
              Thanks BiLLz0r!

              I'll get some new O2 sensors with the Repco sale on Thursday.

              BTW, if it is indeed a problem with the O2 sensors or cat or something to do with the exhaust, why do my "VSC TRC", "VSC OFF" and skidding lights come on? No other faults showed up on the scan, so I assumed the VSC systems were still working fine and they just light up with the check engine light. However I took the prado out 4wd'ing for the first time yesterday and I was very disappointed that there was no sign of any traction control working! Also DAC didn't seem to do anything.
              No idea, mine only had the engine code light and the scanner (Bosch unit) only showed 1 code.
              2007 GXL V6 - ARB Bullbar with LED lights, snorkel, extractors, 2 1/4" dual exhaust, K&N filter, dimpled/slotted rotors, headrest dvd players, Ebay Satnav/reverse camera, GME 3100TX, Tigerz11 Side awning on custom brackets with Maxtrax mounts, 300W Invertor, ARB Underbody protection, Lightbar and STZ 265/70 tyres.
              Wish list in order I'll get them: Sliders, 2" lift, E-locker, Winch bar with winch.

              Comment


              • #8
                The cheapest one to inspect and clean would be the MAF sensor IMO. Just take the engine cover off, then two screws and an electrical connector and the MAF sensor comes out. A couple of shots of MAF cleaner then install.
                [B]Tasmania 2015 GTG Committee Member[/B] 2005 Prado Pilbara, Sovereign Bar, Driver & passenger weathershields, UHF TX3220, Spare wheel spaces, Lifestyle rack, Genuine front & midrow seatcovers, Genuine front & midrow rubber floor mats, ARB 47 litre fridge/freezer, Hilux washer jets, BF Goodridge A/T, Radiator protection plate, Dual battery tray and isolator, ARB 2.5m awning, Rhino heavy duty areo bars, MSA rear wheel bin, MAXTRAX

                Comment


                • #9
                  Originally posted by Hobes View Post
                  Hey hippo if you are “scanning” with a cheap fleabay BT OBD2 dongle it will bring up some of these faults just after you start driving, happened to me even though they said it was ok for 120 prado, hope that is it. (I ended up with a cheap wifi OBD2 dongle from fleabay).
                  Thanks Hobes and VKPrado - No, this was scanned on a mechanic's scanning tool. I have just bought a cheap ebay $15 Bluetooth dongle so I'll see how that goes.

                  UPDATE - all the warning lights have gone off since my 4WD'ing trip on Sunday... so now I'm confused. Should I still care about it? Or should I wait until they come back on, then clean the MAF and maybe replace the O2 sensors?

                  Oh, and I still don't know why my TC and DAC didn't work on Sunday

                  Comment

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