C30 2000 V70R B5244T2 - P0422 Main catalytic converter, bank 1 efficiency below threshold

Hi Guys - have an issue and not too sure where to go next. I live in a small town and so far 3x "mechanics" either do not know or are not willing to touch the car.

I have an error code of P0422, which indicates I should be replacing the oxygen sensors and/or the CAT converter. What concerns me is the engine feels very hot, intake manifold included, to the point where ignition coil wiring was being melted and the blue spark plug/coil pack cover was being cooked.

Should I be looking at the turbo and making sure it is bolted on properly, and exhaust gases are flowing correctly? Or would a faulty CAT potentially foul the exhaust flow and cause excessive engine heat? Many hours of Google searches make me think it could be PCV trap, turbo bypass valve, turbo/exhaust manifold loose, air/fuel lean or rich, or something else entirely. I'm a bit lost to be honest.

Other symptoms:

- Cylinder 3 black (see photo - wiring has since been repaired).
- Fan stays on after short drives in cool weather.
- Performance when car is warm degraded.
- Idle when warm slightly wobbly.
- Air intake temperature high.
- Rich smell first start.

What I have replaced/fixed so far in the last 3 months:

- ETM repair kit.
- Turbo Control Valve and MAF.
- Heater hoses and heater core.
- Main coolant inlet pipe on back of block.
- Fuel pump relay.
- Fuel filter.
- Fuel pressure damper.
- All coolant hoses.
- Thermostat.
- Ignition coils.
- Spark plugs.
- Injectors.

I am hoping someone has experienced a similar issue and can nudge me in the right direction. Thanks in advance.



  • GhettobirdJulian @Ghettobird Melbourne - SE Suburbs
    edited October 2018
    Id be looking at the O2 sensors, then Id be doing a compression test/ Chem test to see if maybe the head gasket is toast.

    Exhaust gas flow wont cook a plug cover like that, Its likely overheated at some stage and you are experiencing the aftermath.

    All x70 cars have crumbling wire harnesses on top of the motor, but most dont melt their covers like that.

    Does it pressurise the expansion tank when its cold? Is it consuming coolant?
    Id say the wiring repair is unrelated, as is the PCV and CBV are totally unrelated to the heat related issues

    Check its not the head gasket, check and see if the water pump is doing its job (If its stuffed the damage is already done), Look for VAC leaks on the intake manifold and Turbo pipework that would cause a crappy idle, and then look into the PCV and wiring

    My money is on the Coolant temp sensor, maybe the head gasket and O2 sensors, then maybe a clogged cat

    Good luck!
  • Thanks for the detailed response Julian, much appreciated!! I will get my hands on a compression tester and give that a shot this weekend... then start picking my way through the list.

    Will post an update here (might take a while) when I have a solution. Looks like FCP/IPD are going to get even more of my retirement fund.

    Thanks once again.
  • GhettobirdJulian @Ghettobird Melbourne - SE Suburbs
    No worries!
    Post up what specific bits you may be after in the future, there are some parts that are actually more reasonable getting locally
  • Plugged cat can cause heat build-up in my experience on a 240 turbo in the US...one way to check is to remove it and have a look at the core. Not sure how hard it is on the V70.
  • Right I have replaced the coolant sensor and in my travels found the drivers side ambient air temp sensor was just dangling... previous owner had cable tied it to a bunch of other wires beneath the headlight. I would really like to install it in the correct spot but I can't see any obvious mounting points. The passenger side is in the fog light grill, no such joy on the drivers side.

    Part number is 9125603 and the closest I found was another forum post but I still can't see where it might live from the photo supplied here: https://www.matthewsvolvosite.com/forums/viewtopic.php?f=1&t=74374

    According to the above link it is the air temp sensor that talks to the ME7 so I would prefer it was in the right spot rather than jerry-rigging it to something else. Any clues or photos would be greatly appreciated! Thanks in advance.
  • Just in case anybody is still lurking this thread. I replaced the coolant sensor which didn't seem to make a huge difference. Water pump, thermostat, coolant sensor, fan all working as they should.

    Another interesting observation, flushed the oil over the weekend and it had a pretty strong smell of fuel. Will flush the oil again sooner rather than later to see what condition it is in... so I guess I'm looking at compression / valves / rings. No shiny metal flakes/sparkles in the oil.

    Booked in to a fuel injection specialist next month to see what they can find. Wish me luck.
  • How’s the fuel pressure?
  • @carnut222 great question!! I will order a new fuel pressure regulator (have a new filter ready to install as well)... I know fuel pressure at the rail is there after replacing the injectors and copping a good spray, but whether or not it is too high/low/inconsistent I am not sure. Will give you an update once installed, thanks for the suggestion.
  • Ex850RSnoopy @Ex850R Somewhere Over the Rainbow. Melbourne.
    Fpr is the usual suspect.
    Replace before spending on a shop visit.
  • Hi team - still waiting on new fuel pressure reg to arrive, will update once installed.

    Interesting note, the car ran really well for 3 weeks (longer than it has ever gone without throwing an error code) with a lot of driving after the oil flush. No error codes, good fuel economy. The oil smells again now of fuel and I'm getting the same original error code, with rich smell on cold/warm starts.

    I think I read somewhere that a faulty regulator can leak fuel into the vacuum lines and cause the issue I am experiencing, fingers crossed this is the solution.
  • gavinhGav @gavinh Parmelia, Perth
    Interesting read, hope you sort it out soon. This forum is great, ou thin you have covered all the bases and some one chimes in with something that has been over looked.
  • Another update a few months down the track - basically the fuel reg I ordered was never shipped, and I have only just got to finding a replacement, hopefully it arrives in the next week or so. Also started getting a new error code: ECM-644A, Reset valve, camshaft.


    Performance has been absolutely woeful in the last couple of weeks, it was struggling to get to 100 but once there seemed to cruise OK. Also made a horrible droning sound, which I would normally attribute to an exhaust leak, but because the error code is specific to the exhaust side solenoid I assume it is something there not working correctly.

    I noticed there was a bit of oil in the solenoid connection, assuming it has died I have ordered a replacement kit with all the bits. I also checked resistance and it was very low, I think I read on another forum it should have been around 3.7ohms and it was much lower, so decided a replacement was the best bet.

    Wish me luck, hopefully this is the light at the end of a very expensive and frustrating tunnel. I'm kidding, the brake lights are staying on until I give the brake pedal a whack with my foot, and number plate lights work intermittently, so thats going to be heaps more fun.
  • VVT solenoid unit replaced, faulty part looks different and out of a used XC70. Probably doesn't make a difference but took the car for a test drive and it is noticeably much better. Here is the old unit for anyone interested:



    Now to install the fuel pressure regulator and see what happens! I still have not received a shipping confirmation, so I'm thinking it might be worthwhile installing an aftermarket regulator, perhaps something like this: https://www.carmodsaustralia.com.au/universal-adjustable-fuel-pressure-regulator.html
  • Much anticipated update time. Fuel pressure regulator was replaced, but we did test pressure before installation and it held around 55psi consistently. Even a few hours after shutting down the car, the pressure held. Same error code.

    I have just installed a new fuel filter and oil flush, next thing I will do is book into the local exhaust workshop and make sure intake/exhaust gaskets are fine, and replace the sensors + cat. Fingers crossed, otherwise I am running out of things to replace!!
  • edited June 2019
    My suggestion would be to fit an 02 spacer to the rear oxygen sensor. Much cheaper than replacing the cat
  • For anyone interested, which will be precisely 0 people, I ended up replacing both O2 sensors and the CAT. V70R drove for around 200km before throwing a new code:

    Time to start chasing air leaks etc, think I replaced the MAF about 2 years ago. Thankfully I believe I am seeing the light at the end of a very long tunnel.

  • Ex850RSnoopy @Ex850R Somewhere Over the Rainbow. Melbourne.

    i think you need a Volvo VIDA and DICE code reader , all other ones don't read Volvo codes properly , you will be chasing irrelevant codes forever......

  • Vida/Dice is the way to go. At least then you'll know if the fuel trim is at the upper or lower limit... big difference there.

  • @vvvolvooo

    Where in Australia are you? I get out to middle of nowhere on a regular basis so wondering if I can't make an easy side trip to see you and plug a dice/Vida into the car and give you some answers to what is actually wrong

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