Hello. First of all, thank you to this community for already getting me out of a few jams in the six months I've had my 2008 lr3.

I have had an intermittent check engine light for about a month now, and just today I received the 4dcan Lr3 diagnostic software with wifi elm327 device from RSW solutions to attempt to diagnose the problem on my own (I am in no way affiliated with this company, but wow...it is a must for any diy rover owners. I already feel like I've gotten my money's worth in the first day of use.)

The software pulled a fault indicating low catalyst efficiency in the bank 1 catalytic converter. I have read elsewhere that this fault can only indicate a failing cat, however, I am also able to look at the live data coming from the 02 sensors to see if they are contributing or causing the problem. The Bank 1 downstream sensor is not transmitting any data.

I am assuming the most cost-conscious way to approach this would be to replace the bank 1 sensor and see if the computer decides the cat is ok after all. What do you think?

Does anyone have any advice as to whether my problem lies in the sensor or the cat? Is it wiser to replace both downstream sensors at the same time?

Thank you all for the advice!

 

Hm, no thoughts?

I have mostly decided to just replace all four oxygen sensors. Although the car's computer is not recognizing any o2 sensor codes, and only shows a fault in the bank 1 cat, the live data indicates that perhaps only one of the oxygen sensors is working correctly (Does anyone know what to expect from the live data from these sensors? I have one sensor, bank 1 upstream, that fluctuates in values between -15 to +15, mostly staying around 0. When car is idling it is mostly between -2 and 2. The other three sensors do not provide any data). At any rate, the '08 lr3 has 93,000 miles, and I'd guess the sensors haven't been replaced at this point, so I'm going all the way on this one.

More questions, which I hope some people can help me with.

I've done some extensive research on 02 sensors, but cannot seem to find a great price on sensors that I am sure are OEM. I don't want to replace with a subpar product, but don't want to cough up $460 or more at AB or the dealership. What brand are the OEM sensors? Are Denso or Bosch replacements acceptable?

I read in a post on another forum that the OEM sensors are Denso, but can't trust the one source.

Once I get some advice on suitable replacement sensors, I will install them and report back to see if it solved my cat fault. It seems to me this post may be helpful to other owners since elsewhere o2 sensor failing is accompanied by codes, but it seems like mine may be failing without any faults. Should I be concerned that this is a problem not with the sensors but with the computer in some way?

 

I would refer you back to the seafoam post and go through that before I replaced sensors. Throttle Body and Induction cleaning, or go have the BG service done. Then re-evaluate after treating the fuel and running it a week.

When I have had similar symptoms, that was the solution.

 

An O2 sensor will not cause a 420/30 fault.

These codes(on this model) are almost always due to oil contamination in the cat, caused by burning oil from a faulty PCV valve. If it is caught early enough, a chemical cleaning will do the trick, but if the oil has been in there long enough to soot up, it's going to be new cats(you'll see a 430 code soon)

For the chemical cleaning, I use BG211, it is far more aggressive than a standard induction cleaning chemical, and designed to clean EGR valves and ports, but will do the trick better than anything else I've found for contaminated cats.

 

Dave , how do you clean contaminated cats ?
Is leaking seal on VVT solenoid would contribute to a sooted cat in the near future ?
Thanks,.

 

I have heard of chemical baths that soak the substrate and help clean it out, but I haven't ever used this method, and considering the amount of labor to R&R the cats, probably isn't very cost effective.

What I use, the BG211, is performed just like an induction service, however this chemical doesn't burn off as easily as the standard BG206. It is a highly volatile chemical, and should be used only after proper training with it, but as I stated above, it is designed to clean carbon build up and deposits from the exhaust system.

To the seal, no. That's just a minor external leak, and aside from a bit of a mess, won't cause any further issues. What needs to be checked is the PCV valve, and make sure that there isn't liquid oil going through it into the intake. I have seen these engine with 5-6k miles on an oil change burn enough to the point that the oil pressure light comes on(down to about 1.5-2 qts left in the crankcase)

 

Thanks for reassurance regarding seal, as i still did not changed a valve cover due to lack of garage and constant cold outside.
As for a PCV valve , I am on the third one , usually changing them every 50 000 miles , last time I checked, there was no visible oil build up or leak thru there . Thanks again. Cheers

 

Thank you for the advice. I've recently cleaned the throttle body, fuel rails/injector, MAF Sensor, and ran sea foam through the tank so I will look into replacing the cat in the near future. Normally I am one for going a cheaper route, but the cleaning sounds like a job I do not want to do, and swapping out the cat is a relatively easy job.

I am still planning on changing the 02 sensors...I gotta imagine that if its possible the cat is failing due to residue buildup, the 02 sensors are likely struggling as well. I'm gonna have to make sure the fuel is ethanol-free whenever possible in the future. (Still no understanding why my 4dcan diagnostic sessions haven't been able to pick up data from 3/4 of the sensors. RSW has been helping me work through what may be going wrong).

Anyone have advice on whether the Denso OE fit sensors function sufficiently in the lr3? I believe they list part number as 234-9075 but that might just be specific to upstream. I have read a bunch of posts, and performed searches, but cannot develop a consensus on whether you absolutely have to use the AB/stealership ones, which are quite expensive.

 

Did you end up figuring it out? I just bought the Denso sensors, but worried they may not fit on my 2008.

Denso 234-4264 and 234-9075

 

Denso sensors are the way to go. They will function as good as OE (they are the same as OE without the Land Rover packaging). It is the same sensors we use at the shop.

The part numbers you listed are correct:

234-9075 is the "upstream" or front sensor

234-4264 is the "downstream" or rear sensor.