Hello to the D2 forum. Long time Disco 3 & 4 owner, but have acquired a 2002 4.0L D2 recently that I’m trying to get into shape. Runs fine, but the ‘service engine soon’ light is on. My OBD shows a P0430 cat system efficiency below threshold bank 2’ code; I’ve cleared it a couple of times but it’s here to stay. According the last owner, it cane on just as he was dropping the car off to me - make of that what you will; could be BS, but could be true (he seemed decent enough). I’ve read every post with ‘p0430’ on the forum and elsewhere and I’m none the clearer on where to start with trouble shooting. The vehicle has been very well cared for at 100K miles and runs very well - too early to tell about MPG. I’m in Ontario, and emissions testing is not required, but I would like to address the issue.

I would be grateful for any advice on where to start from those who’ve been here before.

Thanks,

 

If you aren't seeing other codes, it's most likely damaged/dead/clogged cats. How does the exhaust smell? If it's particularly stinky, this is also a sign that the cats are at end of life. You could replace them or change to straight pipes depending on your state's laws.

Mine both died due to an exhaust leak and bad O2 sensors that the previous owner ignored.

 

Maybe run a tank or two with Rislone Cat Complete Fuel, Exhaust, and Emissions System Cleaner, or similar product, following instructions. Also use a real-time scanner to monitor all four O2 sensor voltages. Monitor before and after fuel treatment to verify all is well. Cat efficiency codes get set by comparing O2 sensors, upstream vs downstream. Downstream are not supposed to swing as much as the upstream sensors.

Could also try a gallon of mineral spirits in a tank. I did that before I realized the cats had been hollowed out by the PO. I have used the Rislone product in several high mileage vehicles. I think the concept is to increase the heat in the cats to burn off or attack built-up carbon deposits in the honeycombs.

 

Thnaks. The exhaust has that weird almond sort of smell. The vehicle isn’t subject to emissions checks - if I delete the cats won’t that throw a host more fault codes? If not im up for trying it!

 

Thanks JohnZo. I’ll do some research on what cat cleaner products are available in Ontario. Worth a try.

As for reading live values what’s the most cost efficient way of doing this? I have an IID tool which is invaluable for LR3 and newer but won’t work on the D2. My OBD2 scanner doesn’t do live values I don’t think. Is there a cheap option for D2 - don’t have $000s to spend on another diagnostic tool for this one.

 

For about the cost of a tank of gas, you could get an OBD2 bluetooth plug-in (e.g. OBDLink LX), and link it to an app that runs on your phone or tablet (e.g. Torque). Even cheaper if you get a cheapo ELM327 plug-in on ebay. A good scanning set up will save you money over time, and help you enjoy ownership better. If you go straight pipe or bust out the ceramic stuff, the cat inefficiency codes might always be there.

 

I think deleting the cats doesn’t give a constant code, at least it didn’t on a Dakota I used to have. I needed to clear a CEL a couple of times a year but otherwise nothing.
An Ultragauge is a good and inexpensive choice for monitoring the engine, but it won’t do anything for the rest of the vehicle (eg ABS, immobilization etc).

 

Thanks John and Havir. I ordered a simple cabled ELM327 device yesterday and downloaded FORScan so I’ll see if I can read live values for O2 to see what’s going on.

I spent a chunk of last night reviewing the service history and noted that the vehicle did have the upper O2 sensors replaced a few years ago although no indication as to why. It seems the PO was chasing something. (I also found they’d replaced the Watts linkage, which I was about to order bushes for as I have a loud clunk, so I need to do a better job of fault finding there rather than leap to conclusions - I suspect it’s ARB related now).

Thanks for your inputs I’ll report back.