slumapas

So I hooked up the Durametric and read the voltages for all 4 O2 sensors and the lambda values for banks 1 and 2. The voltages started in the 4+ volt range and went down to less than 1 as the vehicle warmed up. The lambda seemed to stay around 1 volt the whole time with very slight fluctuations as the vehicle ran. It looked like everything was tracking at this point. I cleared the errors this morning and the vehicle seemed to still run fairly well all day, but while cruising down the freeway at 63-65 mph this evening the check engine light popped up again with only the two errors: P0421 Catalyst System Efficiency Below Threshold Bank 1 - Upper limit value exceeded, test conditions are not-completed, fault is not currently active and causing a DTC light P0431 Catalyst System Efficiency Below Threshold Bank 2 - Upper limit value exceeded, test conditions are not-completed, fault is not currently active and causing a DTC light I'm leaning even more towards faulty cats. Should I try and read the live values on the Duramertic? I honestly wouldn't know which values to monitor so if that's the case some guidance would be much appreciated. Thanks all...

Thanks for the reply. I will check tonight with the Durametric, Since all 4 sensors are new and it's happening to both banks could I have an issue is the wiring harness leading up to the sensor plugs? Or could it be something else more centralized like the ECU? Any thoughts on the cats themselves?

Good evening everyone, I've made several searches but I haven't run across one that addresses this specifically or has a resolution. Here goes: Our new to us 2005 Cayenne V6 3.2L, 6-speed manual w/ 91,700 miles (we bought it with 82,000 miles) runs great and has given no problems for the first 6-8 months of ownership. It then gave a random CEL which I read with the Durametric to be: P2237 Lambda control adaptation at idle, Bank 2 - Upper limit value exceeded, test conditions are not-completed, fault is not currently active and is not causing a DTC light P2237 Lambda control adaptation at idle, Bank 2 - No signal/communication, test conditions are not-completed, fault is currently active and causing a DTC light P2235 Lambda control adaptation at idle, Bank 1 - Upper limit value exceeded, test conditions are not-completed, fault is not currently active and is not causing a DTC light P2235 Lambda control adaptation at idle, Bank 1 - No signal/communication, test conditions are not-completed, fault is currently active and causing a DTC light I reset it once, switched gasoline stations (using premium 91-92 at all times) and it comes back about 4 weeks later. I change the gas cap, reset it and it comes back 3 weeks later. Searched forums and was basically looking at replacing my O2 sensors. Replaced the pre-cat sensors, cleaned the MAF and reset. CEL returned 2 weeks later. Replaced post-cat sensors and found a couple of the plastic vacuum lines had cracked next to the intake manifold. Repaired the vacuum lines, reset the CEL and it went away for almost 3 weeks. Unfortunately the CEL came back with this: P0421 Catalyst System Efficiency Below Threshold Bank 1 - Upper limit value exceeded, test conditions are not-completed, fault is currently active and causing a DTC light P0431 Catalyst System Efficiency Below Threshold Bank 2 - Upper limit value exceeded, test conditions are not-completed, fault is not currently active and causing a DTC light So now I'm thinking catalytic converters but I do a bit more searching and one thread mentions that for catalytic converter to fail so early something may be causing it to fail. So now I've replaced the MAF and plugs (mainly because I don't know when the plugs were replaced last), reset CEL and it came back 3-4 days later with all of the codes: P0421 Catalyst System Efficiency Below Threshold Bank 1 - Upper limit value exceeded, test conditions are not-completed, fault is currently active and causing a DTC light P0431 Catalyst System Efficiency Below Threshold Bank 2 - Upper limit value exceeded, test conditions are not-completed, fault is not currently active and causing a DTC light P2237 Lambda control adaptation at idle, Bank 2 - Upper limit value exceeded, test conditions are not-completed, fault is not currently active and is not causing a DTC light P2237 Lambda control adaptation at idle, Bank 2 - No signal/communication, test conditions are not-completed, fault is currently active and causing a DTC light P2235 Lambda control adaptation at idle, Bank 1 - Upper limit value exceeded, test conditions are not-completed, fault is not currently active and is not causing a DTC light P2235 Lambda control adaptation at idle, Bank 1 - No signal/communication, test conditions are not-completed, fault is currently active and causing a DTC light So I'm back at the catalytic converters again which I'm fine with doing, but here are my questions: 1. Do catalytic converters fail this soon on a low mileage vehicle? 2. Why would the P2237/2235 codes come back? 3. Any ideas on what I may be missing? More vacuum leaks, ECM issues, etc? Lastly as a side note, when changing plugs, I inspected the coils and they all looked fine (i.e. no obvious cracks, wiring in good shape, etc) but I did notice small oil build up on the top of the plugs (none in the cylinders - plugs looked normal). Is that indication of a leaky valve cover gasket and would that be related to any of my issues? Sorry for the long post - just wanted to be thorough. Any help or insight would be greatly appreciated. Thanks everyone...

I don't know if your question was answered, but I also underwent a small coolant leak on the driver's side where the temp sensor is at. The issue appeared to be the blank plug next to the temp sensor. Over time the plug developed a crack and started to seep right down the center of it. The coolant flange appeared to be in good shape still. The part was under $3 from my local import parts dealer and I lost about 1/3rd of a Liter of coolant during the plug change. It's a bit tight getting back there, but not too bad. I ended up using a full liter of coolant to reach the max in my reservoir. So far so good--no more leak--I'll update if there is any changes.