FRaMist

Thanks! Excellent advice! Answers: No, a live data scanner was not used on the cats. No, the codes have not been cleared manually to see when they return. (The SEL stays on from Ignition through trip). I have a new tank of Premium fuel and the car runs so smoothly that it's hard to believe the engine light is on! I saw a great pair of videos by a mechanic/owner and learned that the slow start and lag in performance when you start out from a stopped position, or in first gear (automatic) a low rpm is directly related to the knock sensor in his case. The part is on order, as suggested, from Amazon. My mechanic has agreed to install it and do the diagnostic on the cat system, clear codes, to make the right call on the O2 sensors. Many Many thanks. I'll update what I find out.

Greetings! I think I've figured out where to post this on the forum. I am a brand new Subaru owner. 1997 Legacy Outback Wagon with standard engine. I love it. 232K miles, and two codes for the SEL prevent me from passing inspection in NJ P 0325 Knock Sensor Circuit P 0420 Cat Efficiency Bank 1 The knock sensor is seems fairly straight forward. I will replace it and hope the code goes away. At first, I thought I would have to replace the whole catalytic converter...but I got advice here NOT to do that. The mechanic I hope to trust here said that the P 0420 (which he knew off the top of his head) would NOT BE CLEARED by replacing the O2 sensors as a few experts here previously suggested. He says a flush of the cat system would clear the code temporarily, but that the CAT EFFICIENCY reading implies that the two sensors are working, and the cat is clogged. His price is around $170 for chemicals and labor and he thinks that the code will clear in order to pass inspection. Advice is welcome. I like the idea of the price for the one year of inspection, I'll prove that the O2 sensors work and save up for a new Cat system later. However, with the knock sensor code, it does seem interrelated according to postings here. I don't know which road to travel? Nearly broke, but must get the car passed the NJ state inspection system which is entirely code-based. Sincerely! Erik

FANTASTIC ADVICE!!! Thanks so much. I'll start with the O2 sensors and work in that order. Much obliged.

I have a brand old Subaru that will not pass NJ inspection because of a [ P 0420 Cat efficiency bank 1 ] code from the engine light being on. A mechanic friend and 3rd party who work at Subaru suggested I replace the whole Cat system, front and rear to clear codes and start fresh. Car has 232K miles. Must clear codes to pass inspection in NJ. What is the best after-market value considering quality and price over the OEM list. I have seen the whole unit for around $250, and as much as $1014. I'll probably buy what you tell me to, so advise well! The car run extremely well, and I only paid $675, so there is a little budget to get her to another 100K Thanks so much, Erik

Dear All, First week of being Subaru owner. I got a great deal on a 1997 with 231K miles. The CEL is on, and has been on for at least 4 years according to previous owner. The code is P 0325 Knock sensor circuit Does this mean that there is an engine knock, or that the sensor is bad? How can a mechanic tell the difference. The head gasket was replaced at 131K (100K ago) and I don't know what else the knock sensor code is telling us. I cannot afford much, so am nervous that the car will not pass NJ inspection without major engine work. The catalytic converter will be enough of an expense, but easy to understand. If you can advise me on what the knock sensor code likely means, please do so. Thanks! It fails inspection also because of P 0420 Cat efficiency bank 1, but that is fairly straight forward. I would like to know if it is front or rear, but probably best to go ahead and change out both.