Hapich

I had my O2 sensor replaced and I have driven over 150 miles but the cat sensor won't read so I can't pass smog. How many miles do I need for the darn thing to reboot?
I'm going to drive another 100 first thing tomorrow. Hopefully it will read after that.
Rob

Ahsai

I assume you meant the O2 sensor test readiness is not set yet. You may need to drive a few more cycles as opposed to longer distance. Cycle meaning the car starts from cold. You may need a combination of local and highway traffic. For normal cit + highway driving, my experience is the O2 tests are pretty easy to set in a couple of days.

If you're talking about the Cat test readiness, that may take longer like a few days to a week.

Hapich

Thanks for the input. Appreciate it

5CHN3LL

Is the check engine light on? Are you showing any OBD-II codes? If you have diagnostic codes related to the O2 sensor, the car will never be emissions-test ready.

If things are working OK, completing a drive cycle will get the car ready for emissions inspection. If there is an issue with the new O2 sensor, another hundred miles won't help.

Unless all 150 miles were at a set speed, with no variation, it's hard to believe that driving that far - which should probably have taken at least a couple of hours, right - would not have satisfied the "drive cycle" requirements...

Macster

150 miles is based on my experience about 5X the number of miles necessary to have the DME complete all readiness monitor tests, including the O2 sensor and converter performance tests.

Be sure you aren't hammering on the car/engine. The DME needs just plain old driving, a combination of cold start, some idling, steady speed cruising, some highway speed time. More than once I have cleared an error code from my Boxster's DME and driven to work -- 30 miles and the drive very much like I described above -- and have had all the readiness monitors set to complete upon arrival.

Hapich

I've put 300 miles on it in all conditions and about 8 different trips in a week and a half and the it still reads the cat sensor "not ready". I'll try for a couple more days and then I'll have to ask my shop what the heck is up with it.

Hapich

No codes. It's running like a top. 8 trips between 100 and 20 miles, 300 total. Scanner still saying cat sensor "not ready". I'm going to have to call my shop. I'll give it 2 days then Sat it's going back.

Ahsai

That is strange indeed. Let us know what the shop finds.

DBJoe996

Frankly speaking I would not drive it more miles to see if it clears. Obviously there is a problem with the O2 sensor. Maybe it is a bad one, maybe they forgot to plug it in or did so incorrectly. First, get an OBDII code reader and check for codes. If that is not possible almost any local auto store will help you check for codes and clear them. Second, remember the DME is using feedback from the O2 sensors to determine air/fuel mixture. Not saying this is a huge problem but with unstable or no read from the O2 sensor the rich/lean air fuel mixture is upset and could possibly create an inbalance of mixtures between banks. At a default level, a no read from the O2 sensor might be telling the DME that it is not up to temperature resulting in a constant rich cold engine mixture even with the engine up to temperature. That will flood your cylinder bores with too rich a mixture at operating temperature, and will wash the thin layer of oil from the cylinder walls. More driving is not the solution. An O2 sensor is a relatively simple device and this should be an easy problem to fix.

Sneaky Pete

I have no comment other than I tried to read Schnell's response but his flashing avatar dove me into a seizure.

DeanClevername

I just spoke with a mechanic about resetting this and he recommended a drive cycle, BUT he also recommended draining the ECU's capacitors beforehand. His instructions were to disconnect the battery and then (a safe distance away from the battery terminals) touch the CAR's positive and negative leads together for about a minute.

Something about this makes me nervous, but some googling shows this is a relatively known technique. Anyone tried this?

dansen

Hi Hapich, I have the same problem like your. Actually, I replaced all 4 O2 Sensors after SMOG said Cat not ready. One of the sensor looks pretty bad. I drove 400 miles and it is still cat not ready. It looks like I need a new cat. What happened to your?

Hapich

I realize this is a zombie thread but I have an update and it's not great. My Porsche shop replaced another O2 sensor and told me that the computer finally picked up the catalyst. Then he got it smoged next door. Great right? So I put my code reader on for the hell of it, first time since the cat reading problem, the other day and guess what. The cat is still not reading!!!! I didn't check it after the work was done because it never dawned on me. So those jerks got it smoged somehow and didn't fix the problem. I have only been driving it about 20miles a week so hopefully that's ok. It runs great. I'm sooo pissed at them and myself!!!! I will never go back to those clowns. I'm going to try a place in Downey, Westwerk. Has anyone used them? I live in Long Beach CA.