I really have a love/hate relationship with this temperamental teenager with 135K miles. 2 years ago I posted here about my battles getting the oxygen sensor monitor to reset to allow me to pass smog. Eventually after some combination of replacing one oxygen sensor, a bottle of Guaranteed to Pass and my wife driving the car outside of its normal routine did the trick. I've been experiencing the same trouble this time and now the tags are months expired although I did pay the registration fee and keep paperwork in the car to tell my story if needed. I went through the drive cycles multiple times. On top of this, my scanner - iCarsoft 2 has quit cooperating and now will not connect at all. I asked about similar experiences in a separate post.

Now, after all this time and a suggestion, I decided to replace all 4 oxygen sensors. I like to think I am past semi blindly throwing parts at a problem but figured it was worth a chance here. When I could scan, I never got a code indicating a problem with them but figure they are parts that do eventually need replacing and it was worth trying now.

So, I replaced all four and started getting just about every possible issue. At first, got air suspension fault/ vehicle too low and a check engine light. Not being able to scan, I went to O'reilly and a helpful worker there who seemed kind of excited to scan a car a little fancier than normal scanned it and got P0420, P0036, & P0134 - all related to bank 1 cat & sensors. I quickly figured there was an issue with how I plugged in the new sensors and got underneath and remedied that. Neither plug was fully seated.

With that done, I've still gotten a bunch of warnings that have come and gone.
Check engine went away pretty quickly and I have not scanned again.
Air suspension/vehicle too low happened again but was gone most recently - I think this could be related to jacking the car up to replace sensors. It takes a while to get its bearings again.
Restricted performance - I had gotten this a couple times before this adventure. Back then, it was after freeway driving which I did not do yesterday. I understand it's probably related to supercharger cooling which is the first thing I'll address after resolving current issue.

Having said all this and with all of these faults/warnings, I am considering resetting the ECU. I've never done it but figure this might be the time for a fresh start with all new oxygen sensors.

Thoughts on doing it or waiting and hoping everything resets sooner rather than later? What are the downsides to a reset?

Any input greatly appreciated

 

I doubts the SC cooling has much to do with any of your faults.

Possible a bad cat coverter, blocked maybe, or bad wiring to an oxygen sensor.

I have never heard of anyone not being able to "seat" the sensor plugs. So did you "stretch" the sensor wires and damage them?

Also at 135k miles if your SC coolers have never been cleaned they are very likely to be at the very least partially clogged with soft carbon build up.

 

By "seated" I meant plugged all the way in and the lock tab in place. Age and heat on a relatively delicate plastic plug doesn't make for the most positive connection. The check engine light going away right after makes me think that was one issue remedied.

 

Agreed.

 

Thanks for the responses. I just went out for about a 5 mile drive. I’m now getting:

no Check Engine light

Air Suspension Fault but no Vehicle Too Low - From past experience, this comes on when the compressor is ruining excessively. I had this a few years ago and replaced the seal in the compressor and all has been fine until now. The least of my concerns right now

Restricted Performance- I think I am understanding there are different degrees of this and this is unlike my past supercharger/freeway issue. In that instance I believe top speed is governed down to about 70 mph but nothing else affected. I read on another thread about O2 sensor issues and in that case the engine kind of pulses in maybe a limp home mode? I am getting pulsing so that may be my case here.

I’m still considering the hard ECU reset but still concerned about any possible negative effects.

 

Touching the battery cables together, when disconnected, will "reset" almost everything.

Only possible side effects will be having to re apply some things that were originally programmed in such as window opening settings or mirror settings etc.

Nothing dramatic. Fault codes will be reset but not actual faults of course.

 

Thanks, I'm leaning towards doing it this afternoon. I saw a video on a '90s era Jag and a code was needed to reset or remember certain things. Any idea if that's needed for this generation? I should have it anyway and will check my paperwork.

 

My 2005 XJR did not need any code.

Electronics changed between 2005 and 2006 but have never seen anyone say that a code is required. A code used to be required for radios however that was a while ago.

 

The radio rest was what I saw. Thanks

 

I did the reset and it was easy as described and all memories were saved automatically. It did erase the codes etc. but I still have issues. I still have the uneven idle but no codes or restricted performance warning - yet.

I consulted someone locally, explained the situation and his first question was "Did you use OEM O2 sensors or cheap Chinese stuff?" It was the cheap stuff. He advised me to replace with the good ones and things will likely work themselves out. That's my next action so I ordered upstream Densos and downstream Bosch. Hopefully this will be lesson learned.