CEL after Gutting Pre-Cats - O2 Sensor Spacers?

[cobraBLACK]

I realise this has been covered several times but I've looked back through several threads and need to clear something up before my MOT test on Friday.

Do O2 sensor spacers actually work?

If so, where do they go? I presumed they would be for the sensors after the pre-cats but one thread suggested they should be after the main cats.

Can anyone definitively clarify it for me please?

[VinnysS4]

02 spacers or "spark plug non foulers" work by removing the O2 sensor out of the air stream. Yes they work (moat of the time) Some companies use a piece of tubing bent in a j to pull the O2 out of the air stream. Sometimes you'll need several spacers stacked to eleminate a CEL. I've even seen guys screw their O2 sensors into the frame of their car/truck.
The first O2 sensor (or air to fuel senor) is the sensor your ecu uses to determine if the engine needs to be "trimmed". By that I mean your fuel trims. ( Add or subtract the fuel based on readings of this first O2 sensors.)
Your second sensors are there to monitor the effectiveness of your cat it sits behind and to make sure it's doing its job. When you.hollow out the cat before the sensor, your sensor throws a CEL. If you can remove the sensor out of the exhaust air stream, or move the O2 to before the cat, you should be fine. That or get a tune that codes them out.

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[greg.rutland.54]

I just gutted my pre cats last weekend. Same thing as you I got the CELs. Luckily I already bought the o2 spacers off amazon. 1 angles and 1 straight so the don’t hit each other. You’ll have to separate one side from the cat back to lower it to put the angled one on. Drive shaft is in the way.
CELs are gone.

Also the go in the rear sensors. Which are directly behind the main cat.




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[cobraBLACK]

Perfect. Thanks, guys.

[kabukie]

I used the longest spacers that was sold at the local auto parts store. Worked great.

Ended up going with a JHM tune and now don’t need them

[mad70sx]

I got CEL's after installing a set of JHM downpipes. Tried various spacers (long, short, angled, straight) but none seemed to work for me. The only way I could get rid of it was with JHM's tune.(which I was getting regardless) If the spacers don't work you may need an ECU tune to get rid of it.