If i fitted a decat up pipe to a 2003 wrx would the cel come on?

I have took off the 3rd (underfloor) cat already. Had no probs there.

 

yes. Up pipe contains EGT sensor. You will get a CEL code P0546 - Exhaust Gas Temperature Sensor Circuit Malfunction.

Do a search on 'CEL fix' on here, there are a couple of ways to solve this.
1. Apparently a 2.2KOhm resistor (anyone tried with success?)
2. A CEL fix kit, seems quite expensive
3. Relocate the EGT in the downpipe rather than the up pipe. Down pipe gasses run cooler and within spec of the EGT. Needs a remap to recalibrate the EGT to work as intended (richen mixture above a certain temperature)

 

Hi mate, i decatted the up pipe on my 04WRX(removing the egt) and got a cel after about 2 days. where the egt sensor plugs in i fitted the 2.2ohm resistor, started 5 times and all ok. was ok until i sold it about 3months later no probs.

Cheers
Lee

 

If you remove your uppipe cat you will get a CEL. Check out this thread, Uppipe FAQ: Read if you are thinking of buying one! - NASIOC.
It explains how to do the up pipe CEL fix with a photo. I did it in about half an hour. I've kept the sensor in the garage in case I go back to standard sometime. You just need to tape up the connector with the resistor in it.

 

Just to let you know, I asked Harvey (fine chap !) and he directed me to Hayward and Scott for a wrx up-pipe CEL fix.

Just phoned them, very helpful 10quid for CEL fix, posted same day.

Hayward and Scott : 01268 727256

Hopefully this will work for up-pipe CEL. Can't get rid of downpipe CEL as easy, my remap will sort that next week.