I've had a down pipe and centre decat for ages and was used to the CEL being on all the time - except when reset and then back on in several hundred miles.

Anyway, after having the PPP fitted I notice that the CEL goes off - mostly when filled with Optimax from Oxford but tend to get it back on with Optimax from other Shell garages. Thing is, I've always noticed I get better fuel economy when filling up at this Shell and better performance, so have I been lucky and found a garage with better than standard Optimax?

Also, does the CEL usually do this with PPP and downpipe decat? I had the ECU swapped when I had PPP fitted so it could be the ECU is more forgiving?



Mike

PS. This is a UK 02 WRX.

 

Could be the "exhaust gas temp sensor" triggering, when either running on a richer fuel mix, or slightly hotter than normal, like on overrun from high speed [wont suggest what scale of mph here !!].

The warning lamp has been "known" to trigger under these circumstances.

It does happen moreso when the turbo "uppipe" is changed for bigger diameter too.

It is possible sometimes to reste this with the "3 ign keyed" resets, maybe worth a try. Saves boring the dealer with constant visits. [heh,heh].

 

Sounds like the exhaust temp sensor, which might have been damaged as its bombarded with much higher temps due to the decat. Is car going in to safe mode? You can bypass the sensor by fitting a resistor under the hood: 12k 2 watt I think.