Drove home from work the other night and my cel came on like it does every now and then from freeway driving cause i have header and d/p no cat. Got up to go to work yesterday pulled the battery cable to clear the cel. Start the car and for the first 2 secs it seems fine then the cel comes on and the rpms start fluctuating and getting smoke out tail pipe then after the warm up the rpms drop to 500 and bounce between there and 300 almost stalling. gonna try and pick up a scanner today. Got code scanned p0420

Mods I have are: Fujita CAI, RRM udp, RRM piggy back, RRM Header D\P.

 

Disconnected my rrm piggy back ecu and the car started fine. No more cel no more limp mode.

 

Has anyone had there car go into limp mode cause of p0420?

 

p0420 means the two o2 sensors in your exhaust are similar meaning the cat isnt functioning properly.

make sure your exhaust isn't leaking and your cat is working.

as far as sending your car into limp mode im not sure.