check engine light help

[localkineguy]

Hi guys,
I have a 2003.5 Protege5 that has recently given me a CEL with two codes. One is a P0090 fuel pressure regulator circuit 1 and the second is a _____ (can't remember the number), which is about the catalytic converter temperature being below threshold.
The car drives feels fine driving except that the engine eats oil like 2 quarts per gasoline fill up.
I've cleared the code once and it came back on. Both times the CEL have come on, my girlfriend has noticed no change in the car's driving.
Thoughts?
Thanks

 

[north42g]

The p0090 is likely the PRC. [Pressure Regulator Control-valve] This code is telling you that there is an electrical issue with that circuit. locate the Fuel Pressure regulator Control solenoid valve. Inspect all around for loose connector, frayed or disrupted wires, anything that may cause a bad connection. The Solenoid Valve is likely the culprit and will have to be replaced. -It may be a Dealer Only Part.
Could be a connector or terminal malfunction.
Could be Short to ground in wires between PRC valve terminal B & PCM terminal 95....
better yet: UN plug your connector and check for power and ground. If you have power & ground then replace PRC Solenoid Valve.

The latter is likely a DTC P0421 catalyst efficiency below threshold, bank one - possible failed Catalyst or Failed Post - Cat Ho2S[Heated oxygen Sensor]

 

[localkineguy]

Within the last 6 months, I've had a P0090 code flash and had that circuit checked and some wiring replaced ($150, since when does wire cost $150?). Where can I find the solenoid valve?
Regarding the DTC P0421, it flashes simultaneously with the P0090...why would they be related?

 

[tweety2300]

If your precat is bad or the o2 sensor it will be on anyway. The precat is very sensitive and fails easily. I can't help with the prc but going through that much oil is rediculous do you have any noticable. Leaks? Do you have oil in your coolant?

 

[igdrasil]

If you have the time and tools available, test compression leaks for stuck piston rings, blow-by gases will liquify and evaporate oil faster.

Replace your recirculation valve if its bad (top of valve train cover, I think is the "PCV valve, checkvalve..."), this can cause the latter oil to go inside engine cylinders and damage oxygen sensors, this will in turn make the ecu send the code for the oxygen sensors being erratic or out of range.