I have 1997 Ford Taurus just failed emission test with the codes of PO401 PO455.

Question

failed emission test with codes PO401 and PO455 service engine soon light is on. What could be the problem?

Answer 1

P0455 is related to the EVAP system 

Try to replace the gas cap with a factory gas cap first. if the problem is still there check the EVAP system for broken, cracked or loose hoses.

 

P0401 is most likely a clogged EGR valve and its piping. Try to clean it first.

Possible causes

- EGR passage clogged

- Faulty EGR Vacuum Modulator Valve

- Faulty EGR Valve

- Faulty EGR solenoid valve

- EGR solenoid valve harness is open or shorted

- EGR solenoid valve circuit poor electrical connection

- Dead (Weak) battery

- Faulty EGR temperature sensor and circuit

- Exhaust gas leaks