I brought a S40i in 2004. I have 220,000 miles on it now. I am having trouble with the codes P0031 and P0037 and need some help.

 

 

Have you ever replaced your O2 sensors? It's recommended every 100k miles.

Did both codes appear at the same time? It's kind of suspicious when two O2 sensor codes for different O2 sensors come on at the same time. That suggests a blown fuse or broken wire. Had any work done on the top cat convertor? Turbo? Have you checked the wiring harness and connections for the top and bottom O2 sensors? (Just follow the wire loom from the sensor to the connection on the firewall) With very hot exhaust components in that area it's possible a wiring harness came loose and melted on an exhaust pipe.

 

When I started having trouble the engine light came on. Than the light started flashing and a message tell me to slow down try shift to a higher gear. I was getting several codes. PO301, PO201, P0031 and P0037.
I replaced the coil on the #1 cylinder and all the spark plugs. I than replaced the before Cat and after Cat oxygen sensors and the fuse on F33 was blown so I replaced it also..
After I have replaced all the parts. The engine light is still blinking I am still receiving the message Slow down shift to a higher gear and codes P0031 and P0037. I have not traced the wires as you suggested but I will try that next.
Thanks for your input and any more suggestions would be much appreciated.

 

This is a S40i non turbo and I have not had any work done on the Cat.