I have an 04 Mazda 6 and the check engine light came on about a week ago.

It hasn't gone off, so I went to an autoZone and had them run the codes on it, it spit out the following codes:

P0431
U0155
U0100
U0121
U0101

The car runs fine and I've had no problems with it at all. All of the U-codes said that they were related to communications. Anybody have any idea what's going on??? Let me know if you have any ideas...

 

how long have you had your car? and how many miles are on it?

 

the P431 code is the heater for your o2. which may not be an issue. this code can pop if you try to drive the car prior to the O2 hitting operating temp.

the U codes are point to a couple things, loss of communication to the ECU, and the instrument panel. our system is multiplex so the error can take place anywhere in our electrical system.

Have you had the MSP10 recall performed on your ride yet?

try disconnecting the battery, press the brake for 30seconds, reconnect the battery, and drive the car. see if the CEL comes back

 

I have not had the msp10 recall yet...but I've heard from others that it might help. The car has 130000 miles on it, but it is mostly highway. I've only had it for a couple months.

I'll try disconnecting the battery and then pressing the brake and seeing if it goes away. I'll keep you updated.

 

I just checked with a Mazda dealer and I have had the MSP10 recall done already.

 

I disconnected the battery and held the brake, light came back on a day later.

What steps should I take next??