Trouble code P1521 means: Variable Resonance Induction System Solenoid #1 Circuit Hope this points you in the right direction
Call autozone and they can help with the code.
Trouble code P0715 means:Input/turbine speed sensor circuit malfunction
no sgc signal. cam position sensor
Trouble code P0401 means:Exhaust gas recirculation flow insufficient detected
po421 is catalytic converter problem rear bank
Trouble code P0720 means: Output Shaft Speed Sensor Circuit
P1601 code means there is an error on the Powertrain Control Module Communication Line to TCM PO325 code means there is a fault in the Knock sensor circuit
typemake, model, code into your computer .i have a list of codes and there is no p1105 code, clear your machine and try again
Trouble code P1526 means: Air Bypass Systemcan i see some pics of the air bypass system
The code PO404 on a 2000 Mazda Millennia 2.3 means that there is something wrong with how the vehicle is processing the oxygen it needs for combustion. This would mean an oxygen sensor or solenoid is bad. This vehicle has two oxygen sensors.
Check the toothed wheels and sensors behind the drive wheels for crud/corrosion and clean/change as necessary.