Q: 2004 Mazda 2 DY3W ODB II reader error codes P0031,P0841,P0351,P0733,P0715....what needs to be repaired?

I will explain each code in turn. To resolve all codes, the recommended service to request is a check engine light diagnostic. If you request that service, the responding certified mechanic will get this taken care of for you.

P0031 sets when a fault is detected in the circuit that powers the oxygen sensor heater in the Bank 1 upstream oxygen sensor. That is a fairly straightforward problem to diagnose and resolve (heater might be bad, in which case you need a new oxygen sensor; not unusual).

P0351 is due to a malfunction in the ignition coil primary or secondary circuit. The engine control module is looking for specific signals from the ignition coil and when these signals are not detected the ECU sets the Check Engine Light. Detailed causes include faulty spark plugs or plug wiring, a defective ignition coil, failed or failing ECU, open or short in the coil wiring harness, or poor electrical connections.

The remaining three codes all relate to the transmission. Check the level and condition of transmission fluid as that is implicated in all three codes. P0841 is usually caused by either a faulty electronic pressure control solenoid in the transmission or there is a fault with the transmission fluid pressure sensor. Other possibilities include blockages inside the internal transmission hydraulic fluid passages, low transmission fluid, dirty or contaminated transmission fluid, mechanical internal transmission failures, or a faulty PCM or transmission control module but those are rare.

P0715 usually has one main cause and other secondary issues that are less common. The full slate includes: faulty transmission speed sensor, faulty or damaged speed sensor wiring, faulty speed sensor electrical connection, faulty shift solenoids, damaged transmission valve body, or dirty or low transmission fluid.

Finally, P0733 is caused by a faulty shift solenoid, a faulty powertrain control module, a faulty transmission module (if applicable), low or dirty transmission fluid, debris inside transmission causing a restriction in the flow of transmission fluid, or internal transmission damage.