04 6MT Blown ECU???

[mecjacob]

Hey guys, newbie here with a question. I had a good running 04 rx8 manual and then all hell broke loose. I installed a boost brothers header. Good quality and fit. I couldnt get my oxygen sensor out of my old manifold so I left it and ordered a universal 4 wire sensor. I plugged the hole in the header and drove it home to wait for the new sensor. It drove fairly good although seemed pretty rich (understandable having no 02 sensor). I parked it and waited for my new sensor. So my new one came in and I spliced the wires together. I did do research and spliced the correct ones. I then started the motor and it is so rough it barely runs. Im getting a trouble code P0130 which is the oxygen sensor circuit malfunction. So I unplugged it and its the same story. Barely idles. I also suddenly have 4 incomplete MIL's the seondary air, catalyst, o2 sensor, and EVAP. I checked the voltage in the front 02 sensor plug with the key on and it shows .2 volts??? Thought it should be 5v. But if I check the voltage in the plug and use a vehicle ground and not the sensor ground it shows about 2.5 volts. Is it possible my new sensor sent a volt or 2 to something that it shouldnt of like the ECU and fried it? Or is it more likely that I have an open ground somewhere? Im completely baffled and really hoping someone can help. Thanks...

[chickenwafer]

More than likely you installed the new o2 sensor wrong. The OEM sensor is a wideband 5v sensor, brand new it's about $250 from Mazda. You need to install it or just drive around with no front O2 sensor and be stuck in open loop and get horrible gas mileage.

[mecjacob]

Thats kinda what I thought. Although it is pretty easy to install it correctly unless it is just not a compatible sensor. But my big concern is that after I removed the new sensor and just plugged it back up it still runs like it did after I installed the new sensor, horrible. And Im not even getting 5v to the sensor plug on top of the bell housing, only about 2.5. So is it possible that putting in a non compatible sensor ruined my ECM?

[Flashwing]

I doubt that you've done any serious damage to the PCM which would cause it to self destruct or anything like that.

As much as I favor doing some of the generic stuff, you would honestly be better off getting an OEM O2 sensor.

Is the sensor you purchase a wide band or a narrow band? The RX8's primary O2 is a wideband sensor. You might be better off getting one from the dealership which would be plug and play. If it's a generic narrow band the PCM is going to have a fit.

In either case, when you get a new sensor hooked up just be sure to do a PCM reset. Disconnect the battery, press the brake pedal for 10 to 15 seconds to totally drain any power and let the car sit for maybe an hour to reset all your fuel trims that would have been created from the faulty sensor.

With that and a new sensor you should be right as rain!

[chickenwafer]

You really only need to disconnect the battery and let it sit for about 5 min, and touch the positive and negative battery cables together (OFF the battery!) to discharge any store electricity and clear all the sensors and trims.

Install a fresh OEM wideband and you should be good to go. I know it sucks how the factory cross-threads a lot of those widebands, I was luckly in mine came out, but I knew the tech who did my motor swap for me at the dealership ;)

[mazdamaniac]

You really only need to disconnect the battery and let it sit for about 5 min, and touch the positive and negative battery cables together (OFF the battery!) to discharge any store electricity and clear all the sensors and trims.

It does take over 20 minutes for the caps in the PCM to discharge and eliminate the NVRAM.
Touching the battery terminals doesn't quite do the same thing as pressing the brake pedal, BTW.

[mecjacob]

Thanks guys. I didn't realize it was wide band when I bought the narrow band. It didn't even cross my mind probably because its rare to hear of a wide band being stock. kinda confusing why it even is. Thanks for all the help...