Nb CEL

[matti89]

2 months ago I purchased a 2003 mx5. Loving so far

I was driving home today and noticed the CEL come on. I got home and put the obd2 scanner on it and came up with 2 codes:
P0031 - heater control circuit low
P0443 - emission control purge valve circuit

My brief reading showa P0031 relating to the front o2 sensor. Is this the case? It there anywhere locally I can buy one and how hard is it to change? The car drives fine by what I can tell, I've never dríven another mx5 before so I'm not 100% sure. The only issue at the moment is a slightly rough idle, I'm not sure if that's because of the o2 sensor issue?

Any help is appreciated.

[matti89]

Figured out the P0443 - the purge valve electrical connector wasn't on

[speed]

Self diagnosed within the hour. I like it. Good work mate

Sent from my GT-I9506 using Tapatalk

[Okibi]

Might be time for a new O2 sensor.

[matti89]

Yea I'm thinking that aswell.

Is this the correct part?

http://m.ebay.com.au/itm/NEW-DENSO-OXYGEN-SENSOR-MAZDA-NA-MX5-PRE-CAT-4-WIRE-/302126609795?hash=item4658263583%3Ag%3ASykAAOSwXeJYGVWS&_trkparms=pageci%253A5ce0f72c-b668-11e6-afa1-74dbd180452a%257Cparentrq%253Ab1848a5f1580a2af652b596bffe72874%257Ciid%253A10

[Suspense]

Looks right, but it's cheaper at MX5 Mania.
http://m.ebay.com.au/itm/131939497290?_mwBanner=1

[matti89]

I've been having a play around with Torque Pro. I've had a short drive with it logging o2 voltages. Does this look like a normal functioning sensor? Im thinking its a heater issue with the sensor as i don't get any voltage readings on the pre cat sensor until the car is warmed up. Is there anyway i can check if the o2 sensor is receiving power to operate the heater? I don't want to buy and put a new sensor if its a wiring issue.

[thehillsarecalling]

Hmmm....can't say for sure what the stock O2 sensor behavour is meant to look like, however if I had to guess, sensor 2 is working, but sensor 1 may be a bit iffy.

Even if the sensor is working correctly, there's still benefit in replacing them in cars that have 100,000+ kms. It's common that by the time O2 sensors have had this many kms through them, they still work but often take longer to react to changes, meaning that there is a longer and longer delay between what's actually happening in the exhaust gas, and what it's reporting back to the computer (rich or lean). If you connect a WB 02 sensor to a stock MX-5 computer and then pipe the narrowband output to the computer and watch the gauge while you drive, you will see the O2 readings oscillate between rich and lean (approx 13.8 - 15.2 AFR) as you drive at a steady pace. The longer it takes for the O2 sensor to react, the worse the closed loop tune.

TLDR: If your car has 100,000+ km, it's doesn't hurt to buy a new sensor as you will probably see a boost in fuel economy for non flat out driving. This may or may not also fix your problem .