Failed E-check

Where I am living right now, the cars have to pass an emissions check before you can get your tags/plates.

My 2000 Malibu really failed hard. I haven't a clue where to find out what the codes mean.

P0135 02 sensor Heater circuit malfunction. (Oxygen sensor?)
P0404
P1404
P1635

I guess the first one is the oxygen sensor - where is this located?

I found the codes.
http://www.2carpros.com/kpages/diagnostic_trouble_codes.htm


P0135 Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

P0404 Exhaust Gas Recirculation Circuit Range/Performance

P1404 Exhaust Gas Recirculation (EGR) Valve Pintel stuck open.

P1635 5 Volt Reference Circuit

Can somebody tell me what these mean??

Do not replace your O2 Sensor just yet!

Your problem seem to be the EGR Valve... This valve recirculates CO2 gases from the exhaust pipe back to the intake and burns them a second time to reduce polutants. This EGR Valves have a tendecy to plug the valve orifice (Valve Pintel stuck open) with carbon biuldup, crud, etc. and giving the engine an overdose of CO2 emissions causing the codes you're having.

You'll need to remove the EGR Valve and give it a good clean and also unplug the hole (orifice) on the manifold so the air (hot CO2 gases) can move freely!

The reason you're getting a "P0135 Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)" code is because the air/fuel mixture is wrong because of the EGR Valve getting stuck open and causing the O2 Sensor to have a bad reading, once the problem is fixed the o2 Sensor code should go away! That's why I'm advicing you not to replace it yet!

I agree, pull the EGR and clean it out. I have a '99 malibu (3.1) and it is really easy. The EGR is right on top, two bolts and it's off. I use some small brushes and a can of brake parts cleaner to scrub and rinse it out. Just make sure the pintel moves freely and easily returns down when pushed up. With 226k on it, I cleaned mine out about two years ago and it's still going fine (EGR valves are quite pricey for what they are.)

The heated o2 code is not related to the egr issue, the fuse is blown for the sensor or the ground is bad or the sensor is bad. The heated portion of the o2 is not connected to mixture feedback to the pcm, it is entirely different circuit.