Where I live, there is a program called Aircare where each year before you can get insurance for your vehicle you have to go get it tested for emissions to make sure it is within regulations. I have a 1989 toyota pickup 22RE, and I failed yesterday! I have 7 days before my insurance expires to figure out what the problem is and get retested...

I failed for carbon monoxide emissions, my truck measured in at 1.14ppm and the limit is 0.7ppm. Interestingly enough, somebody cut the catalytic converter off my truck and stole it about 2 months ago so I have a brand new one.

Also, my check engine light has been on for a while now. I ran the diagnostic and got malfunction 21 - main O2 sensor signal. I replaced the sensor about 2 months ago but the check engine light hasn't gone away even after clearing the memory. The truck has no issues so I just ignored it and figured that it was a just another stupid light that doesn't work on a 21 year old truck...

I ran the diagnostic again today and it still has the same O2 sensor signal problem so I am assuming that has something to do with my emissions test failure. I don't know what else to do though???

Anybody has any ideas?

What brand of o2 sensor did you put in? If its a bosch go buy a denso or ngk cause bosch dont work on toyota.

21 OXYGEN SENSOR SIGNAL/OXYGEN SENSOR HEATER SIGNAL
OPEN OR SHORT IN OXYGEN SENSOR OR OXYGEN SENSOR SIGNAL

It may have been the sensor but it may have also be the wiring to the O2 sensor heater circuit. If you replaced the sensor with a proper 4-wire unit, then look into the continuity of the sensor heater wiring between the sensor and the ECU.

And BTW, a bad sensor tells the ECU to run the engine rich to prevent possible damage and rich = high HC and high CO in the exhaust.

Once you pass emissions, find someone who can tack weld a shield over your cat converter to save it from the meth monkeys. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Welcome to the board!

This sounds like it could be the culprit. IÆll check the wiring up to the ECU when I get home tonight. How should I check it?

And you have no idea how pissed I was when I started up my truck in the morning and it sounded like a 110hp Honda lawnmower after some meth head chopped my cat offà

You could use a volt meter to check for voltage at the 2 heater wires on the O2 sensor connector. It present, use an ohm meter to check for continuity on the O2 sensor heater connections.