I failed my smog test two years ago with the "check engine" light on. I replaced the oxygen sensor and passed. Now, with one month before my next smog test is required, the "check engine" light goes on again!
I don't think it's the oxygen sensor, so how do I find out what is causing it? Or do I take it to the smog check place and fail, so they can tell me why?
Your 97 Celica is OBD-II compliant. If you have a scan tool, use it. If not, take it to AutoZone or similar, have them put their scanner on it, and get the code(s) coming up on the scanner and let us know what they are.
exactly, a lot of places offer a quick free OBDII check engine light test. Make sure to get the actual code number from them. Sometimes the scanners can be overly vague or too cryptic
First, some clarification. Both Autozone and Kragen said that California law prevents them from doing scanner checks. Since Pep Boys also provides a service bay, I called them and they agreed to do one for free.
Here's the code that they found:
P0130
Anyone know what that means, or how to decipher it?
P0130 - 02 Sensor Circuit Malfunction (Bank I Sensor 1)
What does that mean?
The O2 sensor produces a voltage based on oxygen content in the exhaust. The voltage varies between .1 and .9 Volts, .1 indicating lean and .9 indicating rich. The ECM constantly monitors this voltage while in closed loop to determine how much fuel to inject. If the ECM determines that the O2 sensor voltage was too low (less than .4 Volts) for too long (for more than 20 seconds (time varies with model), this code is set.
Potential Symptoms
Depending if the problem is intermittent or not, there may be no symptoms other than MIL (malfunction indicator lamp) illumination. If the problem is constant, then symptoms may include one or more of the following:
MIL illumination
Engine runs rough, missing or stumbling
Blows black smoke from tail pipe
Engine dies
Poor fuel economy
Causes
Usually the cause of P0130 is a bad oxygen sensor, however this isn't always the case. If your o2 sensors haven't been replaced and they are old, it's a good bet that the sensor is the problem. But, It could be caused by any of the following:
Water or corrosion in the connector
Loose terminals in the connector
Wiring burnt on exhaust components
Open or short in the wiring due to rubbing on engine components
Holes in exhaust allowing unmetered oxygen into exhaust system
Unmetered vacuum leak at the engine
Bad o2 sensor
Bad PCM
Possible Solutions
Using a scan tool, determine if the Bank 1, sensor 1 is switching properly. It should switch rapidly between rich and lean, evenly.
1. If it does, the problem is likely intermittent and you should examine the wiring for any visible damage. Then perform a wiggle test by manipulating the connector and wiring while watching the o2 sensor voltage. If it drops out, fix the appropriate part of the wiring harness where problem resides.
2. If it doesn't switch properly, try to determine if the sensor is accurately reading the exhaust or not. Do this by removing the fuel pressure regulator vacuum supply briefly. The o2 sensor reading should go rich, reacting to the extra fuel added. Reinstall regulator supply. Then induce a lean condition by removing a vacuum supply line from the intake manifold. The o2 sensor reading should go lean, reacting to the enleaned exhaust. If the sensor operates properly, then the sensor may be okay and the problem may be holes in the exhaust or an unmetered vacuum leak in the engine (NOTE: Unmetered vacuum leaks at the engine are almost always accompanied by lean codes. Refer to the appropriate articles for diagnosing an unmetered vacuum leak). If the exhaust does have holes in it, it's possible that the o2 sensor may be misreading the exhaust because of the extra oxygen entering the pipe via those holes
3. If none of this is the case and the o2 sensor just isn't switching or acts sluggish, unplug the sensor and make sure there is 5 Volt reference voltage to the sensor. Then check for 12V supply to the o2 sensor's heater circuit. Also check for continuity to ground on the ground circuit. If any of these are missing, or aren't their proper voltage, repair open or short in the appropriate wire. The o2 sensor will not operate properly without proper voltage. If the proper voltages are present, replace the o2 sensor.
The Following User Says Thank You to 93celicaconv For This Useful Post:
For some reason, my check engine light went off and I took it to be smogged. Apparently, during the test, the light came back on and I failed. The tech said that I needed a new sensor, even though I bought this one two years ago. He blamed the two wires I didn't connect (the original was two-wire, the replacement was four-wire).
I have two questions...
1) Does the two-wire vs. four-wire reason make sense?
2) Where would be a good place to order a two-wire sensor online?
Just because the CEL went out doesn't mean the ECM isn't storing the code as pending. And it is. That is probably what the tech found when putting a scanner on it. I don't think you can pass an inspection with any kind of active or pending code in the ECM.
So if the original O2 sensor was a 2-wire version, how did you connect your 2-wire wiring harness to the 4-wire connector on the O2 sensor you bought 2 years ago?
The 4-wire O2 sensor is one that uses a heater to come up to sensing temperature faster than a non-heated sensor.
I would think an automotive parts store would have the proper sensor for you. Such as Advance Auto Parts has a Bosch O2 Sensor, Part No. 12109, an OE 2-wire unheated upstream (pre-cat) sensor for $70.99. They are readily available.
PS: The 4-wire O2 sensor for your car is a downstream (post-cat) sensor, which is a heated O2 sensor. I think when you got your new O2 sensor a couple years ago, you bought a downstream O2 sensor for an upstream application. I wouldn't have thought that would have worked at all, but I guess the only difference is one is heated and the other is not? Might want to keep your old 4-wire O2 sensor, just in case your post-cat sensor ever dies.
I don't know anything about SNG. I have used both Bosch & Denso (Denso on Toyotas, Bosch on other makes), and so far, I haven't had to change a replaced unit out on any of these, so both seem to work quite well. If you can get a Denso for about the same cost as the Bosch, I would probably have a slight perfernece going that way.
You will need to clear your ECM code after the change, however. If you know someone who has a scanner, or can get the place you get the O2 sensor from to do it after you make the change (sometimes they will do that, but maybe not in Cali). Otherwise, you will have the same problem going to the inspection. It takes something like 60 consecutive good cycles to clear a code in ECM memory on OBD-II systems, and you don't want to wait that long.
You still have me stumped on how you got a 4-wire O2 sensor to work with your 2-wire connector on your pre-cat location though. That's OK, don't really have to know.
I just found an inexpensive O2 sensor from this manufacturer - 2-wire, unheated for '97 Celica - for half of a Bosch. Ever hear of these guys?
No where in this post is the word "Replacement"!
Note that this is a universal fit O2 sensor, it has no wiring connector. Up to you, but I don't think anyone can give you an opinion on an O2 sensor that even the seller won't really say who manufactured it. Good luck if you choose to go this way.
You should make this a stickey in the general forums, that is very good trouble shooting advice, I am sure that these procedures would work on more than just Celicas.
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