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Old 09-13-2009, 02:11 PM   #1
grizzlyburr
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How tell a bad o2 sensor??

Hey guys I'm just curious to know how you can tell if your o2 sensor is bad.

Thanks a lot
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Old 09-13-2009, 03:00 PM   #2
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Re: how tell a bad o2 sensor??

1st clue would be a cell light. Like P1035 "o2 Sensor Heater Circuit Malfunction"
Sensor 2 is not important.
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Old 09-13-2009, 03:06 PM   #3
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Re: how tell a bad o2 sensor??

Well, you have two O2 sensors, and the best clue is if you get a check engine light. If you don't have a reader (I have a ScanGuage II mounted above my RR mirror that gives me all sorts of extra engine data, including the ability to read a CEL and also to clear them without disconnecting the battery), you've have to take the car somewhere to have the CEL read.

P0170- generally means front sensor (just below turbo) has gone bad. I had this CEL and replaced the front O2 sensor, it hasn't re-ocurred.

P0173- generally means rear sensor (after catalytic convertor) has gone bad.

Trouble codes on your car, go to 95 Eclipse (Turbo) 96-98 Vehicles OBD2: http://www.troublecodes.net/mitsu/

There are other trouble codes that show if your O2 sensor heater has crapped-out.
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132K daily driver. While I love the car, I sure see the difference between the build quality of my '97 DSM and the 6 and 9-year older Honda CRX's that I used to own. Things that almost never needed work on the Hondas fail at less than half the mileage driven (example- H/G replaced at 118K, my '88 CRX needed it done at 249K). No wonder Mitsubishi is all but out of business in the States, just hanging-on by their teeth w/ their current shitty product line-up (i-Miev, Mirage, & Outlander).
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Old 09-13-2009, 03:25 PM   #4
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Re: how tell a bad o2 sensor??

You can also physically check it by using these directions http://www.paladinmicro.com/PalMO2Sensors.htm
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Old 09-13-2009, 09:52 PM   #5
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Re: how tell a bad o2 sensor??

Okay that makes sense because i have a "service engine soon" light on. I'm also getting sub par gas mileage lol
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Old 09-14-2009, 01:11 AM   #6
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Re: how tell a bad o2 sensor??

Quote:
Originally Posted by grizzlyburr View Post
Okay that makes sense because i have a "service engine soon" light on. I'm also getting sub par gas mileage lol

Pull the trouble code and see what it says instead of ASSuming because I did that and replaced a good o2 just to find out the bad gas milaege was from a loose coolant sensor connection. In my case I even used Chilton's intructions to test the o2 but either chilton or I screwed up leading to believe the o2 was bad. Fyi I also replaced a good TPS sensor years ago with oem from local dealer for $105 after using chiltons instructions testing that one too so idk anymore about chilton. Now that was back before dsm forums, ebay, or easy access to the internet so don't get on my back for going to my local dealer for parts

Somebody mentioned oxygensensors.com and that's where I got mine for $50 and borrowed the tool from autozone to change it out which is an easy job. Just make sure you need one tho

Last edited by 91Bluebird; 09-14-2009 at 01:16 AM.
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Old 09-14-2009, 10:51 AM   #7
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Re: How tell a bad o2 sensor??

Most part stores like Advanced Auto and Checker will read your codes for free, most likely they'll tell you what the code means, as well.
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Old 09-14-2009, 11:32 AM   #8
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Re: How tell a bad o2 sensor??

Quote:
Originally Posted by 93_GSX View Post
Most part stores like Advanced Auto and Checker will read your codes for free, most likely they'll tell you what the code means, as well.

True but any self-respecting dsm'er would pull codes themselves and can do it in less time

If it is your oxygen sensor and you're tight on cash you can try cleaning the sensor 1st by letting it soak in ?gasoline? ??kerosene? (not sure which is best) because the holes on the sensor get clogged with carbon deposits. Also the car is quite old so you should check your connection at the o2 and make sure it's making good contact.
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Old 09-14-2009, 01:51 PM   #9
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Re: How tell a bad o2 sensor??

Alright I'll go to Checker and see if they can read it for me. If it does end up being the o2 sensor I'll try cleaning as suggested below.

Thanks for all the help,
Micah
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Old 04-08-2017, 11:38 PM   #10
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Re: How tell a bad o2 sensor??

I know this thread is old but it came up on a recent search while trying to find some info on the subject. I haven't found the info I need so i'll share my experience in the hopes it helps someone with similar problems. I have a Chilton but it doesn't give a pin diagram for the 2g turbo, only both 1g's as well as 2g non. It says on 2g turbo to use a specific test harness which costs more than the f'n o2 sensor.

I have a 98 GST Spyder. I recently got a CEL with a code of P0135 "o2 sensor heater circuit malfunction" This is the Denso 4 lead o2 sensor. Blue wire is dedicated output, white is ground, and 2 black wires are + and - for the heater. I don't trust that its a bad o2 sensor because I recently replaced my battery with a race battery and did some rewiring to the fuse box. My dilemma is that it might not be the o2 sensor, but actually no power to the o2 sensor heater. I got out my multimeter and checked for power on the connector from the fuse box. I'm getting 11.6 V from one of the connections where the black (heater) wires connects to, which would be the + heater wire. Next I tried to measure the resistance (Ohms) from the o2 sensor connector. I get no readings from any of the prongs on the connector. I ordered a new o2 sensor, will be installing it when it comes in and will give an update as to whether it fixes the problem.
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Old 04-16-2017, 09:21 PM   #11
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Re: How tell a bad o2 sensor??

I know it's been a week since you posted this, you may have figured it out already.
I always assumed the o2 sensor heater came from the ecu directly. do a google search on the ecu pinout for the appropriate car.
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Old 04-21-2017, 07:03 PM   #12
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Re: How tell a bad o2 sensor??

Well, I installed the new o2 sensor, and it seems to have fixed the problem. My CEL has not come back yet, but I haven't driven the car very much as this is not my daily driver. I'm going to clear a couple things up from my last post. The power to the heater is the only power that should be heading to the o2 sensor since it generates its own output signal when it is at normal operating temp, via the Blue dedicated out wire. Also I was checking resistance improperly from the o2 connector. I would need a wiring diagram to find the pin locations off of the ecu and connect the multi meter to the ecu harness pin and then the corresponding pin on the o2 connector. Anyways, hope this helps someone having problems. I'm off to put a test pipe on which will cause my CEL to come right back, but thats another story. Happy wrenching!
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Old 04-22-2017, 06:07 PM   #13
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Re: How tell a bad o2 sensor??

ECU Wiring:
1995:
http://imgur.com/a/RcaPi

1999:
http://imgur.com/a/7wyeh

As for the cat code, if you can't disable it through tuning, you can disable it mechanically for under $10. Go get a pack of spark plug non-foulers and space the rear o2 sensor out of the exhaust stream before re-installing the setup back into the exhaust pipe. You will need to "open up" one of the non-foulers in order for the o2 sensor to fully seat inside. It'll make sense once you get your hands on the non foulers.

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