That's what has me baffled, I replaced the upstream and it still says it's
the one that's either bad or something else is wrong. Could there be
something else wrong?

--On Thursday, July 28, 2005 12:09 PM -0700 J Strickland <spam@nospam.net>
wrote:

> In theory, it should. But the key trick came about with OBD I, which
> turns out to be a boondoggle from the perspective of consumers. OBD II
> is much better for the consumer because it provides uniforimity of
> design, which means that consumers can figure out what's wrong with the
> car, fix it, and reset the computer. The key trick still works with OBD
> II, but why struggle with it when you can use the diagnostic tool for
> free -- and this clears the code for you so you can be sure you are
> chasing a new malfunciton, or the same one you just got done working on.
>
> The Upstream Sensor is the one beween the motor and the CAT, the
> downstream sensor is after the CAT.
>
>
>
>
> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
> news:23501433.1122562493@dellme02.andrew.ad.cmu.ed u...
>> This is the weird part about my Jeep, I can and have done just that,
>> gone to the parts store and they hooked up the diagnostic tool and it
>> read O2 sensor upstream blah blah blah. I also can do the key trick. I
>> have two sensors, but if the other one at the cat went bad, wouldn't
>> the code read downstream?
>>
>> --On Thursday, July 28, 2005 10:42 AM -0700 J Strickland
>> <spam@nospam.net> wrote:
>>
>>> Your '96 is OBD II compliant, this means you can extract the codes
>>> quickly and easily with commercially available diagnostic equipment.
>>> Many auto parts stores will let you use the equipment free of charge on
>>> the assumption that the O2 Sensor(s) is(have) failed and you will come
>>> back in and buy them from the clerk on duty. The diagnostic tool will
>>> also reset the circuit and turn the Check light off.
>>>
>>>
>>>
>>>
>>>
>>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>>> news:1AD238B6DCDA4CE362DE47F3@boldme02.andrew.ad.c mu.edu...
>>>> I have a '96 GC Laredo with 158k, 4.0L. The check engine light came on
>>>> a couple of months ago and I did the 3 turns of the ignition switch and
>>>> the codes came up as 12,21,55. So, I figure it's time to replace the
>>>> O2 sensor, which I did. Now the check engine light comes on and then
>>>> goes out, it's the same codes. What could be the problem..........
>>>
>>>
>>
>>
>>
>>
>
>

 

I had the same thing happen. It said upstream, but after I replaced the one
at the cat, the light went off and stayed off. FWIW, napa, oreilly,
autozone, none of them had the correct sensor. I had to go to the
stealership to get the right sensor.
Dennis
97 Wrangler

"Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
news:2C2EEC53C4E97D3D8B05B428@boldme02.andrew.ad.c mu.edu...
> That's what has me baffled, I replaced the upstream and it still says it's
> the one that's either bad or something else is wrong. Could there be
> something else wrong?
>
> --On Thursday, July 28, 2005 12:09 PM -0700 J Strickland <spam@nospam.net>
> wrote:
>
>> In theory, it should. But the key trick came about with OBD I, which
>> turns out to be a boondoggle from the perspective of consumers. OBD II
>> is much better for the consumer because it provides uniforimity of
>> design, which means that consumers can figure out what's wrong with the
>> car, fix it, and reset the computer. The key trick still works with OBD
>> II, but why struggle with it when you can use the diagnostic tool for
>> free -- and this clears the code for you so you can be sure you are
>> chasing a new malfunciton, or the same one you just got done working on.
>>
>> The Upstream Sensor is the one beween the motor and the CAT, the
>> downstream sensor is after the CAT.
>>
>>
>>
>>
>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>> news:23501433.1122562493@dellme02.andrew.ad.cmu.ed u...
>>> This is the weird part about my Jeep, I can and have done just that,
>>> gone to the parts store and they hooked up the diagnostic tool and it
>>> read O2 sensor upstream blah blah blah. I also can do the key trick. I
>>> have two sensors, but if the other one at the cat went bad, wouldn't
>>> the code read downstream?
>>>
>>> --On Thursday, July 28, 2005 10:42 AM -0700 J Strickland
>>> <spam@nospam.net> wrote:
>>>
>>>> Your '96 is OBD II compliant, this means you can extract the codes
>>>> quickly and easily with commercially available diagnostic equipment.
>>>> Many auto parts stores will let you use the equipment free of charge
>>>> on
>>>> the assumption that the O2 Sensor(s) is(have) failed and you will come
>>>> back in and buy them from the clerk on duty. The diagnostic tool will
>>>> also reset the circuit and turn the Check light off.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>>>> news:1AD238B6DCDA4CE362DE47F3@boldme02.andrew.ad.c mu.edu...
>>>>> I have a '96 GC Laredo with 158k, 4.0L. The check engine light came on
>>>>> a couple of months ago and I did the 3 turns of the ignition switch
>>>>> and
>>>>> the codes came up as 12,21,55. So, I figure it's time to replace the
>>>>> O2 sensor, which I did. Now the check engine light comes on and then
>>>>> goes out, it's the same codes. What could be the problem..........
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>

 

I had the same thing happen. It said upstream, but after I replaced the one
at the cat, the light went off and stayed off. FWIW, napa, oreilly,
autozone, none of them had the correct sensor. I had to go to the
stealership to get the right sensor.
Dennis
97 Wrangler

"Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
news:2C2EEC53C4E97D3D8B05B428@boldme02.andrew.ad.c mu.edu...
> That's what has me baffled, I replaced the upstream and it still says it's
> the one that's either bad or something else is wrong. Could there be
> something else wrong?
>
> --On Thursday, July 28, 2005 12:09 PM -0700 J Strickland <spam@nospam.net>
> wrote:
>
>> In theory, it should. But the key trick came about with OBD I, which
>> turns out to be a boondoggle from the perspective of consumers. OBD II
>> is much better for the consumer because it provides uniforimity of
>> design, which means that consumers can figure out what's wrong with the
>> car, fix it, and reset the computer. The key trick still works with OBD
>> II, but why struggle with it when you can use the diagnostic tool for
>> free -- and this clears the code for you so you can be sure you are
>> chasing a new malfunciton, or the same one you just got done working on.
>>
>> The Upstream Sensor is the one beween the motor and the CAT, the
>> downstream sensor is after the CAT.
>>
>>
>>
>>
>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>> news:23501433.1122562493@dellme02.andrew.ad.cmu.ed u...
>>> This is the weird part about my Jeep, I can and have done just that,
>>> gone to the parts store and they hooked up the diagnostic tool and it
>>> read O2 sensor upstream blah blah blah. I also can do the key trick. I
>>> have two sensors, but if the other one at the cat went bad, wouldn't
>>> the code read downstream?
>>>
>>> --On Thursday, July 28, 2005 10:42 AM -0700 J Strickland
>>> <spam@nospam.net> wrote:
>>>
>>>> Your '96 is OBD II compliant, this means you can extract the codes
>>>> quickly and easily with commercially available diagnostic equipment.
>>>> Many auto parts stores will let you use the equipment free of charge
>>>> on
>>>> the assumption that the O2 Sensor(s) is(have) failed and you will come
>>>> back in and buy them from the clerk on duty. The diagnostic tool will
>>>> also reset the circuit and turn the Check light off.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>>>> news:1AD238B6DCDA4CE362DE47F3@boldme02.andrew.ad.c mu.edu...
>>>>> I have a '96 GC Laredo with 158k, 4.0L. The check engine light came on
>>>>> a couple of months ago and I did the 3 turns of the ignition switch
>>>>> and
>>>>> the codes came up as 12,21,55. So, I figure it's time to replace the
>>>>> O2 sensor, which I did. Now the check engine light comes on and then
>>>>> goes out, it's the same codes. What could be the problem..........
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>

 

I had the same thing happen. It said upstream, but after I replaced the one
at the cat, the light went off and stayed off. FWIW, napa, oreilly,
autozone, none of them had the correct sensor. I had to go to the
stealership to get the right sensor.
Dennis
97 Wrangler

"Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
news:2C2EEC53C4E97D3D8B05B428@boldme02.andrew.ad.c mu.edu...
> That's what has me baffled, I replaced the upstream and it still says it's
> the one that's either bad or something else is wrong. Could there be
> something else wrong?
>
> --On Thursday, July 28, 2005 12:09 PM -0700 J Strickland <spam@nospam.net>
> wrote:
>
>> In theory, it should. But the key trick came about with OBD I, which
>> turns out to be a boondoggle from the perspective of consumers. OBD II
>> is much better for the consumer because it provides uniforimity of
>> design, which means that consumers can figure out what's wrong with the
>> car, fix it, and reset the computer. The key trick still works with OBD
>> II, but why struggle with it when you can use the diagnostic tool for
>> free -- and this clears the code for you so you can be sure you are
>> chasing a new malfunciton, or the same one you just got done working on.
>>
>> The Upstream Sensor is the one beween the motor and the CAT, the
>> downstream sensor is after the CAT.
>>
>>
>>
>>
>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>> news:23501433.1122562493@dellme02.andrew.ad.cmu.ed u...
>>> This is the weird part about my Jeep, I can and have done just that,
>>> gone to the parts store and they hooked up the diagnostic tool and it
>>> read O2 sensor upstream blah blah blah. I also can do the key trick. I
>>> have two sensors, but if the other one at the cat went bad, wouldn't
>>> the code read downstream?
>>>
>>> --On Thursday, July 28, 2005 10:42 AM -0700 J Strickland
>>> <spam@nospam.net> wrote:
>>>
>>>> Your '96 is OBD II compliant, this means you can extract the codes
>>>> quickly and easily with commercially available diagnostic equipment.
>>>> Many auto parts stores will let you use the equipment free of charge
>>>> on
>>>> the assumption that the O2 Sensor(s) is(have) failed and you will come
>>>> back in and buy them from the clerk on duty. The diagnostic tool will
>>>> also reset the circuit and turn the Check light off.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>>>> news:1AD238B6DCDA4CE362DE47F3@boldme02.andrew.ad.c mu.edu...
>>>>> I have a '96 GC Laredo with 158k, 4.0L. The check engine light came on
>>>>> a couple of months ago and I did the 3 turns of the ignition switch
>>>>> and
>>>>> the codes came up as 12,21,55. So, I figure it's time to replace the
>>>>> O2 sensor, which I did. Now the check engine light comes on and then
>>>>> goes out, it's the same codes. What could be the problem..........
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>

 

I had the same thing happen. It said upstream, but after I replaced the one
at the cat, the light went off and stayed off. FWIW, napa, oreilly,
autozone, none of them had the correct sensor. I had to go to the
stealership to get the right sensor.
Dennis
97 Wrangler

"Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
news:2C2EEC53C4E97D3D8B05B428@boldme02.andrew.ad.c mu.edu...
> That's what has me baffled, I replaced the upstream and it still says it's
> the one that's either bad or something else is wrong. Could there be
> something else wrong?
>
> --On Thursday, July 28, 2005 12:09 PM -0700 J Strickland <spam@nospam.net>
> wrote:
>
>> In theory, it should. But the key trick came about with OBD I, which
>> turns out to be a boondoggle from the perspective of consumers. OBD II
>> is much better for the consumer because it provides uniforimity of
>> design, which means that consumers can figure out what's wrong with the
>> car, fix it, and reset the computer. The key trick still works with OBD
>> II, but why struggle with it when you can use the diagnostic tool for
>> free -- and this clears the code for you so you can be sure you are
>> chasing a new malfunciton, or the same one you just got done working on.
>>
>> The Upstream Sensor is the one beween the motor and the CAT, the
>> downstream sensor is after the CAT.
>>
>>
>>
>>
>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>> news:23501433.1122562493@dellme02.andrew.ad.cmu.ed u...
>>> This is the weird part about my Jeep, I can and have done just that,
>>> gone to the parts store and they hooked up the diagnostic tool and it
>>> read O2 sensor upstream blah blah blah. I also can do the key trick. I
>>> have two sensors, but if the other one at the cat went bad, wouldn't
>>> the code read downstream?
>>>
>>> --On Thursday, July 28, 2005 10:42 AM -0700 J Strickland
>>> <spam@nospam.net> wrote:
>>>
>>>> Your '96 is OBD II compliant, this means you can extract the codes
>>>> quickly and easily with commercially available diagnostic equipment.
>>>> Many auto parts stores will let you use the equipment free of charge
>>>> on
>>>> the assumption that the O2 Sensor(s) is(have) failed and you will come
>>>> back in and buy them from the clerk on duty. The diagnostic tool will
>>>> also reset the circuit and turn the Check light off.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>>>> news:1AD238B6DCDA4CE362DE47F3@boldme02.andrew.ad.c mu.edu...
>>>>> I have a '96 GC Laredo with 158k, 4.0L. The check engine light came on
>>>>> a couple of months ago and I did the 3 turns of the ignition switch
>>>>> and
>>>>> the codes came up as 12,21,55. So, I figure it's time to replace the
>>>>> O2 sensor, which I did. Now the check engine light comes on and then
>>>>> goes out, it's the same codes. What could be the problem..........
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>

 

I'm not sure that the code gets reset automatically when you fix the errant
part, or if you have to physically reset the code yourself. I think the
latter is the case though. This means you will still get the old code even
with the new part. Of course, there is always the possibility that the part
or the connection is somehow faulty.




"Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
news:2C2EEC53C4E97D3D8B05B428@boldme02.andrew.ad.c mu.edu...
> That's what has me baffled, I replaced the upstream and it still says it's
> the one that's either bad or something else is wrong. Could there be
> something else wrong?
>
> --On Thursday, July 28, 2005 12:09 PM -0700 J Strickland <spam@nospam.net>
> wrote:
>
>> In theory, it should. But the key trick came about with OBD I, which
>> turns out to be a boondoggle from the perspective of consumers. OBD II
>> is much better for the consumer because it provides uniforimity of
>> design, which means that consumers can figure out what's wrong with the
>> car, fix it, and reset the computer. The key trick still works with OBD
>> II, but why struggle with it when you can use the diagnostic tool for
>> free -- and this clears the code for you so you can be sure you are
>> chasing a new malfunciton, or the same one you just got done working on.
>>
>> The Upstream Sensor is the one beween the motor and the CAT, the
>> downstream sensor is after the CAT.
>>
>>
>>
>>
>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>> news:23501433.1122562493@dellme02.andrew.ad.cmu.ed u...
>>> This is the weird part about my Jeep, I can and have done just that,
>>> gone to the parts store and they hooked up the diagnostic tool and it
>>> read O2 sensor upstream blah blah blah. I also can do the key trick. I
>>> have two sensors, but if the other one at the cat went bad, wouldn't
>>> the code read downstream?
>>>
>>> --On Thursday, July 28, 2005 10:42 AM -0700 J Strickland
>>> <spam@nospam.net> wrote:
>>>
>>>> Your '96 is OBD II compliant, this means you can extract the codes
>>>> quickly and easily with commercially available diagnostic equipment.
>>>> Many auto parts stores will let you use the equipment free of charge
>>>> on
>>>> the assumption that the O2 Sensor(s) is(have) failed and you will come
>>>> back in and buy them from the clerk on duty. The diagnostic tool will
>>>> also reset the circuit and turn the Check light off.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>>>> news:1AD238B6DCDA4CE362DE47F3@boldme02.andrew.ad.c mu.edu...
>>>>> I have a '96 GC Laredo with 158k, 4.0L. The check engine light came on
>>>>> a couple of months ago and I did the 3 turns of the ignition switch
>>>>> and
>>>>> the codes came up as 12,21,55. So, I figure it's time to replace the
>>>>> O2 sensor, which I did. Now the check engine light comes on and then
>>>>> goes out, it's the same codes. What could be the problem..........
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>

 

I'm not sure that the code gets reset automatically when you fix the errant
part, or if you have to physically reset the code yourself. I think the
latter is the case though. This means you will still get the old code even
with the new part. Of course, there is always the possibility that the part
or the connection is somehow faulty.




"Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
news:2C2EEC53C4E97D3D8B05B428@boldme02.andrew.ad.c mu.edu...
> That's what has me baffled, I replaced the upstream and it still says it's
> the one that's either bad or something else is wrong. Could there be
> something else wrong?
>
> --On Thursday, July 28, 2005 12:09 PM -0700 J Strickland <spam@nospam.net>
> wrote:
>
>> In theory, it should. But the key trick came about with OBD I, which
>> turns out to be a boondoggle from the perspective of consumers. OBD II
>> is much better for the consumer because it provides uniforimity of
>> design, which means that consumers can figure out what's wrong with the
>> car, fix it, and reset the computer. The key trick still works with OBD
>> II, but why struggle with it when you can use the diagnostic tool for
>> free -- and this clears the code for you so you can be sure you are
>> chasing a new malfunciton, or the same one you just got done working on.
>>
>> The Upstream Sensor is the one beween the motor and the CAT, the
>> downstream sensor is after the CAT.
>>
>>
>>
>>
>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>> news:23501433.1122562493@dellme02.andrew.ad.cmu.ed u...
>>> This is the weird part about my Jeep, I can and have done just that,
>>> gone to the parts store and they hooked up the diagnostic tool and it
>>> read O2 sensor upstream blah blah blah. I also can do the key trick. I
>>> have two sensors, but if the other one at the cat went bad, wouldn't
>>> the code read downstream?
>>>
>>> --On Thursday, July 28, 2005 10:42 AM -0700 J Strickland
>>> <spam@nospam.net> wrote:
>>>
>>>> Your '96 is OBD II compliant, this means you can extract the codes
>>>> quickly and easily with commercially available diagnostic equipment.
>>>> Many auto parts stores will let you use the equipment free of charge
>>>> on
>>>> the assumption that the O2 Sensor(s) is(have) failed and you will come
>>>> back in and buy them from the clerk on duty. The diagnostic tool will
>>>> also reset the circuit and turn the Check light off.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>>>> news:1AD238B6DCDA4CE362DE47F3@boldme02.andrew.ad.c mu.edu...
>>>>> I have a '96 GC Laredo with 158k, 4.0L. The check engine light came on
>>>>> a couple of months ago and I did the 3 turns of the ignition switch
>>>>> and
>>>>> the codes came up as 12,21,55. So, I figure it's time to replace the
>>>>> O2 sensor, which I did. Now the check engine light comes on and then
>>>>> goes out, it's the same codes. What could be the problem..........
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>

 

I'm not sure that the code gets reset automatically when you fix the errant
part, or if you have to physically reset the code yourself. I think the
latter is the case though. This means you will still get the old code even
with the new part. Of course, there is always the possibility that the part
or the connection is somehow faulty.




"Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
news:2C2EEC53C4E97D3D8B05B428@boldme02.andrew.ad.c mu.edu...
> That's what has me baffled, I replaced the upstream and it still says it's
> the one that's either bad or something else is wrong. Could there be
> something else wrong?
>
> --On Thursday, July 28, 2005 12:09 PM -0700 J Strickland <spam@nospam.net>
> wrote:
>
>> In theory, it should. But the key trick came about with OBD I, which
>> turns out to be a boondoggle from the perspective of consumers. OBD II
>> is much better for the consumer because it provides uniforimity of
>> design, which means that consumers can figure out what's wrong with the
>> car, fix it, and reset the computer. The key trick still works with OBD
>> II, but why struggle with it when you can use the diagnostic tool for
>> free -- and this clears the code for you so you can be sure you are
>> chasing a new malfunciton, or the same one you just got done working on.
>>
>> The Upstream Sensor is the one beween the motor and the CAT, the
>> downstream sensor is after the CAT.
>>
>>
>>
>>
>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>> news:23501433.1122562493@dellme02.andrew.ad.cmu.ed u...
>>> This is the weird part about my Jeep, I can and have done just that,
>>> gone to the parts store and they hooked up the diagnostic tool and it
>>> read O2 sensor upstream blah blah blah. I also can do the key trick. I
>>> have two sensors, but if the other one at the cat went bad, wouldn't
>>> the code read downstream?
>>>
>>> --On Thursday, July 28, 2005 10:42 AM -0700 J Strickland
>>> <spam@nospam.net> wrote:
>>>
>>>> Your '96 is OBD II compliant, this means you can extract the codes
>>>> quickly and easily with commercially available diagnostic equipment.
>>>> Many auto parts stores will let you use the equipment free of charge
>>>> on
>>>> the assumption that the O2 Sensor(s) is(have) failed and you will come
>>>> back in and buy them from the clerk on duty. The diagnostic tool will
>>>> also reset the circuit and turn the Check light off.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>>>> news:1AD238B6DCDA4CE362DE47F3@boldme02.andrew.ad.c mu.edu...
>>>>> I have a '96 GC Laredo with 158k, 4.0L. The check engine light came on
>>>>> a couple of months ago and I did the 3 turns of the ignition switch
>>>>> and
>>>>> the codes came up as 12,21,55. So, I figure it's time to replace the
>>>>> O2 sensor, which I did. Now the check engine light comes on and then
>>>>> goes out, it's the same codes. What could be the problem..........
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>

 

I'm not sure that the code gets reset automatically when you fix the errant
part, or if you have to physically reset the code yourself. I think the
latter is the case though. This means you will still get the old code even
with the new part. Of course, there is always the possibility that the part
or the connection is somehow faulty.




"Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
news:2C2EEC53C4E97D3D8B05B428@boldme02.andrew.ad.c mu.edu...
> That's what has me baffled, I replaced the upstream and it still says it's
> the one that's either bad or something else is wrong. Could there be
> something else wrong?
>
> --On Thursday, July 28, 2005 12:09 PM -0700 J Strickland <spam@nospam.net>
> wrote:
>
>> In theory, it should. But the key trick came about with OBD I, which
>> turns out to be a boondoggle from the perspective of consumers. OBD II
>> is much better for the consumer because it provides uniforimity of
>> design, which means that consumers can figure out what's wrong with the
>> car, fix it, and reset the computer. The key trick still works with OBD
>> II, but why struggle with it when you can use the diagnostic tool for
>> free -- and this clears the code for you so you can be sure you are
>> chasing a new malfunciton, or the same one you just got done working on.
>>
>> The Upstream Sensor is the one beween the motor and the CAT, the
>> downstream sensor is after the CAT.
>>
>>
>>
>>
>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>> news:23501433.1122562493@dellme02.andrew.ad.cmu.ed u...
>>> This is the weird part about my Jeep, I can and have done just that,
>>> gone to the parts store and they hooked up the diagnostic tool and it
>>> read O2 sensor upstream blah blah blah. I also can do the key trick. I
>>> have two sensors, but if the other one at the cat went bad, wouldn't
>>> the code read downstream?
>>>
>>> --On Thursday, July 28, 2005 10:42 AM -0700 J Strickland
>>> <spam@nospam.net> wrote:
>>>
>>>> Your '96 is OBD II compliant, this means you can extract the codes
>>>> quickly and easily with commercially available diagnostic equipment.
>>>> Many auto parts stores will let you use the equipment free of charge
>>>> on
>>>> the assumption that the O2 Sensor(s) is(have) failed and you will come
>>>> back in and buy them from the clerk on duty. The diagnostic tool will
>>>> also reset the circuit and turn the Check light off.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> "Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
>>>> news:1AD238B6DCDA4CE362DE47F3@boldme02.andrew.ad.c mu.edu...
>>>>> I have a '96 GC Laredo with 158k, 4.0L. The check engine light came on
>>>>> a couple of months ago and I did the 3 turns of the ignition switch
>>>>> and
>>>>> the codes came up as 12,21,55. So, I figure it's time to replace the
>>>>> O2 sensor, which I did. Now the check engine light comes on and then
>>>>> goes out, it's the same codes. What could be the problem..........
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>
>

 

Check your exhaust manifold for cracks.

Troy


"Ed Wojciechowski" <wojo@andrew.cmu.edu> wrote in message
news:1AD238B6DCDA4CE362DE47F3@boldme02.andrew.ad.c mu.edu...
> I have a '96 GC Laredo with 158k, 4.0L. The check engine light came on a
> couple of months ago and I did the 3 turns of the ignition switch and the
> codes came up as 12,21,55. So, I figure it's time to replace the O2
sensor,
> which I did. Now the check engine light comes on and then goes out, it's
> the same codes. What could be the problem..........