Re: check engine light on in 97 wrangler YJ with error code reading 72
 

On Thu, 18 Jan 2007 18:41:15 GMT, "Jeff Strickland"
<crwlr@verizon.net> wrote:

>
>"DougW" <post.replies@invalid.address> wrote in message
>news:d8drh.41182$oA1.30083@newsfe19.lga...
>> Jeff Strickland wrote:
>>> "bllsht" wrote ...
>>>> "DougW" wrote:
>>>>
>>>>> bspear78 wrote:
>>>>>> I have a check engine light on, and the code is reading a 12 and a
>>>>>> 72. I know what the 12 means, but could not find any explanation
>>>>>> for a reading of 72. Anyone know what this means?
>>>>>
>>>>> 72 Catalyst efficiency below required level. (Same as code 64)
>>>>>
>>>>> This means one of two things.
>>>>> 1) your catalytic converter is plugging/cracking/failing
>>>>> 2) the O2 sensor behind the cat is failing
>>>>
>>>> If the downstream O2 was failing you'd get a downstream O2 fault, not
>>>> a cat efficiency fault.
>>>>
>>>
>>> I'm not sure that is true in an OBD I car. The CAT is not a likely
>>> source of problems, and my money is on the after-CAT sensor going bad.
>>>
>>> I am pretty sure that the downstream sensor can give an error that
>>> says the CAT is failing. This can happen because the system doesn't
>>> know that the sensor is bad, it only knows that the input from the
>>> sensor is not correct. The sensor can fail in a mode that makes the
>>> system say that the CAT is not working when the reality is that the
>>> sensor itself has taken a bye.
>>> Having said all of that, the OP says he has a 97 YJ. In the 97, it was
>>> called a TJ, and in 97, the codes are OBD II.
>>
>> I've seen O2 sensors go bad, but not bad enough to set a fault. Usually
>> it's the forward one and the only thing it does is give you bad milage
>> and black exhaust. Figured the rearward one could go equally bad and
>> throw a code even if the cat was good.
>>
>
>
>I agree, usually it's the front sensor. But, the CAT's condition is not
>checked at the front, it's checked at the back.
>
>The "front" (upstream) sensor will adjust the fuel mix as much as it can,
>and eventually throw a code that results from detecting an out of range
>condition (rich or lean mixture) that the computer is not able to adjust
>fuel delivery to correct for. The out of range can be true or false. If
>true, the cause can be related to stuff associated with fuel delivery --
>faulty injectors, that sort of thing -- but if false, then the trouble is a
>faulty sensor.
>
>The "back" (downstream) sensor is looking at what comes out of the CAT. It
>can also give a true or false report. If the report is true, the cause is a
>faulty CAT, but if false, the cause is a faulty sensor. Given the
>environment (hot exhaust stream), I tend to look at faulty sensors,
>especially when the CAT is reported as the trouble. The CAT itself is very
>robust, and is capable of lasting nearly as long as the vehicle it is
>mounted to. The sensor is not so robust.
>
>If the code says that the CAT is below efficiency, I'd be thinking the
>sensor that reports the CAT is what is really below efficiency. If the
>problem was happening at the upstream sensor, the report would not be that
>the CAT is bad, because such data would be collected before the CAT comes
>into play. A report from the upstream sensor would include information that
>the fuel mixture was 1.) too rich, 2.) too lean, or 3.) out of range,
>without an indication as to the content of the mixture. The downstream
>sensor does not know about to rich or too lean, it only knows that what
>comes out of the CAT has not been cleaned up, relative to what went in. The
>upstream sensor knows what goes into the CAT, the downstream sensor knows
>what comes out.
>
>
>



You're both leaping to conclusions without even having a clue as to
how the PCM determines the cat converter's efficiency.

Re: check engine light on in 97 wrangler YJ with error code reading 72
 

On Thu, 18 Jan 2007 18:41:15 GMT, "Jeff Strickland"
<crwlr@verizon.net> wrote:

>
>"DougW" <post.replies@invalid.address> wrote in message
>news:d8drh.41182$oA1.30083@newsfe19.lga...
>> Jeff Strickland wrote:
>>> "bllsht" wrote ...
>>>> "DougW" wrote:
>>>>
>>>>> bspear78 wrote:
>>>>>> I have a check engine light on, and the code is reading a 12 and a
>>>>>> 72. I know what the 12 means, but could not find any explanation
>>>>>> for a reading of 72. Anyone know what this means?
>>>>>
>>>>> 72 Catalyst efficiency below required level. (Same as code 64)
>>>>>
>>>>> This means one of two things.
>>>>> 1) your catalytic converter is plugging/cracking/failing
>>>>> 2) the O2 sensor behind the cat is failing
>>>>
>>>> If the downstream O2 was failing you'd get a downstream O2 fault, not
>>>> a cat efficiency fault.
>>>>
>>>
>>> I'm not sure that is true in an OBD I car. The CAT is not a likely
>>> source of problems, and my money is on the after-CAT sensor going bad.
>>>
>>> I am pretty sure that the downstream sensor can give an error that
>>> says the CAT is failing. This can happen because the system doesn't
>>> know that the sensor is bad, it only knows that the input from the
>>> sensor is not correct. The sensor can fail in a mode that makes the
>>> system say that the CAT is not working when the reality is that the
>>> sensor itself has taken a bye.
>>> Having said all of that, the OP says he has a 97 YJ. In the 97, it was
>>> called a TJ, and in 97, the codes are OBD II.
>>
>> I've seen O2 sensors go bad, but not bad enough to set a fault. Usually
>> it's the forward one and the only thing it does is give you bad milage
>> and black exhaust. Figured the rearward one could go equally bad and
>> throw a code even if the cat was good.
>>
>
>
>I agree, usually it's the front sensor. But, the CAT's condition is not
>checked at the front, it's checked at the back.
>
>The "front" (upstream) sensor will adjust the fuel mix as much as it can,
>and eventually throw a code that results from detecting an out of range
>condition (rich or lean mixture) that the computer is not able to adjust
>fuel delivery to correct for. The out of range can be true or false. If
>true, the cause can be related to stuff associated with fuel delivery --
>faulty injectors, that sort of thing -- but if false, then the trouble is a
>faulty sensor.
>
>The "back" (downstream) sensor is looking at what comes out of the CAT. It
>can also give a true or false report. If the report is true, the cause is a
>faulty CAT, but if false, the cause is a faulty sensor. Given the
>environment (hot exhaust stream), I tend to look at faulty sensors,
>especially when the CAT is reported as the trouble. The CAT itself is very
>robust, and is capable of lasting nearly as long as the vehicle it is
>mounted to. The sensor is not so robust.
>
>If the code says that the CAT is below efficiency, I'd be thinking the
>sensor that reports the CAT is what is really below efficiency. If the
>problem was happening at the upstream sensor, the report would not be that
>the CAT is bad, because such data would be collected before the CAT comes
>into play. A report from the upstream sensor would include information that
>the fuel mixture was 1.) too rich, 2.) too lean, or 3.) out of range,
>without an indication as to the content of the mixture. The downstream
>sensor does not know about to rich or too lean, it only knows that what
>comes out of the CAT has not been cleaned up, relative to what went in. The
>upstream sensor knows what goes into the CAT, the downstream sensor knows
>what comes out.
>
>
>



You're both leaping to conclusions without even having a clue as to
how the PCM determines the cat converter's efficiency.

Re: check engine light on in 97 wrangler YJ with error code reading 72
 

On Thu, 18 Jan 2007 18:41:15 GMT, "Jeff Strickland"
<crwlr@verizon.net> wrote:

>
>"DougW" <post.replies@invalid.address> wrote in message
>news:d8drh.41182$oA1.30083@newsfe19.lga...
>> Jeff Strickland wrote:
>>> "bllsht" wrote ...
>>>> "DougW" wrote:
>>>>
>>>>> bspear78 wrote:
>>>>>> I have a check engine light on, and the code is reading a 12 and a
>>>>>> 72. I know what the 12 means, but could not find any explanation
>>>>>> for a reading of 72. Anyone know what this means?
>>>>>
>>>>> 72 Catalyst efficiency below required level. (Same as code 64)
>>>>>
>>>>> This means one of two things.
>>>>> 1) your catalytic converter is plugging/cracking/failing
>>>>> 2) the O2 sensor behind the cat is failing
>>>>
>>>> If the downstream O2 was failing you'd get a downstream O2 fault, not
>>>> a cat efficiency fault.
>>>>
>>>
>>> I'm not sure that is true in an OBD I car. The CAT is not a likely
>>> source of problems, and my money is on the after-CAT sensor going bad.
>>>
>>> I am pretty sure that the downstream sensor can give an error that
>>> says the CAT is failing. This can happen because the system doesn't
>>> know that the sensor is bad, it only knows that the input from the
>>> sensor is not correct. The sensor can fail in a mode that makes the
>>> system say that the CAT is not working when the reality is that the
>>> sensor itself has taken a bye.
>>> Having said all of that, the OP says he has a 97 YJ. In the 97, it was
>>> called a TJ, and in 97, the codes are OBD II.
>>
>> I've seen O2 sensors go bad, but not bad enough to set a fault. Usually
>> it's the forward one and the only thing it does is give you bad milage
>> and black exhaust. Figured the rearward one could go equally bad and
>> throw a code even if the cat was good.
>>
>
>
>I agree, usually it's the front sensor. But, the CAT's condition is not
>checked at the front, it's checked at the back.
>
>The "front" (upstream) sensor will adjust the fuel mix as much as it can,
>and eventually throw a code that results from detecting an out of range
>condition (rich or lean mixture) that the computer is not able to adjust
>fuel delivery to correct for. The out of range can be true or false. If
>true, the cause can be related to stuff associated with fuel delivery --
>faulty injectors, that sort of thing -- but if false, then the trouble is a
>faulty sensor.
>
>The "back" (downstream) sensor is looking at what comes out of the CAT. It
>can also give a true or false report. If the report is true, the cause is a
>faulty CAT, but if false, the cause is a faulty sensor. Given the
>environment (hot exhaust stream), I tend to look at faulty sensors,
>especially when the CAT is reported as the trouble. The CAT itself is very
>robust, and is capable of lasting nearly as long as the vehicle it is
>mounted to. The sensor is not so robust.
>
>If the code says that the CAT is below efficiency, I'd be thinking the
>sensor that reports the CAT is what is really below efficiency. If the
>problem was happening at the upstream sensor, the report would not be that
>the CAT is bad, because such data would be collected before the CAT comes
>into play. A report from the upstream sensor would include information that
>the fuel mixture was 1.) too rich, 2.) too lean, or 3.) out of range,
>without an indication as to the content of the mixture. The downstream
>sensor does not know about to rich or too lean, it only knows that what
>comes out of the CAT has not been cleaned up, relative to what went in. The
>upstream sensor knows what goes into the CAT, the downstream sensor knows
>what comes out.
>
>
>



You're both leaping to conclusions without even having a clue as to
how the PCM determines the cat converter's efficiency.

Re: check engine light on in 97 wrangler YJ with error code reading 72
 

"bllsht" <nospam@dot.net> wrote in message
news:l9i0r25jnn68gvl1b940fdlkuelml6jh4f@4ax.com...
> On Thu, 18 Jan 2007 19:01:19 GMT, "Jeff Strickland"
> <crwlr@verizon.net> wrote:
>
>>
>>"bllsht" <nospam@dot.net> wrote in message
>>news:nigrq2h2vlm58ducoftq5of5rvi6khcsp9@4ax.com. ..
>>> On Tue, 16 Jan 2007 20:03:42 GMT, "Jeff Strickland"
>>> <crwlr@verizon.net> wrote:
>>>
>>>>
>>>>"bllsht" <nospam@dot.net> wrote in message
>>>>news:567mq2lcmmf2td23fj2mo0bsfndgffg805@4ax.co m...
>>>>> On Sun, 14 Jan 2007 14:41:18 -0600, "DougW"
>>>>> <post.replies@invalid.address> wrote:
>>>>>
>>>>>>bspear78 wrote:
>>>>>>> I have a check engine light on, and the code is reading a 12 and a
>>>>>>> 72.
>>>>>>> I know what the 12 means, but could not find any explanation for a
>>>>>>> reading of 72. Anyone know what this means?
>>>>>>
>>>>>>72 Catalyst efficiency below required level. (Same as code 64)
>>>>>>
>>>>>>This means one of two things.
>>>>>>1) your catalytic converter is plugging/cracking/failing
>>>>>>2) the O2 sensor behind the cat is failing
>>>>>
>>>>> If the downstream O2 was failing you'd get a downstream O2 fault, not
>>>>> a cat efficiency fault.
>>>>>
>>>>
>>>>I'm not sure that is true in an OBD I car. The CAT is not a likely
>>>>source
>>>>of
>>>>problems, and my money is on the after-CAT sensor going bad.
>>>
>>> An OBD I jeep wouldn't even have a downstream O2 sensor. You just lost
>>> your money.
>>>
>>>>
>>>>I am pretty sure that the downstream sensor can give an error that says
>>>>the
>>>>CAT is failing. This can happen because the system doesn't know that the
>>>>sensor is bad, it only knows that the input from the sensor is not
>>>>correct.
>>>>The sensor can fail in a mode that makes the system say that the CAT is
>>>>not
>>>>working when the reality is that the sensor itself has taken a bye.
>>>
>>> Wrong. A failed downstream sensor will not set a cat efficiency fault.
>>> In fact, the poorer the downstream sensor functions, the less likely a
>>> cat fault would result.
>>>
>>>>
>>>>Having said all of that, the OP says he has a 97 YJ. In the 97, it was
>>>>called a TJ, and in 97, the codes are OBD II.
>>>
>>> A 1997 vehicle would be OBD II, no matter what it was called, or who
>>> made it.
>>>
>>
>>Well, then we're all chasing our shadows. Because, an OBD II car won't
>>have
>>a Code 72 ...
>
> Oh really? Please tell us how you came to that conclusion.
>

Which conclusion?

OBD II specs say that the code will be something like P0440, where there is
an alpha digit followed by 4 numeric digits. 72 does not fit the spec.

Would you like the link to the OBD II spec?

Re: check engine light on in 97 wrangler YJ with error code reading 72
 

"bllsht" <nospam@dot.net> wrote in message
news:l9i0r25jnn68gvl1b940fdlkuelml6jh4f@4ax.com...
> On Thu, 18 Jan 2007 19:01:19 GMT, "Jeff Strickland"
> <crwlr@verizon.net> wrote:
>
>>
>>"bllsht" <nospam@dot.net> wrote in message
>>news:nigrq2h2vlm58ducoftq5of5rvi6khcsp9@4ax.com. ..
>>> On Tue, 16 Jan 2007 20:03:42 GMT, "Jeff Strickland"
>>> <crwlr@verizon.net> wrote:
>>>
>>>>
>>>>"bllsht" <nospam@dot.net> wrote in message
>>>>news:567mq2lcmmf2td23fj2mo0bsfndgffg805@4ax.co m...
>>>>> On Sun, 14 Jan 2007 14:41:18 -0600, "DougW"
>>>>> <post.replies@invalid.address> wrote:
>>>>>
>>>>>>bspear78 wrote:
>>>>>>> I have a check engine light on, and the code is reading a 12 and a
>>>>>>> 72.
>>>>>>> I know what the 12 means, but could not find any explanation for a
>>>>>>> reading of 72. Anyone know what this means?
>>>>>>
>>>>>>72 Catalyst efficiency below required level. (Same as code 64)
>>>>>>
>>>>>>This means one of two things.
>>>>>>1) your catalytic converter is plugging/cracking/failing
>>>>>>2) the O2 sensor behind the cat is failing
>>>>>
>>>>> If the downstream O2 was failing you'd get a downstream O2 fault, not
>>>>> a cat efficiency fault.
>>>>>
>>>>
>>>>I'm not sure that is true in an OBD I car. The CAT is not a likely
>>>>source
>>>>of
>>>>problems, and my money is on the after-CAT sensor going bad.
>>>
>>> An OBD I jeep wouldn't even have a downstream O2 sensor. You just lost
>>> your money.
>>>
>>>>
>>>>I am pretty sure that the downstream sensor can give an error that says
>>>>the
>>>>CAT is failing. This can happen because the system doesn't know that the
>>>>sensor is bad, it only knows that the input from the sensor is not
>>>>correct.
>>>>The sensor can fail in a mode that makes the system say that the CAT is
>>>>not
>>>>working when the reality is that the sensor itself has taken a bye.
>>>
>>> Wrong. A failed downstream sensor will not set a cat efficiency fault.
>>> In fact, the poorer the downstream sensor functions, the less likely a
>>> cat fault would result.
>>>
>>>>
>>>>Having said all of that, the OP says he has a 97 YJ. In the 97, it was
>>>>called a TJ, and in 97, the codes are OBD II.
>>>
>>> A 1997 vehicle would be OBD II, no matter what it was called, or who
>>> made it.
>>>
>>
>>Well, then we're all chasing our shadows. Because, an OBD II car won't
>>have
>>a Code 72 ...
>
> Oh really? Please tell us how you came to that conclusion.
>

Which conclusion?

OBD II specs say that the code will be something like P0440, where there is
an alpha digit followed by 4 numeric digits. 72 does not fit the spec.

Would you like the link to the OBD II spec?

Re: check engine light on in 97 wrangler YJ with error code reading 72
 

"bllsht" <nospam@dot.net> wrote in message
news:l9i0r25jnn68gvl1b940fdlkuelml6jh4f@4ax.com...
> On Thu, 18 Jan 2007 19:01:19 GMT, "Jeff Strickland"
> <crwlr@verizon.net> wrote:
>
>>
>>"bllsht" <nospam@dot.net> wrote in message
>>news:nigrq2h2vlm58ducoftq5of5rvi6khcsp9@4ax.com. ..
>>> On Tue, 16 Jan 2007 20:03:42 GMT, "Jeff Strickland"
>>> <crwlr@verizon.net> wrote:
>>>
>>>>
>>>>"bllsht" <nospam@dot.net> wrote in message
>>>>news:567mq2lcmmf2td23fj2mo0bsfndgffg805@4ax.co m...
>>>>> On Sun, 14 Jan 2007 14:41:18 -0600, "DougW"
>>>>> <post.replies@invalid.address> wrote:
>>>>>
>>>>>>bspear78 wrote:
>>>>>>> I have a check engine light on, and the code is reading a 12 and a
>>>>>>> 72.
>>>>>>> I know what the 12 means, but could not find any explanation for a
>>>>>>> reading of 72. Anyone know what this means?
>>>>>>
>>>>>>72 Catalyst efficiency below required level. (Same as code 64)
>>>>>>
>>>>>>This means one of two things.
>>>>>>1) your catalytic converter is plugging/cracking/failing
>>>>>>2) the O2 sensor behind the cat is failing
>>>>>
>>>>> If the downstream O2 was failing you'd get a downstream O2 fault, not
>>>>> a cat efficiency fault.
>>>>>
>>>>
>>>>I'm not sure that is true in an OBD I car. The CAT is not a likely
>>>>source
>>>>of
>>>>problems, and my money is on the after-CAT sensor going bad.
>>>
>>> An OBD I jeep wouldn't even have a downstream O2 sensor. You just lost
>>> your money.
>>>
>>>>
>>>>I am pretty sure that the downstream sensor can give an error that says
>>>>the
>>>>CAT is failing. This can happen because the system doesn't know that the
>>>>sensor is bad, it only knows that the input from the sensor is not
>>>>correct.
>>>>The sensor can fail in a mode that makes the system say that the CAT is
>>>>not
>>>>working when the reality is that the sensor itself has taken a bye.
>>>
>>> Wrong. A failed downstream sensor will not set a cat efficiency fault.
>>> In fact, the poorer the downstream sensor functions, the less likely a
>>> cat fault would result.
>>>
>>>>
>>>>Having said all of that, the OP says he has a 97 YJ. In the 97, it was
>>>>called a TJ, and in 97, the codes are OBD II.
>>>
>>> A 1997 vehicle would be OBD II, no matter what it was called, or who
>>> made it.
>>>
>>
>>Well, then we're all chasing our shadows. Because, an OBD II car won't
>>have
>>a Code 72 ...
>
> Oh really? Please tell us how you came to that conclusion.
>

Which conclusion?

OBD II specs say that the code will be something like P0440, where there is
an alpha digit followed by 4 numeric digits. 72 does not fit the spec.

Would you like the link to the OBD II spec?

Re: check engine light on in 97 wrangler YJ with error code reading 72
 

"bllsht" <nospam@dot.net> wrote in message
news:l9i0r25jnn68gvl1b940fdlkuelml6jh4f@4ax.com...
> On Thu, 18 Jan 2007 19:01:19 GMT, "Jeff Strickland"
> <crwlr@verizon.net> wrote:
>
>>
>>"bllsht" <nospam@dot.net> wrote in message
>>news:nigrq2h2vlm58ducoftq5of5rvi6khcsp9@4ax.com. ..
>>> On Tue, 16 Jan 2007 20:03:42 GMT, "Jeff Strickland"
>>> <crwlr@verizon.net> wrote:
>>>
>>>>
>>>>"bllsht" <nospam@dot.net> wrote in message
>>>>news:567mq2lcmmf2td23fj2mo0bsfndgffg805@4ax.co m...
>>>>> On Sun, 14 Jan 2007 14:41:18 -0600, "DougW"
>>>>> <post.replies@invalid.address> wrote:
>>>>>
>>>>>>bspear78 wrote:
>>>>>>> I have a check engine light on, and the code is reading a 12 and a
>>>>>>> 72.
>>>>>>> I know what the 12 means, but could not find any explanation for a
>>>>>>> reading of 72. Anyone know what this means?
>>>>>>
>>>>>>72 Catalyst efficiency below required level. (Same as code 64)
>>>>>>
>>>>>>This means one of two things.
>>>>>>1) your catalytic converter is plugging/cracking/failing
>>>>>>2) the O2 sensor behind the cat is failing
>>>>>
>>>>> If the downstream O2 was failing you'd get a downstream O2 fault, not
>>>>> a cat efficiency fault.
>>>>>
>>>>
>>>>I'm not sure that is true in an OBD I car. The CAT is not a likely
>>>>source
>>>>of
>>>>problems, and my money is on the after-CAT sensor going bad.
>>>
>>> An OBD I jeep wouldn't even have a downstream O2 sensor. You just lost
>>> your money.
>>>
>>>>
>>>>I am pretty sure that the downstream sensor can give an error that says
>>>>the
>>>>CAT is failing. This can happen because the system doesn't know that the
>>>>sensor is bad, it only knows that the input from the sensor is not
>>>>correct.
>>>>The sensor can fail in a mode that makes the system say that the CAT is
>>>>not
>>>>working when the reality is that the sensor itself has taken a bye.
>>>
>>> Wrong. A failed downstream sensor will not set a cat efficiency fault.
>>> In fact, the poorer the downstream sensor functions, the less likely a
>>> cat fault would result.
>>>
>>>>
>>>>Having said all of that, the OP says he has a 97 YJ. In the 97, it was
>>>>called a TJ, and in 97, the codes are OBD II.
>>>
>>> A 1997 vehicle would be OBD II, no matter what it was called, or who
>>> made it.
>>>
>>
>>Well, then we're all chasing our shadows. Because, an OBD II car won't
>>have
>>a Code 72 ...
>
> Oh really? Please tell us how you came to that conclusion.
>

Which conclusion?

OBD II specs say that the code will be something like P0440, where there is
an alpha digit followed by 4 numeric digits. 72 does not fit the spec.

Would you like the link to the OBD II spec?

Re: check engine light on in 97 wrangler YJ with error code reading 72
 

"bllsht" <nospam@dot.net> wrote in message
news:51j0r2lejqa7apj35s5jhrni154b3c4vq0@4ax.com...
>
>
>
> You're both leaping to conclusions without even having a clue as to
> how the PCM determines the cat converter's efficiency.
>

I'm not leaping to anything. If you would like to tell us how ti works, go
ahead. but, my guess is that it will boil down nicely to, "what comes out of
the CAT is not correct relative to what went in."

If what goes into the CAT is not correct, then there is a code that
specifies this condition. What comes out might not be correct, but if what
wen it was not correct first, that is the code to fix. If there is no code
addressing the condition of what goes into the CAT, but there is one that
addresses what comes out, I'll put my money on the sensor as the first and
foremost most likely suspect.

Re: check engine light on in 97 wrangler YJ with error code reading 72
 

"bllsht" <nospam@dot.net> wrote in message
news:51j0r2lejqa7apj35s5jhrni154b3c4vq0@4ax.com...
>
>
>
> You're both leaping to conclusions without even having a clue as to
> how the PCM determines the cat converter's efficiency.
>

I'm not leaping to anything. If you would like to tell us how ti works, go
ahead. but, my guess is that it will boil down nicely to, "what comes out of
the CAT is not correct relative to what went in."

If what goes into the CAT is not correct, then there is a code that
specifies this condition. What comes out might not be correct, but if what
wen it was not correct first, that is the code to fix. If there is no code
addressing the condition of what goes into the CAT, but there is one that
addresses what comes out, I'll put my money on the sensor as the first and
foremost most likely suspect.

Re: check engine light on in 97 wrangler YJ with error code reading 72
 

"bllsht" <nospam@dot.net> wrote in message
news:51j0r2lejqa7apj35s5jhrni154b3c4vq0@4ax.com...
>
>
>
> You're both leaping to conclusions without even having a clue as to
> how the PCM determines the cat converter's efficiency.
>

I'm not leaping to anything. If you would like to tell us how ti works, go
ahead. but, my guess is that it will boil down nicely to, "what comes out of
the CAT is not correct relative to what went in."

If what goes into the CAT is not correct, then there is a code that
specifies this condition. What comes out might not be correct, but if what
wen it was not correct first, that is the code to fix. If there is no code
addressing the condition of what goes into the CAT, but there is one that
addresses what comes out, I'll put my money on the sensor as the first and
foremost most likely suspect.