check engine light on in 97 wrangler YJ with error code reading 72
01-16-2007, 09:20 PM
#21
Guest
Posts: n/a
Re: check engine light on in 97 wrangler YJ with error code reading 72
DougW wrote:
> 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.
Actually that just made me think... if the forward O2 sensor
is weak, the rear O2 sensor may very well call out a bad cat
because the engine will be running rich.
Too bad there isn't an easy way to test O2 sensors.
--
DougW
> 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.
Actually that just made me think... if the forward O2 sensor
is weak, the rear O2 sensor may very well call out a bad cat
because the engine will be running rich.
Too bad there isn't an easy way to test O2 sensors.
--
DougW
01-17-2007, 01:51 AM
#22
Guest
Posts: n/a
Re: check engine light on in 97 wrangler YJ with error code reading 72
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.com.. .
>> 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.
>
>
>
>
>
<crwlr@verizon.net> wrote:
>
>"bllsht" <nospam@dot.net> wrote in message
>news:567mq2lcmmf2td23fj2mo0bsfndgffg805@4ax.com.. .
>> 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.
>
>
>
>
>
01-17-2007, 01:51 AM
#23
Guest
Posts: n/a
Re: check engine light on in 97 wrangler YJ with error code reading 72
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.com.. .
>> 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.
>
>
>
>
>
<crwlr@verizon.net> wrote:
>
>"bllsht" <nospam@dot.net> wrote in message
>news:567mq2lcmmf2td23fj2mo0bsfndgffg805@4ax.com.. .
>> 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.
>
>
>
>
>
01-17-2007, 01:51 AM
#24
Guest
Posts: n/a
Re: check engine light on in 97 wrangler YJ with error code reading 72
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.com.. .
>> 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.
>
>
>
>
>
<crwlr@verizon.net> wrote:
>
>"bllsht" <nospam@dot.net> wrote in message
>news:567mq2lcmmf2td23fj2mo0bsfndgffg805@4ax.com.. .
>> 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.
>
>
>
>
>
01-17-2007, 01:51 AM
#25
Guest
Posts: n/a
Re: check engine light on in 97 wrangler YJ with error code reading 72
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.com.. .
>> 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.
>
>
>
>
>
<crwlr@verizon.net> wrote:
>
>"bllsht" <nospam@dot.net> wrote in message
>news:567mq2lcmmf2td23fj2mo0bsfndgffg805@4ax.com.. .
>> 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.
>
>
>
>
>
01-17-2007, 01:52 AM
#26
Guest
Posts: n/a
Re: check engine light on in 97 wrangler YJ with error code reading 72
On Tue, 16 Jan 2007 17:23:58 -0600, "DougW"
<post.replies@invalid.address> wrote:
>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.
Nice assumption, but that's not the way it works.
<post.replies@invalid.address> wrote:
>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.
Nice assumption, but that's not the way it works.
01-17-2007, 01:52 AM
#27
Guest
Posts: n/a
Re: check engine light on in 97 wrangler YJ with error code reading 72
On Tue, 16 Jan 2007 17:23:58 -0600, "DougW"
<post.replies@invalid.address> wrote:
>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.
Nice assumption, but that's not the way it works.
<post.replies@invalid.address> wrote:
>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.
Nice assumption, but that's not the way it works.
01-17-2007, 01:52 AM
#28
Guest
Posts: n/a
Re: check engine light on in 97 wrangler YJ with error code reading 72
On Tue, 16 Jan 2007 17:23:58 -0600, "DougW"
<post.replies@invalid.address> wrote:
>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.
Nice assumption, but that's not the way it works.
<post.replies@invalid.address> wrote:
>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.
Nice assumption, but that's not the way it works.
01-17-2007, 01:52 AM
#29
Guest
Posts: n/a
Re: check engine light on in 97 wrangler YJ with error code reading 72
On Tue, 16 Jan 2007 17:23:58 -0600, "DougW"
<post.replies@invalid.address> wrote:
>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.
Nice assumption, but that's not the way it works.
<post.replies@invalid.address> wrote:
>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.
Nice assumption, but that's not the way it works.
01-17-2007, 02:05 AM
#30
Guest
Posts: n/a
Re: check engine light on in 97 wrangler YJ with error code reading 72
On Tue, 16 Jan 2007 20:20:41 -0600, "DougW"
<post.replies@invalid.address> wrote:
>DougW wrote:
>
>> 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.
>
>Actually that just made me think... if the forward O2 sensor
>is weak, the rear O2 sensor may very well call out a bad cat
>because the engine will be running rich.
Never seen an O2 fail causing a lean condition?
>
>Too bad there isn't an easy way to test O2 sensors.
Very easy with a DSO.
<post.replies@invalid.address> wrote:
>DougW wrote:
>
>> 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.
>
>Actually that just made me think... if the forward O2 sensor
>is weak, the rear O2 sensor may very well call out a bad cat
>because the engine will be running rich.
Never seen an O2 fail causing a lean condition?
>
>Too bad there isn't an easy way to test O2 sensors.
Very easy with a DSO.