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Re: check engine light on in 97 wrangler YJ with error code reading 72
"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. 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. |
Re: check engine light on in 97 wrangler YJ with error code reading 72
"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. 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. |
Re: check engine light on in 97 wrangler YJ with error code reading 72
"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. 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. |
Re: check engine light on in 97 wrangler YJ with error code reading 72
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. -- DougW |
Re: check engine light on in 97 wrangler YJ with error code reading 72
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. -- DougW |
Re: check engine light on in 97 wrangler YJ with error code reading 72
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. -- DougW |
Re: check engine light on in 97 wrangler YJ with error code reading 72
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. -- DougW |
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 |
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 |
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 |
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