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
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. > > > > > |
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. > > > > > |
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. > > > > > |
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. > > > > > |
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. |
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. |
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. |
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. |
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. |
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