got check engine code 21

[rufus_1111]

so i have a 97 and i got the codes by doing the key on/off thing. i got code 12 and 21. i looked the codes up to see what they mean and for 21 i got whats below....what does it mean? do i need both O2 sensors or what?


Code 21-Upstream oxygen sensor response slower than minimum required switching frequency. Upstream oxygen sensor heating element circuit malfunction. Downstream oxygen sensor heating element circuit malfunction. Downstream oxygen sensor input voltage maintained above the normal operating range. Oxygen sensor voltage too low, tested after cold start. (Upstream or Downstream) Left oxygen sensor input voltage maintained above the normal operating temperature.

 

[Matthew Currie]

If possible I think you should go get an OBDII reading on that. I'm pretty sure the OBDII codes will cut it a little finer and will tell you which sensor is actually at fault. They do on the 99.

 

[rufus_1111]

Any other ideas

 

[rufus_1111]

well i went out yesterday and got the upstream o2 sensor. then i was driving it lastnight and the check egine light comes on again. so does that mean it is the downstream o2 sensor?

 

[Cruzzin_XJ]

What ended up being the fix for this, i have a 97 with the same code

Engine runs fine for 10 minutes and then starts to studder and loses some power. Also stalls at idle?

Thanks

 

[birchlakeXJ]

I agree with Matthew on getting an OBD2 reading. The 2 digit code you get from key on key off is pretty vague. Use the technology your Jeep provides to you. Also, be sure to check for burnt/damaged wires for O2 problems.

 

[dagr8tim]

Not to drag up an old thread, but I figured it was easier than starting a new thread.

My 97 has error code 12 & 21. My issue is the PO removed the cat. Is there an O2 sensor downstream of the cat?

 

[hubs97xj]

Yep- the second sensor is normally right after the cat.

 

[dagr8tim]

Yep- the second sensor is normally right after the cat.

And the cat is under the pass side, basically under the passenger seat?

 

[lawsoncl]

Not to drag up an old thread, but I figured it was easier than starting a new thread.

My 97 has error code 12 & 21. My issue is the PO removed the cat. Is there an O2 sensor downstream of the cat?

Well if you just bought it, you can force the PO to have a cat and rear O2 sensor installed. Just threaten him with this http://www.epa.state.oh.us/dapc/echeck/docs/tamper_law.pdf.

Did you know that Federal law actually forbids not just removing, but even replacing a functioning cat converter? http://www.catalyticconverter.org/law/index.htm Guess that means installing a hi-flow unit in place of a working stock unit would also be illegal.

 

[dagr8tim]

Well if you just bought it, you can force the PO to have a cat and rear O2 sensor installed. Just threaten him with this http://www.epa.state.oh.us/dapc/echeck/docs/tamper_law.pdf.

Did you know that Federal law actually forbids not just removing, but even replacing a functioning cat converter? http://www.catalyticconverter.org/law/index.htm Guess that means installing a hi-flow unit in place of a working stock unit would also be illegal.

I was aware of the federal laws regarding converters, and that among other things junk yards cannot resell them. Ohio doesn't have inspections or anything to worry about. I just want to get rid of the annoying CEL.

I think I found an OE replacement on ebay, and the sensor from autozoo/advance. I'm just gonna have to pony up about $150 for the parts.

 

[kennzz05]

suprised noones mentioned this but obII cant be read with the key on ,off way you need a code reader hooked to the port by your left knee under the dash

 

[hubs97xj]

And the cat is under the pass side, basically under the passenger seat?

Yep, the cat is normally located right after the pipe passes through the crossmember.

 

[lawsoncl]

suprised noones mentioned this but obII cant be read with the key on ,off way you need a code reader hooked to the port by your left knee under the dash

Some of the 96 and 97 years could still do the key on-off trick and get the obdi version of the codes.

 

[dagr8tim]

Some of the 96 and 97 years could still do the key on-off trick and get the obdi version of the codes.

On mine, not only did the CEL flash the codes, but the code was displayed on the digital odo.

 

[dagr8tim]

One more quick question. I got up under my jeep today and couldn't find the rear O2 harness. I found a plastic bracket near the front universal on the rear drive shaft, buy no wires. The only wiring bundle I could find in that area looked like it went to the rear of the tranny/top of the transfer case.