I recently replaced my O2 sensor with a universal one. It seemed to have
fixed the problems temporarily.

I'm still getting errors 12 & 21. Power loss & O2 sensor problem.
I think there's a second sensor. Can this be the cause.
Also, is the 'power loss' error from the possibility that the sensor has a
bad connection.

--
Mel P.
96 Cherokee

 

Mel P. did pass the time by typing:
> I recently replaced my O2 sensor with a universal one. It seemed to have
> fixed the problems temporarily.

Year, engine, model?

> I'm still getting errors 12 & 21. Power loss & O2 sensor problem.
> I think there's a second sensor. Can this be the cause.
> Also, is the 'power loss' error from the possibility that the sensor has a
> bad connection.

You can clear the 21 code by disconnecting the battery for about 10 min
then putting it back on. That of course sets code 12 again though.

12 just means the battery has been disconnected at one time and the
jeep hasn't been started fifty times yet to clear it. Generally if
it isn't surrounded by a lot of other codes it's meaningless. If it
comes with boatloads of sensor fault codes it usually means the battery
terminal or cable is loose.

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."

so, that means one of a few things.
- if you have two sensors, the other one might be bad
- the relay that sends 12V to pre-heat the sensor or it's
associated fuse might be bad
- the harness where it clamps onto the side of the I6 might
have melted though and shorted out.
- check the whole harness for any melt spots.

--
DougW

 

Mel P. did pass the time by typing:
> I recently replaced my O2 sensor with a universal one. It seemed to have
> fixed the problems temporarily.

Year, engine, model?

> I'm still getting errors 12 & 21. Power loss & O2 sensor problem.
> I think there's a second sensor. Can this be the cause.
> Also, is the 'power loss' error from the possibility that the sensor has a
> bad connection.

You can clear the 21 code by disconnecting the battery for about 10 min
then putting it back on. That of course sets code 12 again though.

12 just means the battery has been disconnected at one time and the
jeep hasn't been started fifty times yet to clear it. Generally if
it isn't surrounded by a lot of other codes it's meaningless. If it
comes with boatloads of sensor fault codes it usually means the battery
terminal or cable is loose.

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."

so, that means one of a few things.
- if you have two sensors, the other one might be bad
- the relay that sends 12V to pre-heat the sensor or it's
associated fuse might be bad
- the harness where it clamps onto the side of the I6 might
have melted though and shorted out.
- check the whole harness for any melt spots.

--
DougW

 

Mel P. did pass the time by typing:
> I recently replaced my O2 sensor with a universal one. It seemed to have
> fixed the problems temporarily.

Year, engine, model?

> I'm still getting errors 12 & 21. Power loss & O2 sensor problem.
> I think there's a second sensor. Can this be the cause.
> Also, is the 'power loss' error from the possibility that the sensor has a
> bad connection.

You can clear the 21 code by disconnecting the battery for about 10 min
then putting it back on. That of course sets code 12 again though.

12 just means the battery has been disconnected at one time and the
jeep hasn't been started fifty times yet to clear it. Generally if
it isn't surrounded by a lot of other codes it's meaningless. If it
comes with boatloads of sensor fault codes it usually means the battery
terminal or cable is loose.

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."

so, that means one of a few things.
- if you have two sensors, the other one might be bad
- the relay that sends 12V to pre-heat the sensor or it's
associated fuse might be bad
- the harness where it clamps onto the side of the I6 might
have melted though and shorted out.
- check the whole harness for any melt spots.

--
DougW

 

Mel P. did pass the time by typing:
> I recently replaced my O2 sensor with a universal one. It seemed to have
> fixed the problems temporarily.

Year, engine, model?

> I'm still getting errors 12 & 21. Power loss & O2 sensor problem.
> I think there's a second sensor. Can this be the cause.
> Also, is the 'power loss' error from the possibility that the sensor has a
> bad connection.

You can clear the 21 code by disconnecting the battery for about 10 min
then putting it back on. That of course sets code 12 again though.

12 just means the battery has been disconnected at one time and the
jeep hasn't been started fifty times yet to clear it. Generally if
it isn't surrounded by a lot of other codes it's meaningless. If it
comes with boatloads of sensor fault codes it usually means the battery
terminal or cable is loose.

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."

so, that means one of a few things.
- if you have two sensors, the other one might be bad
- the relay that sends 12V to pre-heat the sensor or it's
associated fuse might be bad
- the harness where it clamps onto the side of the I6 might
have melted though and shorted out.
- check the whole harness for any melt spots.

--
DougW