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O2 sensor issues?

Old 05-09-2019, 07:19 PM
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Default O2 sensor issues?

This 3:31 minute video shows 90 cherokee o2 sensor, fuel trim, loop status, exaust condition, and Map sensor voltage.

Cold start o2 reads almost 5 volts and stays fairly stead slowly drops as engine warms.
St fuel trim stays at 128 while in open loop.
ST fuel trim bounces while in closed loop.
Engine RPM changes with open/closed loop.
Exaust never goes rich/lean. Stays lean when engine is cold as well as warm.

Note: ST fuel trim and loop status changes ONLY for the first 1 and 1/2 minutes into video then stays steady.
Map sensor voltage fairly steady while in open loop, then jumps around while in closed loop.
Map sensor vacuum moves a lot.

This 1:05 minute video shows engine after warm.


O2 sensor voltage slowly decreases as engine gets warmer.
Fuel trims stay at 128.
Loop status stays open.
Exaust stays lean.

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Old 05-09-2019, 08:20 PM
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O2 sensor isn't sending a good signal. Exhaust should read rich/Lean real rapidly.
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Old 05-09-2019, 10:10 PM
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I noticed when I pulled the o2 sensor relay there was a jumper wire from the o2 sensor relay to the fuel pump relay.
When I took out the the jumper wire the fuel pump would not run.
And leaving the jumper wire intact and removing the fuel pump relay the fuel pump kept working because the pump was getting power from the o2 sensor relay.

Would that effect the o2 sensor?
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Old 05-09-2019, 10:32 PM
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Originally Posted by randy61 View Post
I noticed when I pulled the o2 sensor relay there was a jumper wire from the o2 sensor relay to the fuel pump relay.
When I took out the the jumper wire the fuel pump would not run.
And leaving the jumper wire intact and removing the fuel pump relay the fuel pump kept working because the pump was getting power from the o2 sensor relay.

Would that effect the o2 sensor?

The heater circuit being bad in the sensor or not getting power. Or ground. somebody monkeyed with wiring. You better check for voltage at the orange wire at the sensor, good ground from the black wire to engine, resistance across orange wire and black wire at the sensor with it unplugged from the harness.
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Old 05-09-2019, 11:26 PM
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I checked the o2 ohms between the red power wire and black wire, o2 unplugged from harness. Got a reading of 1060 if that's possible. Could not see if there was a period in there due to being underneath the vehicle. That was with the sensor still in the exhaust.

you said: "check for voltage at the orange wire at the sensor, good ground from the black wire to engine".

Are you referring to the engine side harness, orange and two black? The sensor plug has red, black and gray.



Last edited by randy61; 05-10-2019 at 02:08 AM. Reason: corrections
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Old 05-10-2019, 07:07 AM
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Originally Posted by r
andy61;3555059
I checked the o2 ohms between the red power wire and black wire, o2 unplugged from harness. Got a reading of 1060 if that's possible. Could not see if there was a period in there due to being underneath the vehicle. That was with the sensor still in the exhaust.

you said: "check for voltage at the orange wire at the sensor, good ground from the black wire to engine".

Are you referring to the engine side harness, orange and two black? The sensor plug has red, black and gray.
Engine side red and black. Red is power for the sensor heater, black is ground for the heater, and gray is sensor signal to ECU,

I think the ohms should be 8 to 13 or so
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Old 05-11-2019, 08:22 PM
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The jumper wire between the two relays are grounds. The o2 relay ground is jumped to the fuel pump relay ground with a short wire going between the two relay grounds.
That should not affect the o2 sensor function.
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Old 05-11-2019, 08:28 PM
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Default 87-90 Jeep Renix Oxygen Sensors (Why Hard To Find)

Writeup as to the difference in o2 sensor and why you cant find o2 sensors at the local part stores that will work on renix engines.

http://tomco-inc.com/Tech_Tips/ttt20.pdf
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Old 05-12-2019, 08:19 AM
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Originally Posted by randy61 View Post
The jumper wire between the two relays are grounds. The o2 relay ground is jumped to the fuel pump relay ground with a short wire going between the two relay grounds.
That should not affect the o2 sensor function.
Sensors can be found. test yours as I described a few posts up.
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Old 05-12-2019, 08:55 PM
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Originally Posted by cruiser54 View Post
Engine side red and black. Red is power for the sensor heater, black is ground for the heater, and gray is sensor signal to ECU,

I think the ohms should be 8 to 13 or so

Key on engine off - Engine side o2 plug, Orange wire 12v, black ground wire 0v and grey wire 5v.
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Old 05-12-2019, 09:10 PM
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Originally Posted by randy61 View Post
Key on engine off - Engine side o2 plug, Orange wire 12v, black ground wire 0v and grey wire 5v.

Key off and sensor unplugged. Check the black wire ohms to ground.

then check ohms orange to black on the sensor.
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Old 05-13-2019, 12:40 PM
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Originally Posted by cruiser54 View Post
Key off and sensor unplugged. Check the black wire ohms to ground.

then check ohms orange to black on the sensor.

Key off sensor unplugged black wire tested 0 ohms.

Sensor unplugged orange to black reads 0L.

Engine side everything tests okay. Its obvious sensor is bad.


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Old 05-13-2019, 04:13 PM
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Originally Posted by randy61 View Post
Key off sensor unplugged black wire tested 0 ohms.

Sensor unplugged orange to black reads 0L.

Engine side everything tests okay. Its obvious sensor is bad.

Yup.
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Old 05-13-2019, 05:03 PM
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Now its just a matter of finding a o2 sensor that don't cause almost a 2 amp parastic draw.

Tried a NGK 23553 and Bosch 12009 from my local part stores. Part store computer showed the original sensor (white body black boot covering the red, black and grey wires). The employees at each store, oreillys, pepboys, come out with a metal bodied sensors. Figured they would work being they were replacement parts. Nope, caused battery draw.

I then ordered a Walker. 250-23501 website showed (white body black boot covering the red, black and grey wires). Opened box and got a metal body. Failed on the Bosch, NGK and walker.

Then one I have now is off an 89 or 90 at the junk yard. Its no good.

Called a local 4x4 jeep salvage and was told the replacement was Crown Automotive 53004245. Ordered it from Quadratech, other online part stores have the same sensor part # (white body black boot covering the red, black and grey wires. Get it Wednesday so will see if its a metal body also.

2:45 into this video shows correct sensor from Walker. Packaging shows metal body but inside the box is the correct sensor (white body black boot covering the red, black and grey wires). But this was in 2012. Something has change since, putting sensors in wrong boxes???
Walker O2 sensor

Last edited by randy61; 05-13-2019 at 05:07 PM. Reason: correction
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Old 05-13-2019, 05:35 PM
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When you're at the junkyard, carry your meter. Check between the orange and black wires before taking the sensor.

The NTKs used to be the correct replacements.
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