up stream o2 sensor.

so i got an 1999 cherokee sport a few weeks ago and a day or so after i got it the check engine light came on followed by a rough idle. every now and then it will chug and eventually die. :flamemad: so my uncle and i hooked it up to the computer and it said i had a short at both of the o2 sensors and a misfire on cylinder 3. the down stream had some wires frayed from rubbing on the drive shaft. fixed that and found no issues with the upstream. replaced the upstream and cleared the computer drove it a little ways and it came back on. repalced the downstream and cleared the comuter and the check engine light came back on followed by some new issues. at one point it wouldnt start with out any throttle or stay running with out throttle. that went away after a day or so. hooked it up today again and all the computer was saying is the upstream o2 sensor had a short. alswas saying it was running either rich or central. not bouncing between rich and lean. we cleared the computer again. and it started bouncing between rich and lean. i guess it sounds like a short and we followed the upstream sensors and cant find and bad wires. im trying to give you all as much information as possible and i guess im asking you guys what you think and where i should be checking for shorts.

Re: up stream o2 snesor.

Try this:

P0131-1/1 O2 SENSOR SHORTED TO GROUND

1. Turn the ignition off.
Disconnect the O2 Sensor harness connector.
Measure the resistance of the O2 Sensor Signal circuit (Pin 4, Black wire / Dark Green tracer) in the O2 Sensor harness
connector to ground.
Is the resistance below 100 ohms?

Yes - Repair the O2 Sensor Signal circuit for a short to ground.

No - Go To 2.

2. Turn the ignition off.
Disconnect the O2 Sensor harness connector.
Measure the resistance between the O2 Sensor Signal circuit (Pin 4, Black wire / Dark Green tracer) and the Sensor ground (Pin 3, Brown wire / Yellow tracer) circuit in the O2 Sensor harness connector.
Is the resistance below 100 ohms?

Yes - Repair the O2 Sensor Signal circuit for a short to the Sensor
ground circuit.

No - Go To 3.
TEST ACTION APPLICABILITY
3. Turn the ignition off.
Disconnect the O2 Sensor harness connector.
Measure the resistance between the O2 Sensor Signal circuit (Pin 4, Black wire / Dark Green tracer) and the Heater ground circuit (Pin 2, Black wire) in the O2 Sensor harness connector.
Is the resistance below 100 ohms?

Yes - Repair the O2 Sensor Signal circuit for a short to the Heater
ground circuit.

all right all start following these steps. thanks for the help!!:worship: