Oxygen sensors

STEVEN HOFFMAN

MEMBER
2000 FORD MUSTANG
3.8L
V6
2WD
AUTOMATIC
152,400 MILES

So I had an issue with my drive cycle not wanting to complete. The evap monitor, the catalyst monitor, the oxygen sensor monitor and the oxygen sensor heater monitor are all incomplete. There were no fault codes or pending fault codes showing. So I monitored my oxygen sensors using a obd2 scan tool and saw that both of the downstream oxygen sensors were showing 0.0 voltage. So I tested them with a multi-meter and they were both producing 0.01 volts from the signal wire. I read that they should produce between 0.1 and 0.9 volts. So I replaced them both with brand new downstream oxygen sensors that I bought from 1aauto. Com. I took my car out for a drive and scanned it to see if the drive cycle completed. It did not complete, however I also checked for pending fault codes and it threw back two p0141 and p0161. I searched on online to see what these codes mean. According to what I found they mean the same thing just one is for bank 1 sensor 2 and the other is bank 2 sensor 2. They mean that there is either a short circuit in the heater circuit or that there is excessive resistance in the heater circuit. So what do I do now? Do I contact 1aauto. Com to return them? What are the chances of buying two new oxygen sensors and they both be faulty? Or is it something else maybe?

Thursday, October 3rd, 2019 AT 1:33 PM

5 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good afternoon.

Were the sensor direct replacement sensors? Were they the ones you had to wire in or did they have connectors on them?

I attached or posted the possible reasons for the code. Since these codes did not set prior to the replacement of the sensors, I think it is an issue with the sensors.

They should read around.5 volts constantly. They will not vary like the front sensors. There only purpose is to monitor the cat converters. If the sensor vary like the front, the cat converters are bad. It would set a 420 code if that was the case.

Get a good quality sensor. Do not go cheap. Quality matters with O2 sensors.

I also attached the drive cycle for you to follow when you are finished. Make sure you clear the codes before performing the drive cycle.

Roy

141

P0141
Descriptor
Ho2S Sensor Circuit Malfunction (Ho2S-125)
Probable Causes
Ground Circuit Open
Harness or Heated Oxygen Sensor (HO2S) Short to Ignition Switched Power (VPWR)
Heated Oxygen Sensor (HO2S) Heater Damaged
Ignition Switched Power (VPWR) Circuit Open
Low Battery Voltage
Poor Mating Terminals and Wiring or Corrosion
Powertrain Control Module (PCM) Damaged
Water in Harness Connector

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Thursday, October 3rd, 2019 AT 1:53 PM

BMDOUBLE

MECHANIC
1,139 POSTS

Yes I would return those sensors because if the monitors for the heaters and sensors completed without setting a dtc then the pcm did not see an issue there. These sensors should stay at a steady.4-.6 volts at idle after the vehicle has warmed up. Now they will in fact show 0 on cold starts because they are post catalyst and do not see the amount of fuel that the pre cat converters do. If there were an issue with the heater circuit it would have set a code for all four sensors, and if there were an issue with the circuit between the pcm and the sensor, 99% of the time it would only give you a code for one not both. So get those sensors changed out with good quality ones and let's go from there.

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Thursday, October 3rd, 2019 AT 2:03 PM

BMDOUBLE