Contaminated A/F Sensor - Advice Requested
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Pit Crew
Joined: Jul 2010
Posts: 126
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From: Hawaii
Contaminated A/F Sensor - Advice Requested
Hello All,
I recently replaced the front valve cover seal on my 99 RX300. In order to make more room I disconnected the coolant hose that runs over the valve cover. Some coolant came out but not an excessive amount. I removed the cover and in my attempt to keep the hose running from radiator vertical, some coolant spilled into the valve area and probably a bit into the oil passageway leading to the oil pan. I cleaned the surface, put fresh beads of Toyota FIPG sealant, and closed everything up. I then changed the oil and filter, because it needed it and to hopefully deal with any coolant that may have gotten in the oil.
A few day later I started getting P1135 and P0125 (I understand now is most likely a false code) codes. Like most I was distracted by the P0125 code and thought it was due to my coolant loss or possibly air in the coolant system. After some extensive research on this site I now understand that my issue is the Bank 1 Sensor 1 A/F Sensor. I could not wrap my head around how what I did to replace the cover could lead to that code until I read the following from Denso on the RockAuto site.
Oxygen (O2) Sensors commonly fail due to contamination. When checking or replacing an O2 Sensor, visually inspect the sensor body to determine if it has been contaminated by a faulty part or substance upstream, and correct the fault before replacing the sensor.
One of the possible reasons is an incorrect sealant, which I don't believe is the case considering I used OEM Toyota sealant. The other is related to coolant (antifreeze) contamination. Has anyone else heard or experienced this issue? My concern is if the sensor was contaminated by coolant, and I stick a new sensor in, will that also be contaminated? Should I run the car a bit longer in hopes to burn out any contaminants, then put a new sensor? Can the sensor be cleaned to get it working again or has the coolant caused the sensor to short?
Thanks
I recently replaced the front valve cover seal on my 99 RX300. In order to make more room I disconnected the coolant hose that runs over the valve cover. Some coolant came out but not an excessive amount. I removed the cover and in my attempt to keep the hose running from radiator vertical, some coolant spilled into the valve area and probably a bit into the oil passageway leading to the oil pan. I cleaned the surface, put fresh beads of Toyota FIPG sealant, and closed everything up. I then changed the oil and filter, because it needed it and to hopefully deal with any coolant that may have gotten in the oil.
A few day later I started getting P1135 and P0125 (I understand now is most likely a false code) codes. Like most I was distracted by the P0125 code and thought it was due to my coolant loss or possibly air in the coolant system. After some extensive research on this site I now understand that my issue is the Bank 1 Sensor 1 A/F Sensor. I could not wrap my head around how what I did to replace the cover could lead to that code until I read the following from Denso on the RockAuto site.
Oxygen (O2) Sensors commonly fail due to contamination. When checking or replacing an O2 Sensor, visually inspect the sensor body to determine if it has been contaminated by a faulty part or substance upstream, and correct the fault before replacing the sensor.
One of the possible reasons is an incorrect sealant, which I don't believe is the case considering I used OEM Toyota sealant. The other is related to coolant (antifreeze) contamination. Has anyone else heard or experienced this issue? My concern is if the sensor was contaminated by coolant, and I stick a new sensor in, will that also be contaminated? Should I run the car a bit longer in hopes to burn out any contaminants, then put a new sensor? Can the sensor be cleaned to get it working again or has the coolant caused the sensor to short?
Thanks
