Touble Shoot 02 Sensor

[steve56]

Well you have proven the heater is bad on your sensor. That is about the end of the story for that sensor at least. The Fluke knows.

Thanks for your imput. I am  getting conflicting data from my Actron meter and my Fluke meter. I think your correct. The Actron data might be too generic, however an amp reading from a Fluke meter is pretty unambiguous.

[steve56]

Well you have proven the heater is bad on your sensor. That is about the end of the story for that sensor at least. The Fluke knows.

Thanks for your input. Im getting conflicting data from my Actron meter saying heater circuit good and my Fluke saying heater circuit is bad. I can see the Actron data meter being more ambiguous than the Fluke data.I'm still looking a known good used four wire A/F sensor that I can put in the car to verify whats going on. 

[Cougar]

There is absolutely no doubt that the heater is bad in the sensor. The Fluke has spoken and it has the last word, no matter what any other device says is going on. The difference between 1 ohm and OPEN is almost the same difference as a short and a open is. The sensor is bad, period.

[steve56]

There is absolutely no doubt that the heater is bad in the sensor. The Fluke has spoken and it has the last word, no matter what any other device says is going on. The difference between 1 ohm and OPEN is almost the same difference as a short and a open is. The sensor is bad, period.

Appreciate your help. A/F O2 sensors are new to me. I've only dealt with Subaru narrow band sensors.

[Cougar]

The heater must have some fairly low DC resistance so current can flow through it and generate heat. If the circuit is open no current can flow. No current flow, no heat. It is that simple.

[steve56]

One more unresolved issue.

 

Just talked to GTC which is a Canadian Co. that makes O2 test equipment. Their tech said the heaters circuit in A/F sensors just speed up the heating process and the Cat. Converter would have the A/F sensor to operating temp. even if the heater circuit was broken. I already thought that ws the case, just got it confirmed.

 

Now I need to know if a bad heater cicuit would trigger a CEL light and not let the fuel system go into closed loop even when the A/F sensor is up to temp. He also thought that my O2S11(v) being statisc at 3.797.on a live data screen on my Actron monitor looked like another circuit in the sensor might ultimately be the cause of my P1133 trouble code. Didnt know how Subaru software was set up though.

[Cougar]

The P1133 code will go away once a new sensor is installed and the wiring to the sensor is okay. As for the data of 02S11 making a change that is another matter. I'm not even sure that is the same sensor that has the damaged heater. The  S11 should tell you which sensor is supplying that data. If you don't know then disconnect the sensors one at a time and see when the data drops off or changes on that sensor data.  

[steve56]

The P1133 code will go away once a new sensor is installed and the wiring to the sensor is okay. As for the data of 02S11 making a change that is another matter. I'm not even sure that is the same sensor that has the damaged heater. The  S11 should tell you which sensor is supplying that data. If you don't know then disconnect the sensors one at a time and see when the data drops off or changes on that sensor data.  

Yes, I will unplug the upstream sensor to verify. With every other Subaru using my Actron meter my asumption was that OS11(v) was the upstream sensor and OS12(V) was the downstream sensor. I thought OS11(v) stood for bank one sensor one (pre cat. converter voltage), and OS12(v) stood for bank one sensor two (post cat. converter voltage). Also I'm learing that with A/F sensors the (v) displayed on my Actron meter is interpretive data and that the ecm is actually reacting to micro amp changes in the sensor. The Actron interprets the micro apm changes as volts to make it (easier) to read.

[Cougar]

Your previous statements seem pretty much the way I understand things also. The scanner voltage reading should be the voltage that sensor was generating at the time the reading was done by the scanner. 

[steve56]

The P1133 code will go away once a new sensor is installed and the wiring to the sensor is okay. As for the data of 02S11 making a change that is another matter. I'm not even sure that is the same sensor that has the damaged heater. The  S11 should tell you which sensor is supplying that data. If you don't know then disconnect the sensors one at a time and see when the data drops off or changes on that sensor data.  

Disconnected the upstream O2 sensor, tried clearing the P1133 code but the OS11(v) of 3.797 is still on the Actron. It looks like a permanent code is being stored in the ecm until a new O2  sensor is installed or...?

[Fairtax4me]

That could just be a default voltage that the ECU shows if the sensor fails. Or the scanner may be set to display AF sensor voltage, but the front sensor is actually a plain oxygen sensor.

[steve56]

That could just be a default voltage that the ECU shows if the sensor fails. Or the scanner may be set to display AF sensor voltage, but the front sensor is actually a plain oxygen sensor.

I wish it was a plain 02 Sensor, but the FSM calls for a A/F sensor and they are over $100. I had never even heard of an A/F sensor.

Edited May 6, 2016 by steve56

[steve56]

There is absolutely no doubt that the heater is bad in the sensor. The Fluke has spoken and it has the last word, no matter what any other device says is going on. The difference between 1 ohm and OPEN is almost the same difference as a short and a open is. The sensor is bad, period.

Yes it was just a bad O2sensor. Replaced sensor and engine went into closed loop and both fuel trims and O2 sensors started showing live data. The live data voltage on this wide band sensor doesn't vary between .1and .9 volts. llike the narrow band sensor. The wide band sensor sends small amp changes to ecm to change fuel trims and sends an interpretive voltage reading to the meter of around 3 volts. Before changing the sensor I was getting an upstream voltage reading of 3.797 (v) and a heater circuit ok message. 

 

Like you said though the Fluke doesnt lie. It tested the bad sensor which had an OL reading on heater circuit  and the new sensor with 1(v) reading on heater circuit. I went through the whole diagnosic process to learn how to trouble shoot more effectively. Thank for eveyones input.

[HANBHO]

New member here...

 

CEL (P1133) come ON right away after erasing CEL..

 

Replaced front O2 with new OEM..no joy.

Replace another ECM.. no joy.

 

Looks like short somewhere.. 

Anyone had a same problem?

Any tip to troubleshoot further would be big help.

 

Thanks,

Han