Well, I got to use my new code reader today :(

[Huskymaniac]

Originally Posted by TomsSVX

You can see the trim numbers for bank #1 are high but less than 10% which is not all bad. Try to track down the service records for which sensor was replaced

Tom

After a rainy day yesterday, the O2 code was back. Was the rainy day a coincidence? Maybe. Here is the report:

Stored:
P0133 O2 Circuit Slow Response (Bank 1, Sensor 1)

Pending:
P0133 O2 Circuit Slow Response (Bank 1, Sensor 1)


MIL ON
Misfire Monitoring Complete
Fuel System Monitoring Complete
Comprehensive Component Monitoring Complete
Catalyst Monitoring Complete
Heated Catalyst Monitoring Not Supported
Evaporative System Monitoring Not Supported
Secondary Air System Monitoring Not Supported
A/C System Refrigerant Monitoring Not Supported
Oxygen Sensor Monitoring Not Complete
Oxygen Sensor Heater Monitoring Not Complete
EGR System Monitor Not Complete

DTC for which Freeze Frame was Stored P0133
Fuel System 1 Status Closed Loop
Fuel System 2 Status Closed Loop
Calculated LOAD Value 17.65 %
Engine Coolant Temp 87 °C (188.6F)
Short Term Fuel Trim - Bank 1 -2.34 %
Long Term Fuel Trim - Bank 1 11.72 %
Short Term Fuel Trim - Bank 2 0.78 %
Long Term Fuel Trim - Bank 2 2.34 %
Intake Manifold Absolute Pressure 53 kPa (7.687 psi)
Engine RPM 2487 rpm
Vehicle Speed Sensor 76 km/h (47.22 MPH)

So it looks like the long term trim is now greater than 10%. What is the difference in meaning between the long term trim and the short term trim and how does the ECU use them? Does a positive number mean extra fuel in the mix or extra air?

The previous owner has been unable to track down which sensor was replaced previously. So I will have my mechanic check for a corroded or bad connection and replace the sensor if the connection looks OK.

Exactly which sensor is Bank 1, sensor 1? And what does it mean when it says there is a slow response?

[kwren]

Originally Posted by Huskymaniac

After a rainy day yesterday, the O2 code was back. Was the rainy day a coincidence?

The Rainy day was in God's plan...

Does a positive number mean extra fuel in the mix or extra air?

Maybe "extra antifreze"

Keith


..................

[LetItSnow]

<Fuel trim info>

Had to look for myself.

[Huskymaniac]

Originally Posted by LetItSnow

<Fuel trim info>

Had to look for myself.

That's a nice detailed article. Thanks for actually adding something of value, as opposed to SOME people.

I found this one about "slow response" codes:

http://www.obd-codes.com/p0139

Basically, it says the possible causes are:

* The oxygen sensor is faulty
* The wiring to the sensor is broken / frayed
* There is an exhaust leak
* There is an inlet air leak
* The MAF sensor is not operating properly

Since my sensors are reading two very different things, the last two items are unlikely. The third one is also unlikely but easy to look for. I believe bank 1 is the passenger side? Bad connection or wiring to the sensor is also easy to look into. Then it is time to replace the sensor.

[Beav]

Kinda jumping in without reading all of tthe posts...

A little primer re: O2 sensors is first in order:

Typically common O2 sensors operate in a 0.1 volt to 0.9v range, 0.1v reflecting a lean a/f mixture and 0.9v rich a/f mixture. Midpoint would then be 0.45v and considered the 'transition' point or 'threshold' (between rich and lean.) Many people think that the ECU tunes the fuel to a static ratio but it doesn't. The O2 sensor 'sees' and reports a rich mixture (above the threshold) and the ECU responds by decreasing the injector 'on time' or dwell - measured in milliseconds. As a result the O2 sensor 'sees' and reports a lean condition and the ECU increases injector on time to compensate. So now you have an analog wave of rich to lean reporting by the O2 sensors and the corresponding ECU responses of increasing/decreasing injector dwell time.

In most cars (with multi-port injection) the peak-to-peak analog waves will occur 5-7 times per second. When O2 sensor performance degrades to roughly half that (each manufacturer can program the ECU to reflect adherence to EPA standards) the ECU will set a code for O2 performance. (Depending on year, make, model this may take several failures to actually set a code, allowing occasional flukes to not cause alarm.)

Since you seem to have issues related to water I would suspect cracked wiring near the sensor or failed weather shield at the connector, inhibiting its ability to send an accurate signal to the ECU. The O2 sensor also 'breathes' atmospheric O2 as a reference through its wiring (molecules' worth) and the wiring cannot be repaired for this reason.

[Huskymaniac]

Originally Posted by Beav

Kinda jumping in without reading all of tthe posts...

A little primer re: O2 sensors is first in order:

Typically common O2 sensors operate in a 0.1 volt to 0.9v range, 0.1v reflecting a lean a/f mixture and 0.9v rich a/f mixture. Midpoint would then be 0.45v and considered the 'transition' point or 'threshold' (between rich and lean.) Many people think that the ECU tunes the fuel to a static ratio but it doesn't. The O2 sensor 'sees' and reports a rich mixture (above the threshold) and the ECU responds by decreasing the injector 'on time' or dwell - measured in milliseconds. As a result the O2 sensor 'sees' and reports a lean condition and the ECU increases injector on time to compensate. So now you have an analog wave of rich to lean reporting by the O2 sensors and the corresponding ECU responses of increasing/decreasing injector dwell time.

In most cars (with multi-port injection) the peak-to-peak analog waves will occur 5-7 times per second. When O2 sensor performance degrades to roughly half that (each manufacturer can program the ECU to reflect adherence to EPA standards) the ECU will set a code for O2 performance. (Depending on year, make, model this may take several failures to actually set a code, allowing occasional flukes to not cause alarm.)

Since you seem to have issues related to water I would suspect cracked wiring near the sensor or failed weather shield at the connector, inhibiting its ability to send an accurate signal to the ECU. The O2 sensor also 'breathes' atmospheric O2 as a reference through its wiring (molecules' worth) and the wiring cannot be repaired for this reason.

Wow, thanks for the detailed technical response. My mechanic agrees that we should replace the sensor. I have the Bosch on order along with the host of fluids I intend to replace.

I finally got some information from the previous owner on when the fluids were done and they are due. We are also going to do the fuel filter with whatever the best is he can find locally.

The tricky item may be the tranny filter. I have the 96 and it seems that the filter is not readily available locally so I may need to order that off the internet. Do people feel replacing this filter is critical? Looking back at old posts seems to imply, yes.

I also ordered a small tranny cooler. I went with a small one for a few reasons. I have a 1996 which should run cooler, have better flow and have little risk of the radiator cooler clogging. Since I am not worried about blockage of flow, I can feel comfortable putting the cooler in series. Still, any additional item, in series, will cause some additional resistance to flow. Pressure will probably increase a little but not enough to make up for the extra resistance. Putting a high capacity, high resistance, cooler in series will cause a measurable decrease in flow rate. That will negate some of the benefits of the additional cooler. Also, since my tranny is one of the newer designs, I shouldn't really need a lot of extra cooling capacity. And I am also switching to Redline synthetic ATF which has a higher temperature tolerance than dino ATF and is ester based which means it will help aid heat extraction. Finally, another benefit of a smaller cooler is that it will introduce less air flow restriction to the radiator, assuming I install it between the condenser and the radiator. Less air flow restriction will mean less impact on engine cooling. Together with less ATF fluid flow resistance, you have the benefits of a smaller cooler. So long as the added cooling capacity for the tranny fluid is sufficient, there shouldn't be an issue. One question I haven't found a good answer to is where should the cooler be placed if mounted between the condenser and the radiator? High or low? Passenger side or driver side? I would think we would want to avoid sending the heat back into the tranny by dumping hot air back onto the areas where the tranny fluid is flowing.

[kwren]

Originally Posted by Huskymaniac

I have been unable to determine which O2 sensor had been replaced previously. I cleared the code a couple of days ago and it hasn't come back yet. Bases on the car wash coincidence, I am wondering if I should just clean the contacts on the sensor and see what happens. Could have been just a fluke or a dirty connector.

The only thing that makes any sense at this point is to simply flip a coin!
Keith

[Huskymaniac]

How long before the ECU re-learns what to do with a new O2 sensor?

[Huskymaniac]

I thought this thread would be "interesting" to update for a couple of reasons.

First, this particular code has never returned since replacing this particular O2 sensor with a new Bosch sensor. Also, the third O2 sensor has not thrown a code since cleaning the contacts.

Second, it is just about a year since I replaced the temperature sender for the temp gauge. After replacing it with an OEM sender from Subaru, the temp gauge has operated normally for a year. The pictures posted are from the recent heat wave. I drove the car for over 20 minutes in 104F heat. The gauge never moved. So CLEARLY, the temp sender was the reason for the LOW gauge readings.




A recent thread about wheel bearings and rear differentials reminded me of a few things. The man who goes by dcarrb is uncanny in his ability to diagnose the REAL problem, svxfiles is a wealth of information, people who say "mine did the same exact thing" can't always be trusted because SOME people rush to make such statements without taking the time to make sure it is really EXACTLY the same, statements like "It's not just a river in Egypt" doesn't help guide people down a rational path and Trevor was a voice of reason.