Subaru Outback Forums banner

1 - 20 of 38 Posts

·
Registered
2005 Outback 2.5i - 5 speed - 191K
Joined
·
276 Posts
Discussion Starter #1
I have hade a code P0420 since I got my 2005 2.5i last summer (2017). Car drives great. I need to tackle this since inspection is coming soon. I've read all the posts I can find. Lots of IF's about the various causes. My issue is there are no solid sources identifying what the OBD II is reading and whichg vehicles have which parts. Mine is NON-CA basic 2.5i with the dual cats just before the resonator. I see TWO sensors. One before and one after the cat closest to the engine.

For the moment I used OBD TORQUE for my diagnostics. It works great on my cell with a OBD II Bluetooth reader attached to the car.

What am I looking for. I believe the sensor BEFORE the cat is the Fuel Trim and the sensor AFTER the cat is the actual O2 Sensor.

On my OBD reader the Fuel Trim reads a consistent 3.1% for LONG TERM FUEL Trim when fully warmed up and 4.7 when NOT fully warmed.

(NOTE: Now the Long Term Fuel Trim reads 4.7 consistent with the car full warm)
(NOTE II: Now the Long Term Fuel Trim is at 6.6 and Short Term Fuel Trim is .08 but drops to 0.0 every so often)

It reads 0.8% SHORT TERM FUEL TRIM.

Since there is only one other sensor (the rear sensor) I am confused what it is called within the diagnostic app. The TORQUE app has four O2 sensor readouts.

O2 Sensor1 Equivalence Ratio
O2 Sensor1 Equivalence Ratio (alternate)
O2 Sensor1 wide-range Voltage
O2 Volts Bank 1 Sensor 2

Which of these is the critical reading? I ran 3 of them (excluded the Eq ratio alternate).

Equivalence Ratio is pretty much FLAT LINE at 1

Wide Range Voltage is steady between 2.76 - 2.79

O2 Volts Bank 1 Sensor 2 is ALL OVER THE PLACE. 0.2 -.0.9 volts

I attached sequential screen shots for what the graphs show.


Any help with what I'm looking at is appreciated.

Any help standardizing the terms used and parts involved is appreciated.

I know there are a plethora of causes for this specific code. Im just trying to get a handle on how to read the sensor outputs.
 

Attachments

·
On the Super Mod Squad
02 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
Joined
·
26,212 Posts
how about oil and coolant getting into it::frown2:

http://www.subaruoutback.org/forums/109-gen-3-2005-2009/479202-need-help-space-aliens-steeling-my-oil-coolant-new-issue.html

_____

on torque pro: clear the p0420 code,
and then watch the emissions readiness screen. when you get all of them but one to light up you should be able to pass.
(depends on state, but I live in NY, and can have 1 not ready on a 2002 following the federal guidleines listed on the NY state dmv site.

...so check your PA regulations right on the state's own .gov site ).

when I clear my codes sometimes the emissions readiness comes right back up within 30 miles. on all those sensors. and then even with a light that can pop back on soon after, I can get a inspection before it happens.
 

·
Registered
2005 Outback 2.5i - 5 speed - 191K
Joined
·
276 Posts
Discussion Starter #3
I am sure I can clear codes and get it to pass....

I am actually trying to understand what the readings show so I can FIX the problem.

I am not seeking someone to tell me what is wrong, I would rather figure that out on my own. I just need someone to tell me what sensor reading is the one I need to look at and what that sensor should be reading.

What is considered the "Best" OBD software for a laptop. I want to get something that can log a much longer session when taking readings.
 

·
Registered
Lawn ornament XT
Joined
·
14,366 Posts
OK I'm not familiar with all of those...

But you shouldn't be seeing any major variation in the rear sensor after warm-up. (B1S2)

You should be seeing that kind of variation in B1S1, because the ECU uses a "fishtail" logic to seek the correct burn ratio, and the computer makes corrections based on how far it overshoots each side of the target value on each swing.

Ideally the front sensor always shows a sinewave straddling the target, and the rear sensor shows a flat line indicating that it was able to burn off everything left over in the pipes.

Here they are plotted together using a classic scope. You can probably get these same measurements from torque but I'm not the guy to tell you how.

 

·
Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
Joined
·
16,120 Posts
What is considered the "Best" OBD software for a laptop. I want to get something that can log a much longer session when taking readings.
You really can't go wrong with Romraider and a cheap vagcom cable. Having a connected laptop all the time while logging some may consider cumbersome. I'm a single guy who never has a occupied passenger seat, so I don't mind the cable. Having a fancy BT app that doesn't get you the information you need is worse.
 

·
Registered
Lawn ornament XT
Joined
·
14,366 Posts
What is considered the "Best" OBD software for a laptop. I want to get something that can log a much longer session when taking readings.
Combination of RomRaider and FreeSSM with either a cheap VAGCOM cable or a tactrix interface.
 

·
On the Super Mod Squad
02 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
Joined
·
26,212 Posts
You really cant go wrong with Romraider and a cheap vagcom cable. having a connected laptop all the time while logging some may consider cumbersome. But, having a fancy BT app that doesn't get you the information you need is worse.
I guess free rom-raider on a $10 VAG cable, could also tell which cylinders are leaking.
 

·
Registered
05 Outback, 15 WRX
Joined
·
46 Posts
Correct, your rear O2 (O2 Bank 1 Sensor 2) Should not be fluctuating like that once warmed up. I believe it should be steady around 0.6 V

O2 Sensor1 Equivalence Ratio: Should be steady around 1. Equivalent to 14.7. That ratio
O2 Sensor1 Equivalence Ratio (alternate): related to above
O2 Sensor1 wide-range Voltage: Same sensor voltage. Someone can chime in
O2 Volts Bank 1 Sensor 2: This should be lower than Sensor 1. Should be steady around 0.6?

I wish you luck as I'm still trying to figure out my CA 2005 outback.
 

·
Registered
2005 Outback 2.5i - 5 speed - 191K
Joined
·
276 Posts
Discussion Starter #9
Is is a consensus the UPSTREAM sensor should be a sine wave pattern and the down stream should be a flatlane if working properly?

Will the engine run if I disconnect one or both sensors?
 

·
On the Super Mod Squad
02 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
Joined
·
26,212 Posts
Correct, your rear O2 (O2 Bank 1 Sensor 2) Should not be fluctuating like that once warmed up. I believe it should be steady around 0.6 V

O2 Sensor1 Equivalence Ratio: Should be steady around 1. Equivalent to 14.7. That ratio
O2 Sensor1 Equivalence Ratio (alternate): related to above
O2 Sensor1 wide-range Voltage: Same sensor voltage. Someone can chime in
O2 Volts Bank 1 Sensor 2: This should be lower than Sensor 1. Should be steady around 0.6?

I wish you luck as I'm still trying to figure out my CA 2005 outback.
with california spec 2005, you might be able to get a free cat converter from subaru on that particular weird year.
(read of others here being able to do that). kind of a last expensive resort for all others after trying everything cheaper.

o2 sensors just get worn overtime also. ($50-120 for a new denso, depending upon exact type).

some people are known to put a spacer on the rear one to stop p0420 codes. (such maybe looked for in states with government inspectors actually looking under the car for such things, ...vs. plain old garages plugging into a state computer).
 

·
Registered
2005 Outback 2.5i - 5 speed - 191K
Joined
·
276 Posts
Discussion Starter #11
Now the Long Term Fuel Trim is at 8.6%.

The Fuel trim sensor is the sensor BEFORE the cat???
 

·
Registered
Lawn ornament XT
Joined
·
14,366 Posts
Is is a consensus the UPSTREAM sensor should be a sine wave pattern and the down stream should be a flatlane if working properly?

Will the engine run if I disconnect one or both sensors?
The engine will run without the sensors connected, but you will gather extra ECU codes with the loss of connection. And the car won't run well- it's just going off a preprogrammed failsafe map rather than attempting to correct for actual conditions.

Going back to your first post- fuel trims are not sensor readings. They are registers calculated by the ECU. They exist to let you see what the ECU has been doing. A positive fuel trim indicates that the ECU has been adding fuel in reaction to *something*. If the ECU needs to do that for long enough, it becomes a long-term trim. The trims become a cheat-sheet to let the ECU tune itself to actual conditions. Sometimes you can spot weird trends there and trace them back to root causes.

Essentially a fuel trim is the ECU's way of remembering "what worked last time" in the scope of serially solving the problem, "How much fuel??"
 

·
Registered
2005 Outback 2.5i - 5 speed - 191K
Joined
·
276 Posts
Discussion Starter #13
Is is a consensus the UPSTREAM sensor should be a sine wave pattern and the down stream should be a flatlane if working properly?

Will the engine run if I disconnect one or both sensors?
The engine will run without the sensors connected, but you will gather extra ECU codes with the loss of connection. And the car won't run well- it's just going off a preprogrammed failsafe map rather than attempting to correct for actual conditions.

Going back to your first post- fuel trims are not sensor readings. They are registers calculated by the ECU. They exist to let you see what the ECU has been doing. A positive fuel trim indicates that the ECU has been adding fuel in reaction to *something*. If the ECU needs to do that for long enough, it becomes a long-term trim. The trims become a cheat-sheet to let the ECU tune itself to actual conditions. Sometimes you can spot weird trends there and trace them back to root causes.

Essentially a fuel trim is the ECU's way of remembering "what worked last time" in the scope of serially solving the problem, "How much fuel??"
Do you have any specific information about that spacer you describe? I have read other posts where a owner installed a "bung" that he purchased off eBay. I have been unable to locate any device such as described.
 

·
On the Super Mod Squad
02 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
Joined
·
26,212 Posts
Do you have any specific information about that spacer you describe? I have read other posts where a owner installed a "bung" that he purchased off eBay. I have been unable to locate any device such as described.
mechanics make them. starts out as a steel plug that they know fits and then they drill through it to make a spacer.

edit: something to do on a known good new rear o2 sensor though,...if its just a old turd it might not work.
 

·
Registered
Lawn ornament XT
Joined
·
14,366 Posts
Do you have any specific information about that spacer you describe? I have read other posts where a owner installed a "bung" that he purchased off eBay. I have been unable to locate any device such as described.
I think you confused my post with Eagleeyes.

I've never tried the spacer trick. I understand it works well on the older Subarus, but the 2005 and up use the rear sensor data for more things than the older cars did, so I'm not sure the trick can work as well.
 

·
Registered
2005 18psi supercharged U5 Outback w/207k+ miles
Joined
·
757 Posts
Yes the fuel trims are mostly based off of the pre cat sensor. It is a different sensor which is more accurate. The rear o2 for the most part just monitors, on some cars is makes slight adjustments to fuel trims (I don't think yours is one of them... it is on the 5 o2 sensor vehicles).

I don't think the spacer is going to fix it. You might just end up with a different code like P2096.
I think you want to get the graph going like seen on page 1 and see what the rear o2 is saying.
 

·
Registered
2005 Outback 2.5i - 5 speed - 191K
Joined
·
276 Posts
Discussion Starter #17
Yes the fuel trims are mostly based off of the pre cat sensor. It is a different sensor which is more accurate. The rear o2 for the most part just monitors, on some cars is makes slight adjustments to fuel trims.

I don't think the spacer is going to fix it. You might just end up with a different code like P2096.
I think you want to get the graph going like seen on page 1 and see what the rear o2 is saying.
Using the logic from the video on page 1, my B1S2 is fluctuating which suggests the Cat is degraded however I can't find a reading for B1S1 in Torque. If I had that reading I could see if it was working or if it was the broken sensor.
 

·
Registered
Lawn ornament XT
Joined
·
14,366 Posts
Using the logic from the video on page 1, my B1S2 is fluctuating which suggests the Cat is degraded however I can't find a reading for B1S1 in Torque. If I had that reading I could see if it was working or if it was the broken sensor.
I don't know what Torque would call it, but the same sensor is alternately labeled AFR (air-fuel ratio), lambda, and a couple of other things. Note that the 1st result you find may not be the voltage at the sensor- the reading you find may have been converted into other units so it may not be directly comparable. Either way plotting it against time and post-cat sensor data would be useful.
 

·
Registered
2005 Outback 2.5i - 5 speed - 191K
Joined
·
276 Posts
Discussion Starter #19
I'm pricing aftermarket Cats. I have a hole at the split to the mufflers and need to get a new resonator section. While at it, I'll just use my tax return to get new cats. The ones on the car are obviously originals and are probably really tired.

Is there a generally accepted aftermarket Cat that works? Was looking at Walker products. I'm not coughing up $750-900 for OEM.

Is there a good method to check for exhaust leaks? I can hear exhaust noises a I'm sure there is a leak somewhere, just not sure where.

Ideas??
 

·
Registered
Joined
·
40 Posts
I'm pricing aftermarket Cats. I have a hole at the split to the mufflers and need to get a new resonator section. While at it, I'll just use my tax return to get new cats. The ones on the car are obviously originals and are probably really tired.

Is there a generally accepted aftermarket Cat that works? Was looking at Walker products. I'm not coughing up $750-900 for OEM.

Is there a good method to check for exhaust leaks? I can hear exhaust noises a I'm sure there is a leak somewhere, just not sure where.

Ideas??
I'm trying to figure out, myself, what the deal is with buying a cat for Calif. emissions.
RockAuto has a set of cats that specify being for calif. emissions but that they're still illegal for sale in CA/NY.
Any idea what the deal is? Is it actually to CARB spec or is it just the right dimensions and location?

I'm in the same boat. I've tried the spacer (some use spark plug defoulers) and that didn't work.
Coincidentally I had a split at my exhaust Y to the mufflers and put muffler putty in. Did the trick but am looking to replace the whole system eventually. RockAuto resonator section and mufflers are pretty cheap.

As far as leaking near the back I have the same issues as well, my guess is that with my '05 having 284k on it, the muffler/radiator baffles inside have corroded and there's just pieces floating around rattling.
 
1 - 20 of 38 Posts
Top