P0420 Diagnosis - Page 160 - Subaru Outback - Subaru Outback Forums
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post #1591 of 1746 (permalink) Old 04-09-2019, 05:54 PM Thread Starter
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@samochitwa Add AF correction in to the logs, please.



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post #1592 of 1746 (permalink) Old 04-09-2019, 08:06 PM
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My elevation is 1255m and the air pressure measurement obtained was from a weather station at 1084m. If you do the math, that's only around 0.3 psi difference. I dont think my elevation is that significant to the problem.

Heres the logs. Sorry for all this BS and thanks for the help.

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post #1593 of 1746 (permalink) Old 04-10-2019, 07:43 AM Thread Starter
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Originally Posted by samochitwa View Post
My elevation is 1255m and the air pressure measurement obtained was from a weather station at 1084m. If you do the math, that's only around 0.3 psi difference. I dont think my elevation is that significant to the problem.

Heres the logs. Sorry for all this BS and thanks for the help.
Is the car an auto or manual?
What octane or type of gasoline are you using?

You need to find the cause of the knock correction. The catalytic converter seems to be working but is being overloaded by the added fuel when the ECM is correcting for knock. It's either false or you have something going on that is causing a misfire or detonation. The AF sensor looks to be working and regardless of the atmosphere and MAP reading, the ECM is doing what it's supposed to do.


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post #1594 of 1746 (permalink) Old 04-10-2019, 10:58 AM
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Does that mean that my car could be running slightly lean? From fuel pressure or vacuum leaks? I can check those this weekend if you think it'll help. The spark plugs could be due, but the problems that the P0107 have given me have been around for 3 years (worse in the summer). The car just sometimes feels sluggish, runs rich, bucks around, and stalls at lights.

The car is Automatic. I use 87 octane, and have used 89 (midgrade before) and had the same issues. Ill try again and doing another log

Ill run some Seafoam through the manifold and check the spark plug condition too I guess.

Edit: My car may ping. I dont exactly know what that sounds like but my engine is noisy. Nothing like knocking, but it sounds like multiple exhaust hisses or lifter ticks.

I'm kinda losing hope at this point. And still super confused as to why this has just shown up after not seeing issues for 7 months.
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post #1595 of 1746 (permalink) Old 04-11-2019, 08:30 AM Thread Starter
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Quote:
Originally Posted by samochitwa View Post
Does that mean that my car could be running slightly lean? From fuel pressure or vacuum leaks? I can check those this weekend if you think it'll help. The spark plugs could be due, but the problems that the P0107 have given me have been around for 3 years (worse in the summer). The car just sometimes feels sluggish, runs rich, bucks around, and stalls at lights.

The car is Automatic. I use 87 octane, and have used 89 (midgrade before) and had the same issues. Ill try again and doing another log

Ill run some Seafoam through the manifold and check the spark plug condition too I guess.

Edit: My car may ping. I dont exactly know what that sounds like but my engine is noisy. Nothing like knocking, but it sounds like multiple exhaust hisses or lifter ticks.

I'm kinda losing hope at this point. And still super confused as to why this has just shown up after not seeing issues for 7 months.
Checking for vacuum leaks is all good. But before I can say it's rich, I need to see AF Correction. If your exhaust smells like it's running rich, then it may be, or there's an issue with the exhaust. It could be running too lean from a restriction in the fuel system or weak pump, so that's always something to check. If it's been a while since you replaced the fuel filter, it needs it anyway.

I also thought of the air temp sensor portion of the MAP. If your data list supports it, add that in. The ECM sees pressure and temp from the MAP so it will be split data to the ECM.

I couldn't say what the ticking noise is. It could be detonation, but the data isn't showing a knock until load increases. Ticking could come from the fuel damper, injectors, the purge valve, or any other electrical part on the car. It could also be valve noise or a timing pulley. I'd have to hear it which means you taking video and posting it somewhere we can access it.


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post #1596 of 1746 (permalink) Old 04-11-2019, 11:26 AM
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Ill do some of that over the weekend. AF Correction should be in the last logs that I sent. Have a good one!
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post #1597 of 1746 (permalink) Old 04-11-2019, 11:48 AM Thread Starter
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Ill do some of that over the weekend. AF Correction should be in the last logs that I sent. Have a good one!
Yeah, I posted before looking at the log.

Here it is. The fuel goes lean, starts knocking, ECM adds to balance. See pic. It's under load only, so definitely check fuel delivery.
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post #1598 of 1746 (permalink) Old 04-14-2019, 04:55 PM
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Quote:
Originally Posted by samochitwa View Post
Ill do some of that over the weekend. AF Correction should be in the last logs that I sent. Have a good one!
Yeah, I posted before looking at the log.

Here it is. The fuel goes lean, starts knocking, ECM adds to balance. See pic. It's under load only, so definitely check fuel delivery.
Fuel Pressure is completely fine. FPR checks out. Injectors seem okay. What the heck?

I’ve been getting a flashing AT OIL TEMP light Code 45 since this started. Intake manifold pressure signal (Non-turbo model) - Detects open or shorted input signal circuit on a wire from the ECU to the TCM. The diagnosis consists, primarily, of testing that one wire circuit to see if it's open, shorted or has a bad connection.

I ran through the diagnostic tests and didnt find any issues. I believe the connections are fine and that its a faulty TCU. Replacement of the TCU shouldnt fix the problem, but Im going to give it a go. I will slow down on hyjacking this thread with my TCU issues, and maybe start my own.
Thank you for all your help people, especially you cardoc!
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post #1599 of 1746 (permalink) Old 04-15-2019, 07:59 AM Thread Starter
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Originally Posted by samochitwa View Post
Fuel Pressure is completely fine. FPR checks out. Injectors seem okay. What the heck?

I’ve been getting a flashing AT OIL TEMP light Code 45 since this started. Intake manifold pressure signal (Non-turbo model) - Detects open or shorted input signal circuit on a wire from the ECU to the TCM. The diagnosis consists, primarily, of testing that one wire circuit to see if it's open, shorted or has a bad connection.

I ran through the diagnostic tests and didnt find any issues. I believe the connections are fine and that its a faulty TCU. Replacement of the TCU shouldnt fix the problem, but Im going to give it a go. I will slow down on hyjacking this thread with my TCU issues, and maybe start my own.
Thank you for all your help people, especially you cardoc!
So there's more than just checking a single circuit. There is the most important - Grounds. The modules ground to the body via the harness to several points in the cab and under the hood. I recommend you visit every ground under the hood and check for rust, corrossion, tightness. Replace any ground lug or wire that you find bad. There are ground straps that run from the heads to the body, on top of the intake, by the ABS module, on the firewall, and the transmission. There are several grounds under the dashboard behind the foot panels on the left and right. There are grounds under the center console. These last two areas should be relatively trouble free unless there has been water or other liquid intrusion, high humidity or someone working on the car in these areas.

The battery also has to be putting out ample amperes to supply the whole car. On yours, 550 amp output from a cold battery is good. Anything less is pushing it. If you have more than a 75 amp loss between the battery and engine and alternator, then you have bad cabling.

Your ECM and TCM have reported MAP errors. Something could be causing slow feedback (electricity) to the computers and that is what's making it sporadic in nature. This could also be the cause of the knock and fuel correction leading to the P0420.

You're not hijacking a thread. I started this thread for just this reason. Dealerships and some independents don't find the real source of a problem and only cover it up, or try to cover it up, in shortcut diags. "Get the money and move to the next one." And this usually involves multiple part replacement that does nothing or eventually leads them to the real issue by "accident" as they guess their way through it.

The downside to this thread is time. Don't be in a hurry.


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post #1600 of 1746 (permalink) Old 04-15-2019, 06:36 PM
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Originally Posted by cardoc View Post

So there's more than just checking a single circuit. There is the most important - Grounds. The modules ground to the body via the harness to several points in the cab and under the hood. I recommend you visit every ground under the hood and check for rust, corrossion, tightness. Replace any ground lug or wire that you find bad. There are ground straps that run from the heads to the body, on top of the intake, by the ABS module, on the firewall, and the transmission. There are several grounds under the dashboard behind the foot panels on the left and right. There are grounds under the center console. These last two areas should be relatively trouble free unless there has been water or other liquid intrusion, high humidity or someone working on the car in these areas.

The battery also has to be putting out ample amperes to supply the whole car. On yours, 550 amp output from a cold battery is good. Anything less is pushing it. If you have more than a 75 amp loss between the battery and engine and alternator, then you have bad cabling.

Your ECM and TCM have reported MAP errors. Something could be causing slow feedback (electricity) to the computers and that is what's making it sporadic in nature. This could also be the cause of the knock and fuel correction leading to the P0420.

You're not hijacking a thread. I started this thread for just this reason. Dealerships and some independents don't find the real source of a problem and only cover it up, or try to cover it up, in shortcut diags. "Get the money and move to the next one." And this usually involves multiple part replacement that does nothing or eventually leads them to the real issue by "accident" as they guess their way through it.

The downside to this thread is time. Don't be in a hurry.
Thanks Cardoc. I didnt want to hog this space. Well I did the full P0107 diagnostic from the FSM today and found no faults. The ending options were that there is poor connection along the harness or the sensor is faulty. After not wanting to fart around with either, I replaced the TCU to see if it would change anything.

HERES THE FUN PART. Remember how my MAP values was reading 85kpa (12.3psi) while the vehicle was off? After plugging in the new TCU, I plugged everything back in (battery, map, and ECU) and that value was at 101kpa (14.6psi), the current atmospheric conditions here!!!!

I took the car around the neighbourhood. Turned it off, and the number was back to 85kpa.

Just my luck 😉 Ill check the grounds and test the battery/alternator tonight before the hockey game comes on! Go Flames Go

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