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Discussion Starter · #1 ·
Hello fellow Outbackers!

First of all, a massive thank you to all of you heroes contributing to this forum, I've learned so much from you!
I have a 2008 outback 3.0 here in northern Sweden which I bought with the engine light on and the error code P0077 with the idea that it would be a pretty simple problem to solve, how wrong I was!

The guy I bought it off got the car from some estate where it had been standing unused for a year and there is no service history so I have no clue how its been maintained. I know the car did not pass the O2 requirements but the previous owner sorted that somehow if that could be related to the P0077 problem. There is a P0160 code in the history(but not active) and my very basic OBD2 reader cannot test or detect the sensor. I checked all 4 O2 sensors, unfortunately I did not write down the resistance but the sides had the same value and there was a higher resistance reading on the front ones.
My first thought was something has been chewing on the wires but they look ok, a car electrician has also confirmed they work fine and the resistance between the ECU and the solenoid gives me 0,3 Ohms which should be good enough I think. Oil and filter has been changed, the solenoid is changed and works fine with a resistance of 7,6 ohms, I've cleaned the connectors but the code and cel remains.

Do you guys have any ideas on how to solve this issue?

A big thank you in advance and kind greetings from Sweden!
 

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I believe the P0077 code is for an intake valve control solenoid on bank 1 which I believe is on the head with cylinder number one.

These solenoids can become clogged from dirty oil. You can try removing the solenoid and cleaning it with brake clean or contact cleaner and see if it starts to work or not. If no success and the wiring tests OK you will need to replace the solenoid valve.

You could also try swapping the solenoids from either side and see if the problem moves to bank two. If the problem does move to bank two this will confirm the wiring is OK on bank one.

Be very careful not to screw the solenoids in to tight/far as you may crack the head if you do.

Seagrass
 

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Discussion Starter · #3 ·
Seagrass, thank you for your reply!

I'll include a photo of the solenoid to avoid misunderstandings.
I had that idea to switch sides but unfortunately the metal loop holding the solenoid down only works on one side, it wont fit on the LH side, the solenoid I just press down then screw the 10 mm bolt holding it down, I know the pressure switch or oil temp sensor is sensitive with regard to how tight you screw it down but not the solenoid I think, or am I wrong?
Font Engineering Machine Gas Auto part
 

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Discussion Starter · #4 ·
Also to clarify with the risk of being stupid here :) switching sides would be RH to LH and not from the rear to the front since there are 4 solenoids right?
 

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I thought the solenoids could be swapped from one head to the other but it appears that is not correct from what you have found.

By the look if that photo you have already cleaned the solenoid and I am guessing that did not fix the problem.

Seagrass
 
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The P0077 relates to the right side AVLS, or variable valve lift system, which is activated by a duty solenoid. The ECM drives the solenoid with a duty-cycle signal, and monitors the current to ensure it corresponds to the signal.

The duty cycle signal is a DC voltage that rapidly switches between being on and off, with the on versus off time varying. When the duty cycle signal is in it's "on" phase, there will be about 10 V at the ECM terminal (connection going to the solenoid), and when the signal is "off" it will be low.

The P0077, "INTAKE VALVE CONTROL SOLENOID CIRCUIT HIGH (BANK 1)", can be triggered when the voltage remains high when it should be low. This can be caused if there's a short between a wire going to the solenoid and another wire carrying 12 V.

Consequently, this code can be triggered even if there's good continuity in the wiring between the ECM and the solenoid, and if the solenoid is good.

Also, with the wiring disconnected at the ECM and the solenoid, check for a low resistance between each of the wires and ground.

When the engine is warmed up, and idling, and everything connected, when measured with a digital voltmeter one of the two wires at the solenoid should have near zero V to ground, and the other should have 1 - 2 V (the 1 - 2 V corresponds to the low duty cycle signal that would be present at idle).

And, yes, the H6 has four solenoids in total. The variable valve lift system solenoids are at the back of the heads (left and right). (The variable valve timing solenoids, which are similar, are further forward.) In the diagram, VVL solenoids #2 and #19 (yelllow highlight). #7 and #26 are the variable valve timing solenoids (red highlight).

518900
 

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Discussion Starter · #7 ·
The P0077 relates to the right side AVLS, or variable valve lift system, which is activated by a duty solenoid. The ECM drives the solenoid with a duty-cycle signal, and monitors the current to ensure it corresponds to the signal.

The duty cycle signal is a DC voltage that rapidly switches between being on and off, with the on versus off time varying. When the duty cycle signal is in it's "on" phase, there will be about 10 V at the ECM terminal (connection going to the solenoid), and when the signal is "off" it will be low.

The P0077, "INTAKE VALVE CONTROL SOLENOID CIRCUIT HIGH (BANK 1)", can be triggered when the voltage remains high when it should be low. This can be caused if there's a short between a wire going to the solenoid and another wire carrying 12 V.

Consequently, this code can be triggered even if there's good continuity in the wiring between the ECM and the solenoid, and if the solenoid is good.

When the engine is warmed up, and idling, and everything connected, when measured with a digital voltmeter one of the two wires at the solenoid should have near zero V to ground, and the other should have 1 - 2 V (the 1 - 2 V corresponds to the low duty cycle signal that would be present at idle).

And, yes, the H6 has four solenoids in total. The variable valve lift system solenoids are at the back of the heads (left and right). (The variable valve timing solenoids, which are similar, are further forward.) In the diagram, VVL solenoids #2 and #19 (yelllow highlight). #7 and #26 are the variable valve timing solenoids (red highlight).

View attachment 518900
plain OM, thank you so much for a great answer, really appreciate it! I will measure the volt at idling and see what comes out and then try to locate a potential short in the wiring, I'm sure google have some help on that! Not sure if there is a fuse to this circuit so I could test it for a short at the fusebox or not?
 

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Discussion Starter · #8 ·
I measured the voltage at the connector to the solenoid at idle to a groundspot on the suspensiontower and both gave around 0,6V, not sure what to make of that.
 

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Odd . . . Was that with everything connected, including the connectors at the ECM and at the solenoid?


Answering your earlier question:

No fuse. Just two wires going from the ECM, through the large bulkhead connector in the engine compartment, and then on to the two-wire connector at the solenoid. See attached diagram

According to the diagram, there's a blue (L) wire at pin 1, and a blue with orange stripe (LOr) wire at pin 2 of the two-wire connector to the right side oil switching solenoid. Normally, pin 1, the blue wire, would have the 1 - 2 V when the engine is idling; pin 2, the blue with orange stripe wire, would always be at or very close to ground (i.e. zero V).

When using a digital multimeter, the voltage at pin 1, is an average of the on and off times of the applied voltage. As the duty cycle % increases (more "on" time) the measured voltage will increase. But the duty cycle will change only when the ECM commands the lift to switch from low to high, and that is when the car is being driven.
 

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Discussion Starter · #10 ·
Odd . . . Was that with everything connected, including the connectors at the ECM and at the solenoid?


Answering your earlier question:

No fuse. Just two wires going from the ECM, through the large bulkhead connector in the engine compartment, and then on to the two-wire connector at the solenoid. See attached diagram

According to the diagram, there's a blue (L) wire at pin 1, and a blue with orange stripe (LOr) wire at pin 2 of the two-wire connector to the right side oil switching solenoid. Normally, pin 1, the blue wire, would have the 1 - 2 V when the engine is idling; pin 2, the blue with orange stripe wire, would always be at or very close to ground (i.e. zero V).

When using a digital multimeter, the voltage at pin 1, is an average of the on and off times of the applied voltage. As the duty cycle % increases (more "on" time) the measured voltage will increase. But the duty cycle will change only when the ECM commands the lift to switch from low to high, and that is when the car is being driven.
Yes that was with everything connected and maybe 15 minutes of ideling. I also did a continuity test on both sides of the bulkhead connector looking for a short while moving the connectors and wires around slightly and it seems to be fine. I also took out the ECU looking for corrosion or visable damages but it looks mint.

Thank you for attaching the diagram, I found it after asking about the fuse!
 

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If the wire at pin 2 (LOr) is, effectively, supposed to be at ground level there should be very little voltage on it. The 0.6 V on that wire (both in fact) seems rather high. (Granted the wire between the solenoid connector and the ECM has resistance, and any current flowing through it would cause a voltage at the solenoid end, but it would mean there's a fairly high current somewhere.)

Check the voltage at the two wires with the engine Off (wait a minute before making measurements to ensure the ECM is in sleep mode).

Also, is there access to allow you make the same voltage measurements (engine off, and then engine on, idling) at the left side VVT solenoid? That would provide a reference.
 

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Discussion Starter · #12 ·
If the wire at pin 2 (LOr) is, effectively, supposed to be at ground level there should be very little voltage on it. The 0.6 V on that wire (both in fact) seems rather high. (Granted the wire between the solenoid connector and the ECM has resistance, and any current flowing through it would cause a voltage at the solenoid end, but it would mean there's a fairly high current somewhere.)

Check the voltage at the two wires with the engine Off (wait a minute before making measurements to ensure the ECM is in sleep mode).

Also, is there access to allow you make the same voltage measurements (engine off, and then engine on, idling) at the left side VVT solenoid? That would provide a reference.
Again, thank you so much for your input! I'll do more measurements tomorrow and share what I find, I should be able to get a probe down the LH side aswell, good thinking!
 

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Discussion Starter · #13 ·
Todays numbers :)
RH 0,65V and 0,7V at warm ideling engine.
LH 1,99 and 0,16V same condition.

Turned off engine, key on "on-position"
RH 0,01V both pins
same on LH, 0,01 on both pins.
 

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Discussion Starter · #14 ·
Took the car for a drive today and took this freeze frame, not sure if it gives any clues or values that seem off

Freeze frame report generated by Torque for Android
=========================================================

Vehicle VIN: JF1BPELUA8G094427
Vehicle Manufacturer: Subaru
Vehicle Calibration ID: D2TB201R
33092304

Freeze frame information:
------------------
Fuel Status = 0 byte
Engine Load = 2,745 %
Engine Coolant Temperature = 93 °C
Fuel Trim Bank 1 Short Term = 7,812 %
Fuel Trim Bank 1 Long Term = −0,781 %
Fuel Trim Bank 2 Short Term = 6,25 %
Fuel Trim Bank 2 Long Term = −3,125 %
Intake Manifold Pressure = 5,221 psi
Engine RPM = 660,5 rpm
Speed (OBD) = 0 km/h
Timing Advance = 17 °
Intake Air Temperature = 35 °C
Mass Air Flow Rate = 4,76 g/s
Throttle Position(Manifold) = 14,118 %
Fuel trim bank 1 sensor 2 = 0 %
Fuel trim bank 2 sensor 2 = 0 %
Run time since engine start = 50 s
EGR Commanded = 0 %
EGR Error = 0 %
Fuel Level (From Engine ECU) = 33,725 %
Barometric pressure (from vehicle) = 14,069 psi
Voltage (Control Module) = 13,672 V
Engine Load(Absolute) = 24,314 %
Commanded Equivalence Ratio(lambda) = 0,997
Relative Throttle Position = 2,745 %
Ambient air temp = 16 °C
Absolute Throttle Position B = 30,98 %
Accelerator PedalPosition D = 12,941 %
Accelerator PedalPosition E = 12,941 %


End of report.
 

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The freeze frame data doesn't stand out, as far as I can tell.

The voltages at the LH side look more normal, i.e., 1.99 V on one wire, and 0.16 on the other (although the 0.16 seems somewhat high, the LH side isn't giving codes.)

With the ignition Off, have you checked the resistance between each of the wires at the RH solenoid and ground (.e., looking back to the ECM, with the solenoid connector disconnected), and compared that to the LH?

I just made a quick measurement at the LH solenoid on my 07 H6. I disconnected the connector at the solenoid and measured at the contacts in the harness connector. The "low" wire measures about 0.2 Ohms to ground (battery negative post), and the "high" wire is around 1.5 megOhms to ground. (The low wire resistance to ground could vary in different cars depending on the length and connectors along the way. The high wire measurement is taking into account the control circuitry in the ECM, and could also vary with different ECMs. but thought having this as a reference might be helpful.)

The last two RH voltage readings are almost the same. (Both were around 0.6 the previous time.) So little or no current flow through the RH solenoid. That means the "low" side wire voltage is being raised off ground by ~0.7 V. Yet, it should be at ground, or close to it. As the code suggests, a short to a power source that impressing voltage on the wire, or, a fault in the ECM, are possibilities.
 

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Discussion Starter · #16 ·
The freeze frame data doesn't stand out, as far as I can tell.

The voltages at the LH side look more normal, i.e., 1.99 V on one wire, and 0.16 on the other (although the 0.16 seems somewhat high, the LH side isn't giving codes.)

With the ignition Off, have you checked the resistance between each of the wires at the RH solenoid and ground (.e., looking back to the ECM, with the solenoid connector disconnected), and compared that to the LH?

I just made a quick measurement at the LH solenoid on my 07 H6. I disconnected the connector at the solenoid and measured at the contacts in the harness connector. The "low" wire measures about 0.2 Ohms to ground (battery negative post), and the "high" wire is around 1.5 megOhms to ground. (The low wire resistance to ground could vary in different cars depending on the length and connectors along the way. The high wire measurement is taking into account the control circuitry in the ECM, and could also vary with different ECMs. but thought having this as a reference might be helpful.)

The last two RH voltage readings are almost the same. (Both were around 0.6 the previous time.) So little or no current flow through the RH solenoid. That means the "low" side wire voltage is being raised off ground by ~0.7 V. Yet, it should be at ground, or close to it. As the code suggests, a short to a power source that impressing voltage on the wire, or, a fault in the ECM, are possibilities.
Thanks for taking the time and bringing in references from your own car, very appreciated! I will measure resistance between wires and ground and compare it between the solenoids, I've done it before but I don't remember the numbers and don't think it stood out but I might be wrong. I've also been thinking it could be a faulty ECM but after being in contact with a few different ECM troubleshooters/technicians plus a authorized subaru shop I dropped that thought since they all said it is so unlikely it would just mess up this particular thing since everything else seems fine systemwise.
 

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Discussion Starter · #17 ·
I could only get reading on certain settings, its a borrowed multimeter and im not too familiar with the settings:

On "20M ohm" setting I read
RH: 0,48 and 0,00
LH: 0,48 and 0,00

On "20K ohm"
RH : 10,76 and 0,26
LH: 10,68 and 0,00

With one probe on the ground side of the battery I also tested continuity and got a signal on LH 2nd wire but nothing on the RH side.
 

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On "20K ohm"
RH : 10,76 and 0,26
The 0,26 could be a/the problem.

Let's confirm the measuring method. The RH solenoid connector is off; all the other connectors for the solenoid wiring to the ECM are attached. Measuring Resistance, with the negative (usually black) meter lead to a good ground (ideally the battery negative post) and the positive (red) lead to the contact in the wiring harness solenoid connector for the blue-with-orange-stripe wire. Is this correct?

If it is, then the reading of 0.26 on the 20K ohm range is indicating 260 Ohms to ground. That's far too high for what should be a fraction of an Ohm. To verify, measure the resistance of that same wire (the 0.26), to ground again, but using a lower resistance range.) Depending on the meter, there could be a 2K range, a 1K range, a 200 Ohm range. ) On a 2K range, the meter would read 0,260K ohms, or perhaps 260 Ohms. (What is the make and model of the meter? I can probably find information about it on-line and advise accordingly.)

If the 260 Ohms is confirmed, then that's probably the fault -- the wiring connection from the solenoid connector to the ECM (or inside the ECM) isn't good.

But let's confirm the method and the measurement . . . (and again, compare the reading on the lower ranges with the same at the LH connector.
 

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Discussion Starter · #19 ·
The 0,26 could be a/the problem.

Let's confirm the measuring method. The RH solenoid connector is off; all the other connectors for the solenoid wiring to the ECM are attached. Measuring Resistance, with the negative (usually black) meter lead to a good ground (ideally the battery negative post) and the positive (red) lead to the contact in the wiring harness solenoid connector for the blue-with-orange-stripe wire. Is this correct?

If it is, then the reading of 0.26 on the 20K ohm range is indicating 260 Ohms to ground. That's far too high for what should be a fraction of an Ohm. To verify, measure the resistance of that same wire (the 0.26), to ground again, but using a lower resistance range.) Depending on the meter, there could be a 2K range, a 1K range, a 200 Ohm range. ) On a 2K range, the meter would read 0,260K ohms, or perhaps 260 Ohms. (What is the make and model of the meter? I can probably find information about it on-line and advise accordingly.)

If the 260 Ohms is confirmed, then that's probably the fault -- the wiring connection from the solenoid connector to the ECM (or inside the ECM) isn't good.

But let's confirm the method and the measurement . . . (and again, compare the reading on the lower ranges with the same at the LH connector.
Attached is the multimeter on 2k setting, everything connected except the connector to RH solenoid, blue/orange wire. Black wire of multimeter to negative side of battery. Key off, engine off.
 

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