P164B Oil Pressure Switch Malfunction

[a4lownslow]

Working on a 2009 A4 2.0T

Car is throwing p164B oil pressure switch malfunction when engine reaches 3500-4000 rpm as well as EPC. No engine noise.

I understand this engine has a two phase variable oil pump. First thing I did was replace blue oil pressure switch, no change. I then hooked up oil pressure gauge and have a good 18-20psi hot idle, but I’ve noticed when revving the engine to 3500-4000 rpm the oil pump never switched over to high side pressure and my reading is stuck at 20-25psi. I then unplugged the oil pressure regulating valve (which should default to high pressure), but still same reading.

At this point I’m assuming the oil pump is faulty. Thoughts?


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[Allowencer]

The top two oil pressure switches around the oil filter only "close" at certain pressures. The lower one closes when there's 10-12 psi and then the other one closes at 30-35 psi (IIRC). They only detect, they do not change or alter oil pressure.

The pressure is controlled by a solenoid valve in the upper oil pan, just below the end of the block, on the front side of the engine, towards the left/driver side. N428 is the valve I'm referring to.

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[a4lownslow]

The top two oil pressure switches around the oil filter only "close" at certain pressures. The lower one closes when there's 10-12 psi and then the other one closes at 30-35 psi (IIRC). They only detect, they do not change or alter oil pressure.

The pressure is controlled by a solenoid valve in the upper oil pan, just below the end of the block, on the front side of the engine, towards the left/driver side. N428 is the valve I'm referring to.

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No. The lower blue switch is the high pressure switch which as I stated was replaced.

I then stated I unplugged the oil pressure regulating valve ( the one you’re referring to as N428). Which did not change pressure. Leading me to believe the pump is bad and not able to change over to high pressure.


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[Allowencer]

Sorry, I may have flipped them (the detection switches).

None the less, the pump doesn't "switch" it's directly driven off of the crank by a chain.

The valve I'm referring to controls pressure. Just because you unplugged it doesn't mean you will get your desired testing result. Did you ohm it? Did you check the wiring to the sensor? Maybe it fails open?

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[a4lownslow]

Sorry, I may have flipped them (the detection switches).

None the less, the pump doesn't "switch" it's directly driven off of the crank by a chain.

The valve I'm referring to controls pressure. Just because you unplugged it doesn't mean you will get your desired testing result. Did you ohm it? Did you check the wiring to the sensor? Maybe it fails open?

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I appreciate you trying but I don’t think you understand fully how the system works. Yes the pump is constantly driven off the chain. It’s a “variable pump” meaning the pressure can be varied using the oil pressure regulating valve which is an electronically controlled solenoid. This solenoid is what varies the output of the pump.. so when it’s electrically disconnected the system should default to high pressure.


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[Allowencer]

Me trying, wow. Guess you don't know who I am

Here's pics. Zero switches or solenoids. Period.

Since I know nothing, read this thread: https://r.tapatalk.com/shareLink/top...ink_source=app


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[a4lownslow]

Me trying, wow. Guess you don't know who I am

Here's pics. Zero switches or solenoids. Period.

Since I know nothing, read this thread: https://r.tapatalk.com/shareLink/top...ink_source=app


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You continue to prove my point.. do you not understand the oil pump high/low pressure is directly controlled by the oil pressure regulating valve, which is the electronic solenoid on the front lower part of engine. Your picture of the oil pump proves nothing


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[Allowencer]

Dude, read post 4. I said the same damn thing

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[Smac770]

Two oil pressure switches. Oil pressure switch F22, blue, is wired to the J519, pin 5 in 32-pin black, via pin 9 in the 17-pin white in the ECM box. Reduced oil pressure switch F378, brown, is wired to the J623. The blue switch is right below the brown in B8.5, it's down near the belt tensioner in B8.0. Both switches are the same, just with different pressure set points. Oil pressure is sufficient to close contact, it does, control module sees a closed circuit to ground. Oil pressure is insufficient to close contact, it does not, control module sees an open circuit. The switches ground to the oil filter stand / accessory bracket; there's only one wire to the switches. The detrigger/trigger range is the same for B8.0 and B8.5, for CAE and CPM. 0.55-0.85 bar for brown; 2.15-2.95 bar for blue.

The oil pump itself is both self-regulating and dual range. SSP 436, pages 22-31, cover the Gen2 system pretty well. The self regulation is a mechanical feedback system, intended to deal with the variable pumping rate as it's hard tied to the engine rpm spread. The dual range switching is controlled by the N428, one of the many devices on fuse 7 of the ECM box. 12v to N428 pin 2, the J623 ECM grounds pin 1 to activate the solenoid. Actuated, the pump is in low pressure range (~1.8 bar). Not actuated, the pump is in high pressure range (~3.5 bar).

The workshop manual defines the test values one should observe. 1.6±0.4 bar at idle; 1.9±0.3 bar at 2000 rpm; 3.5±0.5 bar at 3700 rpm. The switchover point is 3500 rpm, and the activation of the N428 (for low pressure range) can be observed in the J623 measuring values. There's plenty of times below 3500 where the ECM might elect high pressure range (cold start high idle, etc). Even if the solenoid was stuck in low pressure range, your measured pressures aren't on the healthy side of the specs.

It could well be the solenoid is frozen in the actuated position (it'll look and function a lot like the VVT solenoids for the EA113 or EA837). Or you have an internal issue in the pump. Or you have blockage at the pump screen or intake tube screen and the pump cannot flow the necessary volume. Or you have a downstream issue like the balance shafts and the pump could never flow the necessary volume. Getting that lower oil pan off certainly wasn't made easy by VAG, but it could probably have been worse.

[marshallnoise]

Two oil pressure switches. Oil pressure switch F22, blue, is wired to the J519, pin 5 in 32-pin black, via pin 9 in the 17-pin white in the ECM box. Reduced oil pressure switch F378, brown, is wired to the J623. The blue switch is right below the brown in B8.5, it's down near the belt tensioner in B8.0. Both switches are the same, just with different pressure set points. Oil pressure is sufficient to close contact, it does, control module sees a closed circuit to ground. Oil pressure is insufficient to close contact, it does not, control module sees an open circuit. The switches ground to the oil filter stand / accessory bracket; there's only one wire to the switches. The detrigger/trigger range is the same for B8.0 and B8.5, for CAE and CPM. 0.55-0.85 bar for brown; 2.15-2.95 bar for blue.

The oil pump itself is both self-regulating and dual range. SSP 436, pages 22-31, cover the Gen2 system pretty well. The self regulation is a mechanical feedback system, intended to deal with the variable pumping rate as it's hard tied to the engine rpm spread. The dual range switching is controlled by the N428, one of the many devices on fuse 7 of the ECM box. 12v to N428 pin 2, the J623 ECM grounds pin 1 to activate the solenoid. Actuated, the pump is in low pressure range (~1.8 bar). Not actuated, the pump is in high pressure range (~3.5 bar).

The workshop manual defines the test values one should observe. 1.6±0.4 bar at idle; 1.9±0.3 bar at 2000 rpm; 3.5±0.5 bar at 3700 rpm. The switchover point is 3500 rpm, and the activation of the N428 (for low pressure range) can be observed in the J623 measuring values. There's plenty of times below 3500 where the ECM might elect high pressure range (cold start high idle, etc). Even if the solenoid was stuck in low pressure range, your measured pressures aren't on the healthy side of the specs.

It could well be the solenoid is frozen in the actuated position (it'll look and function a lot like the VVT solenoids for the EA113 or EA837). Or you have an internal issue in the pump. Or you have blockage at the pump screen or intake tube screen and the pump cannot flow the necessary volume. Or you have a downstream issue like the balance shafts and the pump could never flow the necessary volume. Getting that lower oil pan off certainly wasn't made easy by VAG, but it could probably have been worse.

Great info here.

As far as removing the oil pan in car, it isn't that awful. Just a couple of bolts that are a little tedious to get. If you can wrench at all, then it will be a straightforward task. I would advice pulling it off one evening, setting out catch pans or whatever and then put it back together the following day after all the residual oil has drained out.

Based on the first post, I would say the oil pump is stuck in the low position and is indeed faulty. Replace with OEM only (new or used, who cares).

[a4lownslow]

New oil pump (Genuine Audi, current rev) made no difference. Basically stuck at 18-22psi hot idle up to 4k rpm. On initial cold start pressure will climb to 60psi and come down after 5 min or so. I’m hesitant to replace balance shafts - I was just in there for timing chain service - and the low oil pressure symptoms don’t seem to line up with failed balance shafts. ie: low pressure at idle. Mine just won’t build pressure.

I find it interesting given these circumstances that it does not throw a red low oil pressure warning to alert of a major problem. I suppose thats because the brown low switch is closed, but the blue high switch stays open, triggering EPC and reduced power once acceleration reaches 3500-4000rpm.

This obviously can’t be good for the engine to be running at 20psi all the time

Not sure what to look at next


Piston rings replaced 25k miles ago per carfax


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[marshallnoise]

New oil pump (Genuine Audi, current rev) made no difference. Basically stuck at 18-22psi hot idle up to 4k rpm. On initial cold start pressure will climb to 60psi and come down after 5 min or so. I’m hesitant to replace balance shafts - I was just in there for timing chain service - and the low oil pressure symptoms don’t seem to line up with failed balance shafts. ie: low pressure at idle. Mine just won’t build pressure.

I find it interesting given these circumstances that it does not throw a red low oil pressure warning to alert of a major problem. I suppose thats because the brown low switch is closed, but the blue high switch stays open, triggering EPC and reduced power once acceleration reaches 3500-4000rpm.

This obviously can’t be good for the engine to be running at 20psi all the time

Not sure what to look at next


Piston rings replaced 25k miles ago per carfax


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That range is perfectly within spec, I believe. The switchover is at 3.5K or so and on my car peaks at 45 psi hot. Low idle on my car is below 10 psi, so I unplugged the N428 valve and it runs 12-15 psi all the time down low and rises to 45 psi over 4K.

Get a gauge on it that you can read while cruising around. Then come back with results. These cars have super low oil pressure, in my opinion, out of the box.

[a4lownslow]

That range is perfectly within spec, I believe. The switchover is at 3.5K or so and on my car peaks at 45 psi hot. Low idle on my car is below 10 psi, so I unplugged the N428 valve and it runs 12-15 psi all the time down low and rises to 45 psi over 4K.

Get a gauge on it that you can read while cruising around. Then come back with results. These cars have super low oil pressure, in my opinion, out of the box.

My readings are not normal, besides at idle.

Idle spec is around 15-18psi. 2k rpm should be 23-33psi. 3700rpm 43-58psi.

I have physical gauge hooked up and driving the car from idle to 5k rpm pressure does not go above 21-22psi. This is with hot engine after running 10 minutes. Idle pressure will drop to around 18psi

[marshallnoise]

My readings are not normal, besides at idle.

Idle spec is around 15-18psi. 2k rpm should be 23-33psi. 3700rpm 43-58psi.

I have physical gauge hooked up and driving the car from idle to 5k rpm pressure does not go above 21-22psi. This is with hot engine after running 10 minutes. Idle pressure will drop to around 18psi

That is new information.

[Theiceman]

Thought this was very interesting for those with low oil pressure issues...

these o rings seem easier to change than balance shafts when troubleshooting low oil pressure.


https://www.audiworld.com/forums/a4-.../#post25912791

[a4lownslow]

Thought this was very interesting for those with low oil pressure issues...

these o rings seem easier to change than balance shafts when troubleshooting low oil pressure.


https://www.audiworld.com/forums/a4-.../#post25912791

Good info on the retaining post. Thanks. Just replaced it with a new part 06J115679E. No change.


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[Smac770]

Yeah, the red oil pressure "turn engine off now" warning is for the reduced oil pressure switch not being active when the engine is running. The yellow "don't go over 4k" is for the oil pressure switch not being active when the ECM is not activating the oil pressure switch valve. There was nothing in the pickup tube or on the pickup screen?

Are you using the same N428 valve as before? There might be something stuck/wrong inside of it keeping the oil pump in low pressure range. Don't know if with it pulled out, if you actuate it with the output test (oil pressure regulation valve) if the toggling can be visually verified. https://www.ebay.com/itm/175828123143 I assume the filter screen on the end is the intake. Deenergized, it's routed to the outer ring of ports (outer as in towards the electrical connector end), energized, it's routed to the inner ring of ports (towards the screened end), based on the SSP diagrams. Should be simple to test with the output test and some lightly compressed air.

Checking that piston under the oil filter is certainly worth a look. That piston is only ~$25.

[a4lownslow]

Yeah, the red oil pressure "turn engine off now" warning is for the reduced oil pressure switch not being active when the engine is running. The yellow "don't go over 4k" is for the oil pressure switch not being active when the ECM is not activating the oil pressure switch valve. There was nothing in the pickup tube or on the pickup screen?

Are you using the same N428 valve as before? There might be something stuck/wrong inside of it keeping the oil pump in low pressure range. Don't know if with it pulled out, if you actuate it with the output test (oil pressure regulation valve) if the toggling can be visually verified. https://www.ebay.com/itm/175828123143 I assume the filter screen on the end is the intake. Deenergized, it's routed to the outer ring of ports (outer as in towards the electrical connector end), energized, it's routed to the inner ring of ports (towards the screened end), based on the SSP diagrams. Should be simple to test with the output test and some lightly compressed air.

Checking that piston under the oil filter is certainly worth a look. That piston is only ~$25.

I have not replaced the n428 valve. I did remove it to visually Inspect and I also connected 12v power and can hear the solenoid clicking. Seems to be fine?

I came across a video on YouTube showing pressure gauge hooked up, and from idle as he revs the car pressure increases to 26-28psi before switching to high pressure. So it seems even if the n428 was defective I should still be able to produce 5-6psi more than what I am in normal low pressure operation.

Just replaced retaining post 06J115679E. No change.


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[Allowencer]

You didn't want to believe what I said above about how the pump operates.

You have a mechanical issue more than likely. Balance shaft(s) bearing issue and/or main/rod bearing(s).

Take off your oil filter, cut it open, look in-between the filter folds for debris. Takes pics for us.

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[a4lownslow]

You didn't want to believe what I said above about how the pump operates.

You have a mechanical issue more than likely. Balance shaft(s) bearing issue and/or main/rod bearing(s).

Take off your oil filter, cut it open, look in-between the filter folds for debris. Takes pics for us.

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It’s not that I didn’t believe it’s the fact that you gave incorrect information multiple times including how the oil pump operates and is controlled.

Based on the information I provided and the response from others after you it was a logical approach to drop the pan and replace the pump.

Nothing you said proved otherwise. If so please elaborate.

What I can say at this point is I do agree there seems to be an internal issue, but you have to keep in mind my symptoms don’t match up with typical low oil pressure issues/wear.

Pretty much every post that’s out there dealing with low oil pressure has to do with low oil pressure at idle and maybe throughout the rpm range with pressure building and responding but on the low side of spec

So how can this engine have internal wear, yet shows no signs of low oil pressure at idle (where it would presumably be most noticeable), but somehow can’t build any pressure off idle??

FYI: there was no metal in the pan or pickup tube.


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[RockJGC]

You didn't want to believe what I said above about how the pump operates.

You have a mechanical issue more than likely. Balance shaft(s) bearing issue and/or main/rod bearing(s).

Take off your oil filter, cut it open, look in-between the filter folds for debris. Takes pics for us.

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I'm a little late to the discussion, but I still wanted to ask this: How would balance shafts issues cause low oil pressure? If the balance shafts are on the downstream side of the oil pressure sensors, then it seems that any obstruction in the balance shafts couldn't cause low oil pressure. I'd even say that it seems much more like for balance shafts issues to cause high oil pressure, or at least increased oil pressure.

[Allowencer]

Listen, what I said was 100% accurate and correct. Hell, you even said the same thing as I did (so you must be misreading what I'm typing).

The pump is static from an RPM perspective; it's directly tied to the crank. We all know this.

There is a relief spring inside the pump which prevents a max (unknown, I don't know the pressure) pressure output. The pressure is controlled by the solenoid above it.

When I build engines, I hook up a starter and wet oil run the crank (no spark plugs). I then manually activate the PWM solenoid to increase pressure. This is how I know if oil co trol and oil pressure is good before I send the engine to the shop who installs them for customers.

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[Smac770]

If you had a scale taped to your hand, press against a wall. You can measure the force your muscle is pushing with. Now press against the air, push as fast and hard as you can. You'll never get a reading anywhere close to when you're pushing against something that can push back. The measurement of fluid pressure is no different.

Another way to think of it, same as measuring the water pressure in your house: https://www.melling.com/wp-content/u...re-vs-flow.pdf

The problem is like in my upstairs, where if I have all the vents full open, the two bedrooms right under the air handler get blasted with air while the two bedrooms on the other end get very little. The system should have been designed with proper flow restriction balancing, or I can just half shut those two vents. Now the air is balanced between the four rooms.

That's the problem with having lacking oil pressure in the engine. You can't be sure the oil is pushing to everywhere in the minimum amount everywhere needs, if there's a "faucet left open" somewhere, like the balance shafts. Now you can't be sure the VVT is getting enough oil flow, since it's much easier for the oil to just flow through the shafts than the engine design intended.

[RockJGC]

If you had a scale taped to your hand, press against a wall. You can measure the force your muscle is pushing with. Now press against the air, push as fast and hard as you can. You'll never get a reading anywhere close to when you're pushing against something that can push back. The measurement of fluid pressure is no different.

Another way to think of it, same as measuring the water pressure in your house: https://www.melling.com/wp-content/u...re-vs-flow.pdf

The problem is like in my upstairs, where if I have all the vents full open, the two bedrooms right under the air handler get blasted with air while the two bedrooms on the other end get very little. The system should have been designed with proper flow restriction balancing, or I can just half shut those two vents. Now the air is balanced between the four rooms.

That's the problem with having lacking oil pressure in the engine. You can't be sure the oil is pushing to everywhere in the minimum amount everywhere needs, if there's a "faucet left open" somewhere, like the balance shafts. Now you can't be sure the VVT is getting enough oil flow, since it's much easier for the oil to just flow through the shafts than the engine design intended.

But how could the balance shafts be less restrictive? I thought we were talking about the balance shafts having more restriction? Or am I not understanding something here?

[Smac770]

If the balance shafts were creating a restriction, back pressure at the sensors would rise. The issue with the balance shafts is about creating too free a flow down that path. Whether the screens, when properly in place, are that much of a restriction, or if it's some issue in the bearings, no idea. Not sure if anyone has done a post-op on them to compare bad pulls vs new ones in those specific regards. But they are certainly one of the more common causes of low oil pressure reading that comes up over time here. Unfortunately, there's no way to know if they are a problem without just replacing them and see if anything changed. Pretty much like the numerous other points on this engine that can impact measured oil pressure.

The general diagram of the EA888 Gen1/Gen2 oil system is posted here: https://www.audiworld.com/forums/a4-.../#post25565712
Notice after the pump sends the oil through the oil filter, there's a basic split between the path up into the head for the VVT, cams, and vacuum pump, and the path into the block for the crank and balance shaft bearings and the spray jets and chain tensioners. So if the path through any of that is "easier than it should be", you'll get reduced pressure at the sensors. And whichever path is taking the excess volume due to the easier flow, now you risk reduced volume to the other path (the head in this case).

What all this thread is about, I can't completely recall. But that's what is issue with the balance shafts and oil pressure on these engines. It's not the oil cause of oil pressure issues, and it's not necessarily a common issue "across the full vehicle inventory". But if it is balance shafts, that's why.