troubleshooting P2171 intermittent
 

G'day all,

New member from Australia trying to get info on how to diagnose an intermittent P2171 error code (every 2 or 3 hours) determined via a cheap generic ELM327-style OBD2 scanner in a R56 Cooper S with about 65,000 miles on it that's running quite smoothly otherwise.

Looking at online sources that code seems to refer to either System Too Lean Bank 1, or, Exhaust Pressure Regulator Vent Solenoid Control Circuit High, which I would have thought is more likely relevant to a diesel motor.

At any rate, I can't find any further information about it and I'm wondering if anyone has come across this problem. Also, would I get better diagnostics with a dedicated scanner and what's recommend bang4buck-wise.

Any shared experience would be very welcome (because intermittent issues are a bugger).

Onya, cheers

I'm working off of general knowledge, not specific to your R56 but here goes; first, what year is your car? I'm guessing that you have a turbo, and not the supercharger, since the code could be referring to an Exhaust Pressure Regulator Vent Solenoid. That makes more sense to me if you have a turbocharger since I'm not aware of the need for a Vent Solenoid on a supercharged engine. But please keep in mind that's just my guess!

The "System Too Lean Bank 1" would most likely be the result of an Oxygen Sensor telling the computer that there is too much oxygen left in the exhaust gas, and to make the fuel/air mixture richer. It could be a bad oxygen sensor, but when it says "Bank 1" I'm used to seeing this type of code on a V6 or V8 engine, where you have 2 separate banks of cylinders. I'm not yet familiar enough with the MINI's to know, but aren't they all 4 cylinder inlines? If so, IIRC you'll have two oxygen sensors, one before the catalytic converter and one after. But it's the same bank, although it's possible they just refer to it as "Bank 1".

I should mention that I'm here in the US, and emission systems in Australia may be configured differently.

An intermittent problem like this suggests to me that it may be an electrical problem. Sometimes just separating electrical connectors and putting them back together will clear things up. Hopefully my ramblings may point you in the right direction.

For an OBD II scanner, I use an app I got from www.obd-2.com on an old Toughbook laptop with the Tri-Can cable I purchase from the same source. It's not real user friendly, you HAVE to know what you're doing, but it will talk to all the modules in a car or truck, not just the Powertrain Control Module. I've used it for troubleshooting SRS (airbag system) and been able to get codes from the Body Control Module. It will also read the U codes for the vehicle's network, and IIRC I think I once used it for the ABS system in my wife's minivan.

You can't make any program changes with it, it's all Read Only. The only change it will make is to reset the Service Engine Soon light.

I'd start by nailing down for sure what the P2171 code means for sure in your R56. What year is your Mini? I love a good logic problem!

Many thanks mate,

Great overview and you raise some interesting points.

First, the car is 2010 I reckon, so turbocharged as you suggest. Direct injection was introduced in the R56 cars in about '07 I think.

Bank 1 just refers to whichever bank has the no.1 cylinder. Bank 1 lean is just the generic descriptor for that code, however, the mini-specific sites give p2171 as "exhaust pressure regulator vent solenoid control circuit high".

Trouble is the only sites that I can find that mention "exhaust pressure regulator vent solenoid" relate to diesel motors, and I can't find any images or schematics. And there's not much mention at all of the p2171 code in general.

I wonder if the exhaust pressure regulator here is the diverter valve, which i guess is the blow off valve or wastegate equivalent? It does have a solenoid attached but Google search with p2171 reveals nothing either.

I'll check the connection and report back.

The other issue with these GDI motors is deposits on the intake valves so could that produce a lean burn?

Thanks again

One of the manuals I ordered for my daughter's MINI arrived yesterday, but only goes up to 2006. It didn't list code P2171, of course. :/

I'd suggest putting a thread in the 2nd Gen MINI forums below, hopefully someone will have a Bentley Service Manual and would be willing to look this code up for you. I'm not finding anything specific on the 'net either.

I can see a lean burn condition if there's carbon build-up interfering with a valve closing completely, but if such is the case I'd think it would idle rough. If it runs smooth there may be some carbon but not enough IMHO to cause the problem you're seeing.

Going back to the possible definition "Exhaust Pressure Regulator Vent Solenoid Control Circuit High"; this leads me to believe that there is some sort of sensor attached to your wastegate telling the ECM the position, or some sort of status, of what the wastegate is doing.

In English, an example would be that while driving the car at low speed through town and not under boost that the ECM would be telling the wastegate to remain closed. So the ECM is sending a signal to leave the wastegate closed, but is monitoring what the 'gate is doing through a feedback signal, from say a potentiometer. The ECM sets this code when the wastegate is supposed to be closed, but sees that (for whatever reason) that the 'gate ISN'T closed (or otherwise in the condition the ECM thinks it should be).

Since the code is "... Control Circuit High", that leads me to believe that a voltage coming back from a sensor on the wastegate is higher than the ECM finds acceptable. This would likely be the result of the 'gate stuck partially open.

I'm still VERY new to the MINI, and these are guesses based off of experience with other cars. Advice on the internet, you get what you pay for, and all that.

If you don't have a service manual, I'd suggest getting one written by Bentley Publishers. I've found that they're the gold standard of service manuals, and you should be able to find a used copy on eBay for considerably less than a new one from someplace like Amazon! The Chilton's and Haynes Manuals are ok for the most basic stuff, but if you have to go deep to find a problem I'd say the best bet is the Bentley manual.

Let me know what you find,
Dan

Hi Dan and thanks again,

I thought waste gates and diverter valves were all pretty much the same thing and operated on the intake side to control boost so I was discounting the idea that it was the valve.
However, I Goofled it after reading your insightful commentary and realised my ignorance (hardly unusual) https://www.onallcylinders.com/2017/...he-difference/ so it could well be exhaust side.
I know that the diverter valve/waste gate can be a problem in these so I'll follow that up. Looking at this upgrade( ). Presuming the valve is exhaust side, it seems quite likely that a failing diaphragm or related is the problem, so I'll email GFB here in Oz for a bit of supplementary information as this should be right up their alley.
Thanks for the suggestion regards the Bentley manual. I was trying to find something factory as an eBay download, but there's not much for second-gen Minis and the generic aftermarket manuals don't go deep, as you quite rightly suggest.
It's actually my niece's car that the family bought for her 21st recently so I don't have full-time access to it, and her dad works interstate so will wait for him before doing any significant work, which will eventually include turbo oil-feed pipe, engine mount, valve decarb and catch can.
AFAIK the exhaust pressure vent MIL description is Mini-specific.

Thanks again, you're a legend as they say down here downunder.
Cheers,
Marino

From GFB:

"I haven’t heard of that code before, but given its description I think its unlikely to be an indication of a faulty diverter valve.

The diverter valve is in the compressor side of the turbo and passes air from the compressed side to the pre-compressor side to reduce pressure in the intake. This is all before the engine so a fault here shouldn’t really have any effect on the exhaust back-pressure.

From what I can see it looks like the exhaust pressure regulation is part of the emissions EGR system."

I wrote:
"I'm completely new to the motor and thought the diverter valve could be on the exhaust side of the turbo and regulate pressure by diverting the exhaust rather than venting intake pressure.

Struggling to get any info on the code so I thought you guys might enlighten but I'll keep trying. Besides, it's likely that the diverter will need replacement/upgrade at some point."

GFB:
"No problems! Definitely no harm in asking.

The diverter valve isn’t to regulate pressure as much as it is just to release pressure when there is a pressure differential between the intake pre and post throttle. So when you shut the throttle and the throttle plate closes, the air has nowhere to go anymore and would otherwise go back through the turbo and the intake. The diverter valve creates another path for this air.

What you’re thinking of is a wastegate. This is pressure referenced and bypasses exhaust gas around the turbocharger to limit the boost pressure that the turbo makes. The higher the pressure the more the wastegate opens in an effort to keep you at a pre-set peak boost pressure.

I’d also be surprised if this is what the error code is referring to. Sometimes error codes can have fairly confusing wording but they would usually refer to the wastegate as controlling boost pressure or rather than exhaust back pressure."

When I saw Diverter Valve, I thought “wastegate”. Kind of like what Europe calls the bonnet I know as the hood.🤔

Now I’m REALLY curious, as the only turbo car I had was a 2.2L Chrysler and it had a wastegate - but it makes a lot of sense that you don’t want to over boost the intake side if you’re running hard and then get off the throttle!

Right now I’m trying to ward off a virus or some other crud, and the cold tablets are making it hard to think clearly.🤪

Dan

Edit: In case you haven’t seen it yet, down the forum list under 2nd Gen MINI’s there is a sticky about the N14 engine common problems, and #9 talks about this diverter valve. Hope that points you in the right direction.

Many thanks Dan,

"Curiouser and Curiouser" as Alice said.

I discovered that it's actually two codes appearing independently and intermittently, P2171 and P2177. The last time I was a passenger in the car, P2177 appeared after about 10 minutes and there was an additional P2188 Pending, which I think refers to mixture too rich (2171 is too lean??).

The last two times I cleared the codes, once while the vehicle was moving and once after a short stop, they did not reappear - so suggests cause is dynamic/really variable.

Additionally, I have been running Torque Pro and monitoring long and short term fuel trims as well as intake air, coolant and catalyst temps, throttle position and vacuum/boost as well as O2 sensor values and a couple of other things.

Really great that you can have a tablet with all this sexy info in front of you, but what does it all means and, more importantly, how does it all interrelate with respect to vehicle tune and diagnosis???

However, I did note that short term fuel trim seemed to swing from positive to negative quite a lot, while long term stayed relatively stable around 0, and that idle vacuum was down around 15-16 in/Hg, which I thought was a little low.

So, I figure I need to check vac lines and intake tube for leaks, and EGR valve and intake valve for deposits.

Hope you're in top tune yourself.

Cheers,

Marino

I found the descriptions of codes P2177 and P2188 on the Mini Mania site, but they don’t list P2171. It might be in the Bentley manual.

What follows is a real long shot, but once or twice I have seen codes come up for which there’s no documentation. I suspected this is because the basic ECM hardware covered many different models through the corporate line, and some glitch threw out this code that would have made sense in another model, but not enabled in the software of the car I was working on. (I won’t mention names, but the initials are GM!)

Since BMW makes the Mini, it’s possible the same ECM hardware is used in other BMW’s. Producing a special ECM just for the Mini would be expensive. Like I say, it’s a long shot but if P2171 is a ghost code, that’s the only explanation I can think of.

Just out of curiosity, do you have someone with a Mini of a similar year that you can connect your Torque Pro to, for a comparison? I’d be curious to see what their fuel trims and vacuum readings look like.

Sure looks to me like the short term fuel trims are swinging back and forth, trying to point at the problem.

Does the car run or idle rough?

Just finished my first week in a new job (same company), and I feel like I’ve got smoke rolling out my ears! I put down my tool bag, and picked up a laptop - except they say to keep my tool bag around...

Dan

Hiya Dan,

They list p2171 here: http://haveabreak82.blogspot.com/201...odes-list.html
I must have got the code descriptions wrong: p2171 is System Too Lean OFF Idle and p2177 is Exhaust Pressure Regulator Vent Solenoid Control Circuit Too High (can't even find that gadget - nor could the parts rep at the local BMW dealer for that matter) and p2188 (which was Pending) is System Too Rich AT Idle but last time was the first I can remember seeing that one. If the short term trims are fluctuating, maybe that would explain both rich and lean states!!?

I checked vacuum pressure at idle again last night (realised that it would probably vary if the air con was on so turned it off) and it was a much healthier 20 in/Hg.

Only problem is that the short term fuel trim was not getting picked up by my cheapie OBD2 scanner so maybe it's on the way out. I was thinking of upgrading, anyway, because it was only about $15 but I have no idea which one to get.

We've come out of a hot summer here and I'll try leaving the AC off and see if that might make some difference to the frequency of the error codes. I'll keep you posted.

Congrats on your new job.

Cheers mate

Sorry, other way around should be:

p2171 is Exhaust Pressure Regulator Vent Solenoid Control Circuit Too High and,
p2177 is System Too Lean OFF Idle

Nice find on the MINI trouble codes! Page bookmarked.

The P2171 was the first code to appear, before the others did, correct? (Just making sure I’ve got this in order) I’m wondering if what caused the first code to appear is getting worse and is responsible for the A/F ratio being off at idle and off-idle.

Thinking out loud here, more than anything.

Any ideas on how to justify to my wife that I need another Service Manual for a model of MINI I don’t own?🤔

I’m going to read from the top of this thread, see if something pops out at me.

OK,

So today we used a commercial valve-cleaning spray directed into the sensor port on the back of the intake manifold as per instruction, and then took the R56 for an hour-long freeway drive to get it cooking.

We know the approximate frequency of the MIL/code is around 2-4 hours, so we'll see if the duration increases over the next couple of weeks to test the working hypothesis of soot/carbon build up somewhere in the intake or perhaps exhaust system.

We couldn't get a camera into the intake ports without taking off the intake manifold, so can't directly compare the valve stems pre and post spray, however, the test might give us some interesting information.

Really need a dedicated BMW OBD2 scanner.

No improvement after intake valve cleaning treatment.

you def need one ...i have a decent one for $100 but i think it works on north american minis ...it gives me this live data below on R56:

• Fuel system status
• Calculated LOAD Value
• Engine Coolant Temperature
• Short Term Fuel Trim - Bank 1 / Bank 3
• Long Term Fuel Trim - Bank 1 / Bank 3
• Intake Manifold Absolute Pressure
• Engine RPM
• Vehicle Speed Sensor
• Ignition Timing Advance for #1 Cylinder
• Intake Air Temperature
• Air Flow Rate from Mass Air Flow Sensor
• Absolute Throttle Position
• Bank 1 - Sensor 2
• Time Since Engine Start
• Distance Traveled While MIL is Activated
• Fuel Rail Pressure
• Commanded Evaporative Purge
• Fuel Level Input
• Number of warm-ups since DTCs cleared
• Distance traveled since DTCs cleared
• Barometric Pressure
• Bank 1 - Sensor 1 (wide range O2S)
• Catalyst Temperature Bank 1, Sensor 1
• Control module voltage
• Absolute Load Value
• Fuel/Air Commanded Equivalence Ratio
• Relative Throttle Position
• Ambient air temperature
• Absolute Throttle Position B
• Accelerator Pedal Position D
• Accelerator Pedal Position E
• Commanded Throttle Actuator Control
• Long Term Secondary O2 Sensor Fuel Trim - Bank 1 / Bank 3

you wanna find one that includes short term and long term fuel trim by far one of the most useful data ..if you get one that does not give you fuel trims you will have a hard time diagnosing any fuel air related problems. vacuum leaks etc, air sensors, list goes on lol

Well, I’m back after a couple of rough weeks! Learning this new job is like drinking from a fire hose.

But back to the subject at hand; I looked at the video you posted on 3/24 again, showing the GFB kit being installed in the diverter valve.

Have you pulled this valve apart on yours and inspected it? There could be a tear in the diaphragm causing you this grief, or another thing to check would be a resistance check of the actuator coil.

I’m not sure what voltage the car sends to this module, it could be derived from the PCM and putting battery voltage on it could kill it.

But my next step would be to disassemble this valve, clean and inspect, and check to see if the coil is ok.

If we can find out what voltage this coil is expecting, I’d connect it and make sure the valve is operating, and not leaking when closed.

It wasn’t clear from the video, but I thought I saw only two wires going to the coil. Can you tell on your valve if the electrical connector has just two, or are there more wires?

Dan