[chapleaurocks]

2018 Lariat. Coming from work and my truck throws a code and the check engine light comes on. The engine goes into low power mode. Put my scanner on it and it said there's a turbo/overboost issue. Not sure if it's the EGR again or if it's my turbo. Which I have had replaced already as well. Going to go talk to dealer and see what they say and can do for me.

 

[Dunrollin]

Hope is isn't something too serious, let us know what you find out.

 

[chapleaurocks]

I will.

 

[jmperlik]

Couple questions to answer to see if we can figure out anything more here:

Vehicle: 2018 Lariat 3.0L V6 PSD

1. Current mileage?
2. Actual ODB code/number thrown? P0234?
3. Status of 18E02 EGR By-Pass valve recall?
4. Status of 20E04 EGR By-Pass valve recall?
5. Are you indicating that your turbo has previously been replaced also?
   • If so, can you provide some background/history behind this previous failure?
   • Was the turbo replaced under warranty?
6. Original owner? Or did you buy used?

No guarantees on diagnosis but we can flesh things out further here.

2018 Model year = your truck was subject to both 18E02 and 20E04 By-Pass valve recalls

=> Hence why I am asking for the recall status for both recalls​

=> If you are unsure, ask your dealer for a VIN-specific OASIS report​

=> OASIS report will contain any-and-all recall work Ford has done on your truck​

I think the only other P0234 we have seen here was Post #56 from @flharrison in the infamous START HERE: Any owners affected by FSA 18E02 (EGR By-pass valve replacement) thread, which was clouded by being at the same time as the 18E02 recalls. If you follow his updates in that thread, I think they found a loose pin in the VGT in the turbo and some form of exhaust leak.

Welcome to the forums = wish your intro could have been on a better note...

 

[chapleaurocks]

Couple questions to answer to see if we can figure out anything more here:

Vehicle: 2018 Lariat 3.0L V6 PSD

1. Current mileage?
2. Actual ODB code/number thrown? P0234?
3. Status of 18E02 EGR By-Pass valve recall?
4. Status of 20E04 EGR By-Pass valve recall?
5. Are you indicating that your turbo has previously been replaced also?
   • If so, can you provide some background/history behind this previous failure?
   • Was the turbo replaced under warranty?
6. Original owner? Or did you buy used?

No guarantees on diagnosis but we can flesh things out further here.

2018 Model year = your truck was subject to both 18E02 and 20E04 By-Pass valve recalls

=> Hence why I am asking for the recall status for both recalls​

=> If you are unsure, ask your dealer for a VIN-specific OASIS report​

=> OASIS report will contain any-and-all recall work Ford has done on your truck​

I think the only other P0234 we have seen here was Post #56 from @flharrison in the infamous START HERE: Any owners affected by FSA 18E02 (EGR By-pass valve replacement) thread, which was clouded by being at the same time as the 18E02 recalls. If you follow his updates in that thread, I think they found a loose pin in the VGT in the turbo and some form of exhaust leak.

Welcome to the forums = wish your intro could have been on a better note...

43,0000 miles. Yes it was P0234. I believe all recalls were done. Original owner. Yes turbo replaced already after EGR was fixed. All under warranty. I will find out tomorrow what exactly it is. I will post when I find out.

 

[chapleaurocks]

So got my truck back today. They drove it all over and didn't act up. They scanned it and said no codes showed up at all. Maybe, it was a software glitch.

 

[beaker]

Call me a pessimist, but it's never just a software glitch. I say this having literally just walked in the door from hiking through some crazy deep snow to rescue my daughter; the "intermittent" stalling problem our snowmachine (that I had ignored) became a lot more permanent at a most inconvenient time and place.

Don't discount the throttle body, as this apparently is common enough in JLR engines to warrant a video.

This might be a red herring, since FoMoCo has their own part for the throttle body, but they still look strikingly similar. I hate to say it, but an EGR can also mimic the same thing.

Keep us updated if it comes back.

 

[chapleaurocks]

I will keep everyone updated. I agree with you. If it happens again I will take it to them and say figure it out.

 

[chapleaurocks]

So today my F150 did the same thing I've been botching about before. Code P0234. Can't get it in for a week. They asked me if the truck still drove the same. Do people lack common sense at dealers? If it drove the same qould I be calling. Anyway, I guess that software glitch was crap. Which I knew it was. So I will keep the group updated. Pisses off right now.

 

[navyR113]

I wonder if something like this would make a difference towards correcting the issue. If you could find/make something that would work in the same manner.

MAP-Maximizer Ford 7.3L & 6.0L Powerstroke Diesels

Fits: 1999-2007 Ford Powerstroke 7.3L/6.0LFits 1999-2003 Ford 7.3L Powerstroke Diesels. 2003-2007 Ford 6.0L Powerstroke Allows the MAP sensor to send a maximum allowed boost available signal to the PCM when overboosting. Eliminates the Service Engine Soon (SES) light from coming on when high

puredieselpower.com

 

[chapleaurocks]

This is what my scanner showed when I plugged it in. The bottom was the first issue a month ago. The top is what it showed last week.

 

[Dunrollin]

Strictly speaking this can only be from the turbo vanes being stuck on the full boost mode as I don't think our trucks have a waste gate. I am also guessing it could be faulty wiring, a bad sensor or even a defective PCM. A good Ford technician should be able to figure it out. This is from the Coffee Table book and explains the turbo operation.

Here is a screen shot that might also demonstrate it can be more than one sensor. I can't find a turbo overboost sensor, I am not sure if there is a specific sensor or if the PCM measures multiple sensors to determine an overboost condition. This screen shot mentions the ECT, MAF and MAP but not an overboost sensor. I just don't know.

Note on this that the overboost is detected by high exhaust pressure.

 

[chapleaurocks]

Strictly speaking this can only be from the turbo vanes being stuck on the full boost mode as I don't think our trucks have a waste gate. I am also guessing it could be faulty wiring, a bad sensor or even a defective PCM. A good Ford technician should be able to figure it out. This is from the Coffee Table book and explains the turbo operation.

View attachment 2548

Here is a screen shot that might also demonstrate it can be more than one sensor. I can't find a turbo overboost sensor, I am not sure if there is a specific sensor or if the PCM measures multiple sensors to determine an overboost condition. This screen shot mentions the ECT, MAF and MAP but not an overboost sensor. I just don't know.

View attachment 2549

Note on this that the overboost is detected by high exhaust pressure.

Thanks I am going to a different Ford dealer to see if they can fix the issue. Starting to piss me off this shouldn't happen.

 

[jmperlik]

@chapleaurocks - I believe that the root cause of @fharrison's P0234 Overboost ended up being a vacuum leak -- hopefully he can chime in if that's what he believes was the cause. See Post #64 in the START HERE: Any owners affected by FSA 18E02 (EGR By-pass valve replacement) thread and quoted below. If so, I'd have the new dealer specifically look for a vacuum leak, as it appears this one has your current Ford dealer stumped... I agree that this is something that Ford needs to address ASAP.

An update....dealer replaced the EGR but then found a vacuum leak. Have a feeling that was actually responsible for EGR efficiency and overboost problem since both of those are vacuum actuated. May have not been a problem with EGR at all. Will find out tomorrow.

Like I indicated earlier, @fharrison got his P0234 right in the middle of the original 18E02 EGR Bypass Valve recall = I probably should have split his P0234 issues off into a new thread at the time. Mea culpa!

@fharrison - did you ever get any additional F0234s after they fixed the vacuum leak?

 

[jmperlik]

@Dunrollin - interesting info you found:

I think you are probably right about there not being a specific overboost sensor per se, but rather I think the PCM is aggregating readings from those three (3) other sensors (ECT/MAP/MAF) to come up with a defacto "virtual" overboost via PCM programming. I only say this because they are giving you the actual math formula and timing under the "Typical Overboost Monitor Malfunction Thresholds" i.e.

IF (desired boost pressure - actual boot pressure) < ~15.0 kPA for > 7 seconds, THEN throw P0234 DTC

Breaking this down in layman's terms (not that I think I need to for this audience), the turbo is not reacting to the PCM for something more than 7 seconds = a pretty long time, which would be in line with something being stuck or something not working-as-design.

Coupling everything we know regarding P0234 to-date, I am going to assume the VGT part of the turbo is vacuum control, so I would be having the dealer check for the loose pin @fharrison said they found first and then verifying that the VGT is working-as-design (= there has to be a diagnostic test to verify this)

The last paragraph explains why they probably don't offer an engine brake option for our trucks, especially if this turbo does not use a waste gate, which I thought was a component of any turbo, but maybe the computer-controlled VGT eliminates the need for a waste gate?

Not an expert in any of this, but the engineer in me likes to try to understand how things work...

 

[chapleaurocks]

So is this a continuing problem that people have seen and documented, or is it my lucky day. Should I trade it in for a 6.7 ps.

 

[jmperlik]

@chapleaurocks - besides you, the only other report of a P0234 here on the forums by @fharrison, which I think was either a loose pin and/or vaccum leak. @fharrison is still active here on the forums, so if it was a continuing problem for him, I'm sure that he would be complaining about it now, as he's not something who I consider to be shy here.

Based on this I wouldn't say this is not a.) continuing nor b.) pervasive problem. I think you just need to find a dealer who can diagnose what is wrong. With a 2018 model, I think you are beyond any state Lemon Laws for recurring problems, but I do agree this is a serious recurring issue that needs to be resolved before something worse happens. The turbo is still covered by your 5yr/100K PowerStroke Engine Warranty, so I wouldn't be bailing and letting Ford off-the-hook quite yet.

 

[chapleaurocks]

So the dealership says everything points to the MAP sensor. Guess what, they are on a nation wide backorder. Scared to drive for fear of what might happen. Looking hard at a 6.7 ps.

 

[beaker]

Kind of sounds like you've already made up your mind. Just a couple points for consideration: A 6.7L will consume 30% more fuel; something to consider with the world's #2 oil producer invading a European country this week. It is also not immune to its own share of issues, including a TSB for snow in the air filter (from one of your other posts). Price out a DPF on a 6.7L versus a 3.0L, which is an item not included even on extended warranties since it is considered a wear item. I would argue that if you are looking for a drive it and forget it truck, you should be looking to a 5.0L F-150 or a Tundra.

If the MAP sensor is on backorder, there is at least one on eBay. I had one fail on one of my other vehicles; swapped it out in 10 minutes for $27. I was under warranty, but the hassle was not worth $27 to me.

As a final point, there is a note by @jmperlik a few posts up regarding the lack of a wastegate as a possible reason for the lack of an engine brake on this engine. I have 5 turbo vehicles including a 6.6L Duramax. None of them has a wastegate. In fact, the last wastegated turbo that I owned was a 1987 Audi Quattro. I think variable vane turbos have made wastegates redundant; in fact, it is the VVT that actually serves as the engine brake in vehicles coded to use them as such.

 

[chapleaurocks]

Kind of sounds like you've already made up your mind. Just a couple points for consideration: A 6.7L will consume 30% more fuel; something to consider with the world's #2 oil producer invading a European country this week. It is also not immune to its own share of issues, including a TSB for snow in the air filter (from one of your other posts). Price out a DPF on a 6.7L versus a 3.0L, which is an item not included even on extended warranties since it is considered a wear item. I would argue that if you are looking for a drive it and forget it truck, you should be looking to a 5.0L F-150 or a Tundra.

If the MAP sensor is on backorder, there is at least one on eBay. I had one fail on one of my other vehicles; swapped it out in 10 minutes for $27. I was under warranty, but the hassle was not worth $27 to me.

As a final point, there is a note by @jmperlik a few posts up regarding the lack of a wastegate as a possible reason for the lack of an engine brake on this engine. I have 5 turbo vehicles including a 6.6L Duramax. None of them has a wastegate. In fact, the last wastegated turbo that I owned was a 1987 Audi Quattro. I think variable vane turbos have made wastegates redundant; in fact, it is the VVT that actually serves as the engine brake in vehicles coded to use them as such.

Very useful information. Thank you.