P0234 Turbo/overboost

6362 Views 36 Replies 7 Participants Last post by PeteK, 10 mo ago

chapleaurocks

Discussion Starter · Jan 8, 2022

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.

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Dunrollin

· #2 · Jan 8, 2022

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

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chapleaurocks

Discussion Starter · #3 · Jan 8, 2022

I will.

jmperlik

· #4 · Jan 8, 2022

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

Vehicle: 2018 Lariat 3.0L V6 PSD

Current mileage?
Actual ODB code/number thrown? P0234?
Status of 18E02 EGR By-Pass valve recall?
Status of 20E04 EGR By-Pass valve recall?
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?
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...

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chapleaurocks

Discussion Starter · #5 · Jan 8, 2022

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

Vehicle: 2018 Lariat 3.0L V6 PSD

Current mileage?

Actual ODB code/number thrown? P0234?

Status of 18E02 EGR By-Pass valve recall?

Status of 20E04 EGR By-Pass valve recall?

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?

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.

Reactions: 2

chapleaurocks

Discussion Starter · #6 · Jan 13, 2022

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.

Reactions: 1

beaker

· #7 · Jan 13, 2022

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.

Reactions: 2

chapleaurocks

Discussion Starter · #8 · Jan 13, 2022

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

Discussion Starter · #9 · Feb 2, 2022

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

· #10 · Feb 2, 2022

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.

puredieselpower.com

MAP-Maximizer Ford 7.3L & 6.0L Powerstroke Diesels

Fits: 1999-2007 Ford Powerstroke 7.3L/6.0L Fits 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

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chapleaurocks

Discussion Starter · #11 · Feb 6, 2022

2

White Light Product Mobile phone Mobile device

Light Communication Device Gadget Font Output device

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.

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Dunrollin

· #12 · Feb 6, 2022

2

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.

Font Household hardware Auto part Engineering Machine

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.

Font Material property Parallel Number Screenshot

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

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chapleaurocks

Discussion Starter · #13 · Feb 6, 2022

Dunrollin said:
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

· #14 · Feb 6, 2022

@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.

fharrison said:
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

· #15 · Feb 6, 2022

@Dunrollin - interesting info you found:

Font Material property Parallel Number Screenshot

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.

Code:

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...

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chapleaurocks

Discussion Starter · #16 · Feb 6, 2022

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

· #17 · Feb 6, 2022

@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.

Reactions: 2

chapleaurocks

Discussion Starter · #18 · Feb 22, 2022

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

· #19 · Feb 23, 2022

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.

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chapleaurocks

Discussion Starter · #20 · Feb 23, 2022

beaker said:
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.

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