Turbocharger/Supercharger Boost Sensor "A" Circuit High

Jane And Rog

Jane And Rog

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Adria Twin 640 SGX
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We’re in the Anti Atlas mountains in Morocco and the engine warning light came on a couple of days ago and the van went into limp mode. We managed to find a guy with and ODB and the error is Error is P0238 Turbocharger/Supercharger Boost Sensor "A" Circuit High which isn’t great but is fixable here. However we cleared the error and high stationary revs didn’t cause it again. We’ll go for a test drive today.

Any thoughts on this strategy? We’re at about 1000m. Van is a 2.3 2018 Ducato and it had a quantum remap last year.
 
Last edited:
Jane And Rog said:
We’re in the Anti Atlas mountains in Morocco and the engine warning light came on a couple of days ago and the van went into limp mode. We managed to find a guy with and ODB and the error is Error is P0238 Turbocharger/Supercharger Boost Sensor "A" Circuit High which isn’t great but is fixable here. However we cleared the error and high stationary revs didn’t cause it again. We’ll go for a test drive today.

Any thoughts on this strategy? We’re at about 1000m. Van is a 2.3 2018 Ducato and it had a quantum remap last year.
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We had the same error code that put us into limp mode while on a fast motorway in France last year.
With not much of a hard shoulder to speak of and fast traffic and trucks blasting past, it was not a pleasant experience. Tried starting our van a few times but it remained in limp mode and not reving.
We always carry a Bluetooth code reader for the OBD port with us and the "Torque" app on my phone, so we quickly knew what the error code was, and looked it and its causes up on the internet.
I checked all turbo pipework, wiring and wiring connectors which all appeared fine, so I cleared the error code, and all appeared back to normal and has been since with it not being repeated.
I think what caused ours to throw up the error was that we were just cresting a long hill in a lower gear and when I changed up a gear and floored the throttle, I think that the turbo spun up and went over its boost pressure limit causing the error.

I had our van remapped with a Quantum remap, but that was 5 years ago.
 
Just joining your stories together and question if the accelerant’s in the air from the paint work, made your engine rev higher than it thought it should be, at that time. Causing the turbo to spin. Thus throwing a wobbly.

if you spray brake cleaner, easy start, that sort of thing near an engine intake the revs will rise.

Just a thought.
 
If you can locate the sensor you could always take it out and clean it. Worst case you could order one to be delivered to a local adress and fitted out there. They are not expensive.
 
Is it possible that your remap didn't compensate for the effects of less dense air at altitude?

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Thanks all, will point Rog back at this thread. We set off Towards Tiznit thus morning but 5km the error light cane back on. Revs weren’t limited in the same way so we carried on but power was definitely not there when climbing & burning through the diesel so we’ve returned to Tafaroute rather than risk getting stuck.
 
Check your air filter. I’ve know people to put rag (and other items) on slam panels of vehicles whilst working on them, and with Ducato’s it is the air intake, and people don’t know this.
And this can happen
51D866DE-0BAB-41FA-BDC6-35E2C144100D.jpeg
 
The default Fiat map is pretty conservative. Maybe a combination of a remap that pushes things closer to the limits, maybe fuel that isn't up to the same spec, and the altitude was enough to put it outside expected values and it threw a wobbly?
 
Guigsy said:
The default Fiat map is pretty conservative. Maybe a combination of a remap that pushes things closer to the limits, maybe fuel that isn't up to the same spec, and the altitude was enough to put it outside expected values and it threw a wobbly?
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Not motorhome related, however, when I visited Morroco the second time on my motorbike I had fueling issues. I put it down to altitude, the fuel & the way the bike was set up to meet the european emmision standards. It never cut out, but always felt like it was going to.
 
When we go across in the defenders we take super diesel in cans, as the local stuff isn’t always great, and you need the power in the dunes. We always get more smoke on their fuel.

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Thanks everyone. As Jane said we tried to leave the valley but the warning light/limp mode came back on as soon as we hit the first serious hill.

We found a mechanic - or more accurately he found us - and we drove 94km over the pass in second gear to his workshop. I could tell the van had more power below ~700m but it’s still not driving well. He has an ODB and the error is the same. We’re hoping it’s a dirty sensor so he’ll clean it tomorrow. Maybe get an oil change and a new filter at the same time. It’s a bit annoying because we had the van serviced ~6 months ago. I guess they don’t take the turbo to bits and polish the sensors.
 
I’m not sure the sensor will be on the turbo. It may be taking its reading from the MAP sensor.
 
How much black smoke are you getting, and is it whilst accelerating hard. The rest of the time ok? Any whooshing sound at same time from engine area?

Just a thought but the intercooler goes across the front of the van at the bottom, and the pipe from it curves around in the bumper section just in front of the wheel. Could it be possible when you hit the tree stump, that you punctured the pipe, pulled the pipe off, or damaged the end on intercooler.

A damaged intercooler, or it‘s pipework will cause black smoke on acceleration, loss of boost (power) and the van won’t understand why the engine isn’t receiving the boost that the turbo is pushing out. Also the fuel range wouldn’t be accurate as the two sensors MAF and MAP are seeing different volumes so it can’t calculate.
 
Landy Andy said:
How much black smoke are you getting, and is it whilst accelerating hard. The rest of the time ok? Any whooshing sound at same time from engine area?

Just a thought but the intercooler goes across the front of the van at the bottom, and the pipe from it curves around in the bumper section just in front of the wheel. Could it be possible when you hit the tree stump, that you punctured the pipe, pulled the pipe off, or damaged the end on intercooler.

A damaged intercooler, or it‘s pipework will cause black smoke on acceleration, loss of boost (power) and the van won’t understand why the engine isn’t receiving the boost that the turbo is pushing out. Also the fuel range wouldn’t be accurate as the two sensors MAF and MAP are seeing different volumes so it can’t calculate.
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I agree with Andy here, it definitely sounds like you have a potential boost (air) leak, meaning overfueling (black smoke), loss of grunt (less dense air entering the engine) and confusion for the sensors based on the boost you’re making and the boost your getting at the inlet manifold being different.

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Jane And Rog said:
Landy Andy spot on although not a cloth. We had mice over winter and it looks like they ate some of the bonnet lagging then stashed their leavings in the air filter. 🐭
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Easy fix then.. 👍🏻

Strange how even in a more analogue society one encounters in Morocco, that they don’t resort to checking simple things first, rather they plug in diagnostics like everyone else. 🤣
 
Jane And Rog said:
Landy Andy spot on although not a cloth. We had mice over winter and it looks like they ate some of the bonnet lagging then stashed their leavings in the air filter. 🐭
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WOW. I’m gobsmacked. Hope all is well now and the rest of your fab trip is incident free 👍🏼

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There is also a lot of soot in the engine so it’s being cleaned up. Not massively happy about the service I had six months ago - I guess we can’t blame the mice on them though :)
 
When you get it going ,it may be best to put premium deisel in rather than the lowest bruce deisel.
Best of luck
 
Jane And Rog - it would be good to complete this topic and post about the cause of your problem and fix in this thread (as well as the travel one) so if anyone is searching in the future, they get to see the complete route cause was indeed boost loss, not just the mice! 👍🏻
 
Very true. So it looks like there are two problems causing this, maybe three. I don’t really know if we can define any as the root cause. Still, the problems were:
  • very sooty engine, including the boost pressure sensor due to:
  • partially blocked air filter caused by mice eating insulation and
  • pressure loss from a cracked (intake) host due to the prang.
I’d like to say “if you see this problem, check for cracked/loose hoses and change your air filter” but I think that wouldn’t have cleared the fault in my case because of the soot which I think was caused by 1000s of miles through the uk and France with the mice ridden filter. It’s certainly a good start though.

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Once you get on the merrygoaround of overfuelling (soot generation) on the twin egr models this can lead to real agravation. To be aware read the link. It also has instructions how to remove the MAP sensor. The P0401 can accompany P0236 P0238.
www.fiatforum.com

Ducato twin EGR Engine with P0401 Code (2016 to 2019)

This does not refer to earlier single EGR systems or to later AdBlu SCR engines. Note this is a guide and not definative. It is up to you to make decissions. It is the result of my investigations of data from many contributors and discussion with...
www.fiatforum.com www.fiatforum.com
 

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