Limp mode can't be found

[LimpModeVic]

I HAVE A VW 2004 T5 MULTIVAN, DIESEL, 2.5, 170PS

With the Limp Turbo problem. Between me and the VW Repair shops in the entire state, we have replaced the entire vacuum system, turbo (refurbished), intercooler, air filter and an oil change but the limp mode problem still exists.

Originally the limp mode problem was there but then the turbo started to go bad when it started squeezing and whistling. So I replaced that with what is supposed to be a refurbished original. After replacing the turbo, limp mode still exists when the engine is under high stress or pressure.

I took it to the shop for diagnosis. The computer reads with zero failures. That is what lead us to start looking into the sensor system. We systematically replaced all sensors dealing with the air system and the turbo. But replacing any sensor lead to no change in character.

I also replace the EGR unit, not just the valve but the whole housing.

With no change there that lead us to do a pressure check of the system but no problems were found. While looking a little closer at the intercooler, we noticed what looked like an oil leak around one of the vents so we removed the intercooler and put it under water for testing and found that it leaked air bubbles. This fault was not found in the original pressure testing. So today we have replaced the intercooler with a new one. BUT the engine still goes into limp mode after some time. Of course if the engine is turned off and then back on, it is reset and all is fine until it does it again.

The only two system that we have left are the electrical sys and the turbo itself. We are considering replacing the turbo with a brand new one, but this refurbished one should work just fine as it functions just fine up until limp mode. We simply have no other ideas of what to do.

I have been reading about this problem all over the internet and every single individual has a different answer to their problem. I have actually tried every one of those answers to no avail. VW has even called other partner shops in the area whom also have no answers.

The only other known fault in the entire vehicle is a bad oil sensor and a few parking sensors that need replacement.

Does anyone have any ideas that we have not tried?

 

[WelshGas]

N75 vacuum valve.
Accelerator potentiometer and wiring to EMU

Are there NO warning lights on dashboard?
No error codes at all?

Which Oil Sensor is problematic?

 

[LimpModeVic]

N75 vacuum valve.
Accelerator potentiometer and wiring to EMU

Are there NO warning lights on dashboard?
No error codes at all?

Which Oil Sensor is problematic?

Nope, not a single fault. I do not know which oil sensor is defect. I assumed it was the pan sensor since it peroidically says oil is low.

N75 was switched out. I / have not checked emu wiring though i figured that a wiring fault would register in computer?

 

[WelshGas]

If the oil sensor says Low then I believe this can trigger Limp Mode to protect the engine under load. So that is one thing to check.
As far as the wiring is concerned my reading of the various posts indicate a fault is not always registered.
Another thing I have found, the brake switch. Are your brake lights working correctly. Simple check and cheap repair.
Do let us know how you get on.

 

[LimpModeVic]

If the oil sensor says Low then I believe this can trigger Limp Mode to protect the engine under load. So that is one thing to check.
As far as the wiring is concerned my reading of the various posts indicate a fault is not always registered.
Another thing I have found, the brake switch. Are your brake lights working correctly. Simple check and cheap repair.
Do let us know how you get on.

In the morning, the oil is due to be changed. I will switch out the oil sensor then. After that it looks like i will have the use a volt meter to check all sensor wires. Any ideas where to start?

 

[WelshGas]

I would start at the EMU. Clean contacts etc likewise all the sensors and inputs from accelerator, brake etc. then the wiring and plugs. Visual check for any corrosion especially if the wires pass through any bulkheads etc. if clear then continuity checks.
I don't know about switching out the oil sensor. I would try and find out if it is the sensor, then replace, or wiring/ plugs.

 

[LimpModeVic]

I would start at the EMU. Clean contacts etc likewise all the sensors and inputs from accelerator, brake etc. then the wiring and plugs. Visual check for any corrosion especially if the wires pass through any bulkheads etc. if clear then continuity checks.
I don't know about switching out the oil sensor. I would try and find out if it is the sensor, then replace, or wiring/ plugs.

UNREAL!! Today I went and had the oil changed. While I was at it, I also changed the oil sensor. Normally the engine work was being done by Volkswagen but today the oil change was done by ATU. They did a print out from their diagnostic computer and had a totally diferent output than VW.

Failure Codes:
16683
17848
16627
19561
18062

Most of this has to do with the vacuum system related to the Turbo. I was so frustrated that I went directly to VW and told them. Of course they said there was no way that a 3rd party could diagnose my engine better than they could. They connected the Van to their VW computer and NO FAILURES.

It just so happens that every failure that ATU has listed, can cause a Limp Mode in the turbo or computer. Of course VW had no answer for that.

To make matters worse, as I told yall in the first entry, the entire vacuum system was switched out and tested, but the Limp Mode still existed. What they failed to do was get a computer reading or any type of measurements at all from each and ever sensor or ventil switch. I am pretty sure I am not paying for that one.

It would seem to me that with all of these failures, perhaps there is a central node somewhere that is related to these? I recon it can be that even of these parts is failing but unlikely?

 

[LimpModeVic]

Check this out, so since it appears that after 3 weeks, VW has no measurements from any parts that they have replaced, I started to do electronic checks today, myself. I tested the MAF sensor to find all is ok. I tested the N75 and found 11.3v with engine running. That is ok range.

BUT on the otehr sensor in the picture above, for supply voltage it is sporadic from 2 - 11.7v with engine running. Does that seem right? Reason I am asking is because one of the spec criteria for the MAF is that the supply voltage is a steady supply. TO me a sporadic voltage supply is a problem. it certainly would be for my Arduino projects.

 

[LimpModeVic]

Check this out, so since it appears that after 3 weeks, VW has no measurements from any parts that they have replaced, I started to do electronic checks today, myself. I tested the MAF sensor to find all is ok. I tested the N75 and found 11.3v with engine running. That is ok range.

BUT on the otehr sensor in the picture above, for supply voltage it is sporadic from 2 - 11.7v with engine running. Does that seem right? Reason I am asking is because one of the spec criteria for the MAF is that the supply voltage is a steady supply. TO me a sporadic voltage supply is a problem. it certainly would be for my Arduino projects.

N75 is on the bottom. I believe the next one up is the N18, but the top most one with the spradic readings, I do not know what that is.

 

[snowy55]

I'm sorry I can't help you with your problem but have tried asking on the T5 section on this site?
http://www.vwt4forum.co.uk/