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Discussion Starter · #1 ·
nearly finished my TDI conversion ( waiting on accelerator pedal and pot bracket) and vagcom has com back with 2 fault codes.

first is
00741 - brake pedal monitoring
27-10- implausible single intermittent

and

01262 - solenoid valve for boost pressure control valve n75
31-00 open or short to ground

any ideas? I thought I read somewhere that someone else had this problem but for the life of me I can't find it. tia steve:*
 

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Hello,

the first is a classic brake pedal switch error code. Have you connected up both brake circuits? One is for the ecu, the other for the lights -you need to reset the brake pedal switch and then reinstall quite possibly. There is also a connection to the ECU to check your brake lights.

The other error says the ECU is not reveiving a signal from the N75. Either it's not got power on the black/yellow wire or the ECU pin isn't connected. I don't have pin numbers and colours to hand as I'm on the phone. If it would help I'll post them up later
 

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Discussion Starter · #3 ·
Hello,

the first is a classic brake pedal switch error code. Have you connected up both brake circuits? One is for the ecu, the other for the lights -you need to reset the brake pedal switch and then reinstall quite possibly. There is also a connection to the ECU to check your brake lights.

The other error says the ECU is not reveiving a signal from the N75. Either it's not got power on the black/yellow wire or the ECU pin isn't connected. I don't have pin numbers and colours to hand as I'm on the phone. If it would help I'll post them up later
I have got penbryns ecu out list. brake lights come on when padal is pressed, I forgot to mention the glow plug light is flashing and goes out when the brake pedal is pressed.

when you say reset, do you mean clear the code's the reinstall the brake switch?

im using the turbo and manifold from my old abl engine,I have also blanked the egr valve would this give the fault code. I'm also using the old abl n75 does this need to be changed to the golf one? in which case do I need to change the whole lot over? ( manifold, turbo, n75, airbox etc from the golf) steve
 

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I think you're confusing the N18 and N75 valve. The egr has nothing to do with the n75. I've always used the GT15 turbo from the original engine - I believe it is possible to use the ABL one though... sorry not sure.

I would remove the switch by twisting it - pull out the actuator on the switch and reinstall.
 

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Discussion Starter · #5 ·
ah I see, am I right in saying the n18 is from the golf and the n75 is from the t4 abl? as the plug to the valve was different (golf plug was square) I cut and soldered the original t4 plug on. I may have wired it up wrong. do you know which wire goes to which pin?.

glow plug light is out but won't know if fault code is gone til the garage next door opens tomorrow. sorted this by changing the bottom brake switch to the one from the golf (originally the t4 switch and has a longer plunger on it)
 

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I have got penbryns ecu out list. brake lights come on when padal is pressed, I forgot to mention the glow plug light is flashing and goes out when the brake pedal is pressed.

when you say reset, do you mean clear the code's the reinstall the brake switch?

im using the turbo and manifold from my old abl engine,I have also blanked the egr valve would this give the fault code. I'm also using the old abl n75 does this need to be changed to the golf one? in which case do I need to change the whole lot over? ( manifold, turbo, n75, airbox etc from the golf) steve
The brake switch and brake light switch are separate. The (blue) brake switch is the one causing this fault and the flashing glowplug lamp.

As for the N75, you need to take this from the golf and pipe it up. to the turbo. IIRC you can use the N18 from the ABL, but to avoid any unnecessary issues, I'd use both from the Golf. I don't think the ABL has an N75 valve.
 

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What Law Anderson said. I'll look out pins later and post. You need to get the plumbing of pressure pipes (look the same as small vac pipes) from turbo to n75 to wastegate sctuator right too - it's not the same as the feedback circuit for the abl turbo...
 

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Ok so it's pin 47 for the ECU connection to the N75 (brown/blue wire usually) and pin 25 for the connection to the N18. You need both these sensors connected or the ECU will give you an error. They receive their feed on yellow/black wires directly from the 109 relay which you must also have. I suspect you just haven't connected up the N75 which you must do.

The N75 on a wastegate turbo tdi regulates pressure - such as the AHU/1Z/ACV. The N18 regulates vacuum to the EGR. The size of pipes used is the same. On a VNT set up such as Law Anderson has the N18 and N75 both regulate vacuum and are very similar.

You need to run a pipe from near the inlet manifold to the MAP sensor on the ECU - then you also need to regulate the wastegate pressure via the N75 according to something like this picture - you should have an N75 that looks like this from the donor car:

 

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I bypassed my n75 by connecting the turbo to wastegate as it was on my abl, just left the n75 plugged in to stop the fault code, had no problems and it pulls well, I did this on the advise of a mechanic and it works a treat, no more clicking n75
 

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Discussion Starter · #11 ·
I bypassed my n75 by connecting the turbo to wastegate as it was on my abl, just left the n75 plugged in to stop the fault code, had no problems and it pulls well, I did this on the advise of a mechanic and it works a treat, no more clicking n75

thanks dude I'll keep that in mind, I would rather plumb it in properly but if I can't find the info that I need then I'll go down that route.
 

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but a good idea to put a filter thingy on it - part number 702129965
or a cheap inline petrol fuel-filter (stops spiders climbing in LOL: )

Rich.
 

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thanks dude I'll keep that in mind, I would rather plumb it in properly but if I can't find the info that I need then I'll go down that route.
If your using the van turbo it is designed to run 100% boost as it did in your abl, so it works fine, less to go wrong and less vac pipes to worry about?
 

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Hi all I used the diagram posted and seems to have sorted all error codes. I was getting power loss on slight incline, pulls really well now
Still getting break error code any ideas
 
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