# TT not starting no power supply to ECU?



## jamie101 (Feb 5, 2017)

Hi there.
New member here. My name is jamie from rotherham south yorkshire. 
I have a 1999 V plate TT i baught cheap from a friend of mine as a non runner.
My problem is i seam to have no power supply to the ECU ir what i think!
I checked my fuel pump relay under the drivers dash pannel and other two relays under the bonnet on the right side (standing at the front of the car) of the bulk head all are working fine and contacts inside are very clean and if i click the fuel pump relay in it sends fuel direct to the fuel rail BUT on ignition not one of the relays are clicking to make up the circuit in order to start. Also no fuel is delivered to the fuel rail. Theres power to the relays and power to the injectors and power to the coil pack but still dosent start when i crank the car over. Also there is no engine management light lighting up on the dashboard when the ignition is turned on giving me the idea the ECU is not powering up? Just to note inhave checked all fuses on the drivers side fuse box and all are ok. Does anyone have any ideas what i could try next or have i missed anything that may need testing or checking? Next option is to have a look at the ECU and is their another relay in with the ECU inside the protective plastic box under the windscreen?
Thank you all in advance for any help.


----------



## Hoggy (May 8, 2002)

Hi, I would have mentioned the 2 relays under the bonnet marked 428 & 100, but you state they are both fine.
There is another member with a similar problem & I was surprised they don't have the relay labeled 100 & it is an early APX engined TT as is yours.
Relay 100 has been the problem in the past.
Do you have any faults codes ? 
Hoggy.


----------



## jamie101 (Feb 5, 2017)

Thank you for the reply.
I have delphi software on my laptop and it did come up with 'lateral throttle position sensor perminant fault' so i replaced that but i diddent think that would be related to my problem anyway but it did come up with no communication with the ECU which again makes me think theres no power to the ECU or a fault with the ECU its self maybe?
Thanks again. J


----------



## rusTTy_racer (Sep 7, 2015)

Are you saying you fitted a replacement throttle pedal, new or used? Do you have to adapt the new pedal?


----------



## jamie101 (Feb 5, 2017)

Hi there.
No not fitted a new throttle pedal just the lateral throttle position sensor the little black box above the clutch pedal - (held in place only by a big metal clip)
As far as it being adapted im not 100% sure how to make sure it is adapted? But like i say im sure that is not the reason its not starting up - but on the other hand i dont know thats why im asking you lads. You all have a better understanding than me.
Thank you.


----------



## spaceplace (Mar 10, 2013)

Immobiliser fault?


----------



## jamie101 (Feb 5, 2017)

Thanks again.
Dont think its immobiliser as the little light on the dash ( the car with the key) comes on with ignition then goes out when cranking to start. So i thaught if that was the immobiliser light that that would say the system is working as it should. Also when i plug it into my laptop it does have a function to scan the immobiliser and it says there are no faults there.
Bit of a head scratcher this one!
I can see it being somthing and nothing but finding the fault is proveing difficult.


----------



## Hoggy (May 8, 2002)

spaceplace said:


> Immobiliser fault?


Hi, Immobiliser fault will allow engine to start but will stop after a few seconds, immob key icon will also show.
Hoggy.


----------



## jamie101 (Feb 5, 2017)

Yes i thaught thats how the immobiliser worked on the TT but i wasent 100% sure. So like i say back to the drawing board! Still ECU related? Power supply to it or the ECU its self?
Anyone have anymore ideas or have had a similar problem?
I wont let it beat me!! Haha.


----------



## Hoggy (May 8, 2002)

Hi, Ignition switch fault perhaps. try putting 12volts directly to the relay marked 100.
Hoggy.


----------



## jamie101 (Feb 5, 2017)

Okie dokie. Ill give that a go in the morning. Its worth a try. That should that live up the ECU aswell maybe?


----------



## rusTTy_racer (Sep 7, 2015)

You clearly have a good grasp of the issues but just to clarify a couple of TT basics... I guess you know about the quattro second fuel pump when tank is 1/4 full can stop it running. If the water drain in the fuel filler cap is blocked then water might enter the tank. Does the rev counter rise to 200-300rpm when cranking?

How long ago did the car run!


----------



## spaceplace (Mar 10, 2013)

If you're able to pull fault codes then you must have coms with the ecu, I was under the impression that if the ecu was dead or there was no power to it then you couldn't connect to the ecu to pull any fault codes


----------



## spaceplace (Mar 10, 2013)

Isn't there also a crank sensor that can cause a non starting issue like the one you mention, I'd have thought this would bring a code up though.


----------



## jamie101 (Feb 5, 2017)

Thank youn all once again for the replys and advice.
I diddent know about the second fuel pump and the quarter tank of fuel issue with them i must admit!
So your saying if the fuel level drops below a quarter it COULD cause it not to start? Thats interesting the car does have approx a quarter tank of fuel or just under if i can remember rightly!
Not sure what the revs are at when cranking ill double check that tomorrow - what would this mean? Is 200 - 300 a normal rate for these cars when cranking over?
I dont think water in the fuel would be a problem as im not getting and fuel upto the rail unless i hold in the relay then it squirts out as it should. 
Its just seams to me asif the ECU has no power and just needs the power on ignition then everything will burst into life?
My laptop does the ISS - inteligent system scan which covers everything including immobiliser gearbox ABS systems etc aswell as the main ECU but when it gets to scan the ECU it just keeps saying system not responded which is the reason why i keep thinking is it just a power feed somewhere - relay fuse or a chaffed wire?
Its a bloody good one put it that way!!! Haha.
Really appriciate everyones input more heads are better than one!


----------



## jamie101 (Feb 5, 2017)

Sorry the last time the car was run was approx 3 weeks ago.


----------



## Hoggy (May 8, 2002)

Hi, If no RPM on tacho when cranking it points to faulty crank shaft speed sensor.
Hoggy.


----------



## jamie101 (Feb 5, 2017)

Ok. Im 95% sure i seen the needle moving on the clocks but ill check that in the morning also.
At least now you lads have put a few ideas forward for me i have a few more options to try. As i say i havent opened up the ECU box yet (under the screen on the drivers side) am i right in thinking there is a relay in there aswell? Someone told me theres a fuse in there aswell but dont know how true this is?


----------



## outdoor stevie (Nov 24, 2013)

The fuel tank has a hump in it where the propshaft for the four wheel drive goes so when the fuel in the half behind the driver drops low then the secondary pump behind the passenger seat pumps fuel over to the driver's side to keep the engine going. So if your fuel is low stick a couple of gallons in and if it fires up then I would suggest that your secondary pump is caput! Can you hear the main fuel pump pressurising the system when you turn the key but do not start it?

Stevie


----------



## Hoggy (May 8, 2002)

jamie101 said:


> am i right in thinking there is a relay in there aswell? Someone told me theres a fuse in there aswell but dont know how true this is?


Hi, As the ECU is well secured with tamperproof bolts etc & not easy to remove I wouldn't think so.
Hoggy.


----------



## jamie101 (Feb 5, 2017)

No i cant hear the pump primeing at all when the ignition is turned on or when the engine is cranking over.
Only wan i can make the pump run is to hold the contacts of the fuel pump relay down then fuel is delivered to fuel rail how it should.
BUT even if i do this and still crank the car to start - nothing.
I have power to injectors power to coil pack etc but just as if somthing is saying - do not start!


----------



## rusTTy_racer (Sep 7, 2015)

Yes, if second fuel 'pump' fails then fuel gets trapped in left hand side of tank due to the design. This can also happen if a previous owner has been in the tank! You could try a adding 5 or 10L of fuel to rule out.

Cranking with 200 revs shows crank sensor works.

Maybe worth checking plugs as they could be completely fouled after non starting.

Oh, bit slow lol! Relay only primes when ign on then waits for cranking/starts.

Is it a roadster or coupe?


----------



## jamie101 (Feb 5, 2017)

Quick update.
Just got back on the car noticed on cranking there is no movement on the rev counter whatsoever.
£17 for a new crank sensor so its worth a try but 2 more questions.....
Would this cause none of the relays to function?
And also location. Where is the crank sensor located?
You lads maybe able to tell me quicker than looking around and looking it up on computer.
Thanks again lads. J


----------



## Hoggy (May 8, 2002)

Hi, Bottom right of engine near gearbox/flywheel area.
Hoggy.


----------



## jamie101 (Feb 5, 2017)

Fitted the new crank sensor and still no change.
But i noticed the rev counter is still not moving when cranking the engine over. Still have no power to any of the three relays i mentioned?
Still thinking its a power feed issue?
Any secret fuses or relays i maybe missing?
Thanks again everyone.


----------



## spaceplace (Mar 10, 2013)

Maybe it is a faulty ecu, something must be telling it not to start, I know you say you have a good code reader but maybe it's worth trying vagcom on it? If you need a new ecu then you also need the dash clocks as they come in a pair and one won't work without the other. You should be able to get a second hand set for £200ish. But it could be something else. Saying that if you can't read the ecu then it would suggest it's broken. I always thought if the ecu was dead then you couldn't scan anything but could be wrong


----------



## Delta4 (Jun 19, 2015)

Ignition barrel playing up :?:


----------



## spaceplace (Mar 10, 2013)

This will sound stupid but have you tried disconnecting the battery for 10mins, it's a long shot but sometimes things can reset themselves. It free and worth a go, doubtful it will help but you never know


----------



## jamie101 (Feb 5, 2017)

Another update lads.
I just unpugged the ecu to check for power feeds when the ignition is turned on - turns out i only have one feed from the ignition switch and two other feeds one is the brake pedal position switch and the other is clutch position switch ?other than that all other feeds are dead? 
Im sure that on ignition there should be more than one feed into the ECU?
Beet cheeky but by any chance could anyone test theirs just to compare my readings. Im more concerned by the bigger connectors rather than the smaller little pins on both ecu plugs.
Real head scratcher this one!!!!


----------



## spaceplace (Mar 10, 2013)

Hopefully Wak might pop up


----------



## jamie101 (Feb 5, 2017)

Another update.
Laptop now saying - CAN BUS powertrain - code 01312
Bit lost on that one?
Any ideas?
Someone told me it may be the comfort control module as this supplys the power to the ECU??


----------



## Hoggy (May 8, 2002)

jamie101 said:


> Another update.
> Laptop now saying - CAN BUS powertrain - code 01312
> Bit lost on that one?
> Any ideas?
> Someone told me it may be the comfort control module as this supplys the power to the ECU??


Hi, This may help.
http://wiki.ross-tech.com/wiki/index.php/01312
Hoggy.


----------



## rusTTy_racer (Sep 7, 2015)

Worth checking the connectors that join the dash loom to the ECU one. All under a cover held down with a couple of bolts that is on the R/H side of the bulkhead (may need to remove wiper assembly to make it easier  ) above where your feet would be?


----------



## jamie101 (Feb 5, 2017)

Yes that does seem to cover it hoggy thank you for that. Ill check that wireing that nutty racer mentioned first but then if its not that ill give replaeing the CANBUS module.
I hear a cupple of you say that certain parts need 'adapting' when you replace certain items will i need VAGCOM to do this if i replace the CANBUS module or if i match yhe numbers is it plug and play?


----------



## auspicious_character (Sep 4, 2016)

I'm pretty sure I posted a vague way to get the car running already...

Once you untape the left ECU plug you will see the black/white wires, give them 12v from the battery and the car will live.

This simply bypasses all the relays, it does create a power drain and isn't a permanent solution but the car will work and be usable if you simply disconnect it nightly.


----------



## darren1984 (Jan 30, 2017)

Hey, how are you getting on with your car. I'm the other member with the same issue. I don't have relay 100 though, just the other one. I wonder if someone has had my loom stripped out and by passed this relay? Anyhow, I'm No further fwd and agree with you that ecu can't be getting power or its not earthed.

How did you check the fuel pump relay. Just take the cover off and click it yourself?

Many thanks

Darren


----------



## darren1984 (Jan 30, 2017)

auspicious_character said:


> I'm pretty sure I posted a vague way to get the car running already...
> 
> Once you untape the left ECU plug you will see the black/white wires, give them 12v from the battery and the car will live.
> 
> This simply bypasses all the relays, it does create a power drain and isn't a permanent solution but the car will work and be usable if you simply disconnect it nightly.


Can you give a little more detailed description of how to do this please. So is the wire black and white or is there a black wire and a white wire. Am I running positive from battery to this? And what about the negative, or will there be an earth being picked up? I've no real experience with car electronics. Almost an expert now with an audi tt. Thanks


----------



## auspicious_character (Sep 4, 2016)

Two black wires with a white strand running through them.
Once it is living I will educate with a relay bypass installation so it works as it should.


----------



## jamie101 (Feb 5, 2017)

Hi there darren1984.
Ive had to leave the TT a cupple of days as ive had aome work in i need to gt done on customers cars but im hoping to get back on the TT maybe wednesday this week.
Im no further on but my next job was to locate the CANBUS module and try to get a second hand one with numbers matching and replace that see if theres any change.
I also have a friend with VAGCOM who said he can plug the car in for me and make sure everything is coded in as it should be and to check nothing has lost its memory with this car being stood a while with a flat battery apperently the modules can loose memory and need a reboot to get them going again? 
As regaurds hard wireing the ECU im keeping that option as a last resort i appriciate the help and advice but im a little scared with anything like that due to a friend who did a similar thing and set his car on fire under the bonnet as he was driving down the road! 
Im not saying this will happen but im just a bit nervous about trying it at the moment.
Althogh a bit more information on how to do it would be good to try it to comfirm its an electrical problem we have with our cars.


----------



## jamie101 (Feb 5, 2017)

Sorry as regaurds checking the fuel pump relay all i did was take off the plastic cap then plug the relay back in and watch it on ignition - nothing happened so i just pushed the contacts together and i coupd hear the fuel pump run in the tank. I also took off the fuel feed pipe to the fuel rail put it in a bottle then did the same clicking the relay contacts together and there was fuel delivered into the bottle - no problem there.
I then thaughy inhad solved it by putting the pip back onto the fuel rail then by holding the relay closed and cranking the car i thaught it would start - but nothing! 
I then put it down to the ECU not telling the car to start.


----------



## auspicious_character (Sep 4, 2016)

A. It won't set on fire.....
B. Works for fault finding as you can pinpoint the problem and stop smelling like petrol


----------



## jamie101 (Feb 5, 2017)

I forgot to ask if anyone knows where the CANBUS module is located in the TT? Could anyone give me any idea please?


----------



## SPECSMAN (Oct 11, 2016)

This is getting complicated but.....

Listen to Auspicious_character; if he can make a TDI run in a Mk1, he knows his onions!

Specsman 8)


----------



## auspicious_character (Sep 4, 2016)

Making a tdi run in a Tt is easy.
So similar to the mk4 golf and they always break.


----------



## SPECSMAN (Oct 11, 2016)

auspicious_character said:


> Making a tdi run in a Tt is easy.
> So similar to the mk4 golf and they always break.


+1 to that!


----------



## jamie101 (Feb 5, 2017)

Haha. Ok point taken. Ill give it a go! Just that im a bugger for tracking down the route of the problem. Im like a dog with a bone somtimes BUT i have limited time and space so if it works it works. Ill give it a go as soon as i get a spare half hour. 
Which wires are needed on which ECU plug? Just the two black with white trace you say? Streight to live?
Thank you for your help and time. Some people these days wouldent even give time of day!! 
I appriviate it. Thanks.


----------



## darren1984 (Jan 30, 2017)

auspicious_character said:


> Two black wires with a white strand running through them.
> Once it is living I will educate with a relay bypass installation so it works as it should.


I'll be the test dummy for this troubleshoot test.

So 2 separate black wires with a white strip running through them. What exactly do I do here. I've got electrical cable ready long enough to reach. One will be to take a positive from the battery. Does it matter which one I then plug into?

I'll do it this afternoon if you can get back to be.

Thank you so much.

Darren


----------



## auspicious_character (Sep 4, 2016)

Just give both 12v, can be the same wire into both.
Then vroom.


----------



## darren1984 (Jan 30, 2017)

Ok got what I needed, started stripping back the tape to reveal the wires. My car came up trumps again. There is no black wire with white strip.


----------



## auspicious_character (Sep 4, 2016)

I'll find a pin out when I finish work.


----------



## auspicious_character (Sep 4, 2016)

I'll find a pin out when I finish work.


----------



## darren1984 (Jan 30, 2017)

Thanks. My car seems to be different. I don't have the relay I the engine bay marked 100 either just the 428.

Losing the plot

Thanks again


----------



## jamie101 (Feb 5, 2017)

Right another update!
I unwrapped the ECU wires on the multi plugs to find...........a broken wire........a main power feed wire to the ECU!!
YES FIXED I HEAR YOU SAY!!!!!.........dont be silly!!! haha.
I soldered the broken wire and tried the car it burst into life and started no problem....great i thaught....turned it off.....now it wont start again! This bloody car is making my head hurt!
I have power now to the ECU and power to all my relays theyre all working as they should all the dash lights are coming on and going out as they should my laptop says the immobiliser is working fine - no faults but still the car refuses to start again?
Although no i can get into the ECU and read the codes i have one that says throttle position sensor fault so this maybe my next port of call???


----------



## darren1984 (Jan 30, 2017)

How far from the multiplug was it broken and was it the larger one to the left of looking from the engine bay?

Thanks


----------



## jamie101 (Feb 5, 2017)

Yes mate the plug on the left as you are standing infront of the engine. It was broken about 2 - 3 inch down the loom. There is also another thin wire another inch further down i would advise you to check as mine was looking suspect so i repaired them all.
My 3 main broken ones were a thick red with green trace and a thin red with green trace both coming out of the loom and going into the ECU joining to a thin red with green trace coming out of the ECU. Hope it helps you out. J


----------



## darren1984 (Jan 30, 2017)

Mate, your a life saver. Exact same wire. I'll fix it tomorrow, it had some sort of corrosive green stuff on it.

If we never unwrapped this to find the black and white wire we would still be none the wiser. Thank you to the member who suggested this. In guessing his way would have worked in the end.

Thanks everyone. I'll update my post if and when the car runs.


----------



## jamie101 (Feb 5, 2017)

Chances of that eh?! 
Hope it fixes it ok for you mate as i say mines still being a little bugger at moment but ill sort it eventually.
Great that we both found the same problem like that hope it helps other TT owners in the future must be a comon fault due to the thin wire and water ingress wont take alot for it to rot away the copper wire.
Ill keep updateing the post untill mines up and running just so it helps other members if they have the same fault in future.
Keep us informed tomorrow mate if it gets yours going - fingers and toes crossed.!!!!


----------



## darren1984 (Jan 30, 2017)

Was exact same issue, same break. Must be a weakness in every loom surely.

Cleaned up, joined the 3 wires, soldered, heat shrunk, taped and car runs great. Better than ever.

Glad I found your post. Hope yours in running now too.

All the best

Darren


----------



## jamie101 (Feb 5, 2017)

Thats brilliant im well chuffed for you that its got yours back up and running!!
Mine on the other hand is still being a pain in the ass!
It did start as soon as i connected the wires back together but after i turned it off to try it again.....nothing
I now have EPC light staying on and the battery light? Still no engine management light though but all relays are clicking in ready to start the car so im thinking im nearly there now! 
Laptop says throttle angle position sensor this was changed by the previous owner to try to make it run after it broke down so i might put the original one back on and see what i get from that?
Any more ideas lads???


----------



## jamie101 (Feb 5, 2017)

Thats brilliant im well chuffed for you that its got yours back up and running!!
Mine on the other hand is still being a pain in the ass!
It did start as soon as i connected the wires back together but after i turned it off to try it again.....nothing
I now have EPC light staying on and the battery light? Still no engine management light though but all relays are clicking in ready to start the car so im thinking im nearly there now! 
Laptop says throttle angle position sensor this was changed by the previous owner to try to make it run after it broke down so i might put the original one back on and see what i get from that?
Any more ideas lads???


----------



## wassupcrew (Mar 16, 2021)

I know this is an older post, but hopefully so.eone can help. I have the same issues here. No power to pump unless I manually activate the relay. I have checked the ecu wiring and there are no broken wires there is only one black/white wire and that has 12v. Any ideas what it can be


----------

