HELP please.... SDi to TDI conversion

funbagjuggler · Jan 15, 2012

Hi all
I have just converted an S reg SDi Caddy van to TDi (1Z) from a MK3 Golf
I stripped the MK3 loom to just leave all the wires that go to/from ECU
I then taped this up so is kind of stand alone loom
I have fitted this in the van, it plugged straight in to the loom on the engine
I have connected to all the sensors under the bonnet (N75, MAF, EGR etc)
In the van all I had to connect was the throttle pedal, immo box and G1 + G2 connectors
Did this, van started first flick of the key, HAPPY DAYS

Fitted exhaust on etc so could take it from the workshop to home to fit the interior
but this is where the problem started........

It seems that just as it starts to come on boost, it suddenly holds back....
Wont pull any more.......

I got it home and fitted a boost gauge to see if it was loosing boost, but it doesnt
Will hold 1 bar, but wont rev
If it were a petrol its like its got no ignition advance

I have plugged my vagcom in and pump timing etc all seem to be good
MAF readings seem fine
The only screen thats puzzling me, and I dont know why I'm getting these reading is in
ENGINE
MEASURING BLOCKS
BASIC SETTINGS
Group 07 Temperatures

It reads
Fuel temp -30.1*C
Intake Air Temp -40.5*C
Coolant temp -18.0*C

I DONT THINK SO!!!!!

Temp gauge in instruments is reading 90*C
If I disconnect the temp sensor on the engine, gauge drops but VagCom reading stays the same.........

I'm guessing I have put a live or earth where it shouldn't be but wiring is not my strong point.......

Can anybody shed a bit of light on where I should be looking please
I have wiring diagrams but not current flow so cant check what voltage in what wire etc.
Although MAF readings are right, in fault codes it says MAF short to plus (00553 code-nothing on Ross Tech) but as I say, starts and runs, just doesnt pull......

Any help would be much appreciated
Many thanks, Gavin

m1keh · Jan 15, 2012

Definitely a problem with some wiring somewher. When I get on my other computer I will check the ecu wiring diagram for you to see any common wires between those temp senders.

Jon Olds · Jan 15, 2012

Bit off thread (sorry);
Interesting conversion, and problem.
I have a 1z on the workshop floor and a full car harness. I started the disconnections well, labelling everything under the bonnet. But a mate helped me strip the car, so removing the through bulkhead stuff was a bit 'tear it apart'. Its mostly linked back up now, but I still have unconnected plugs/sockets
How did you approach the stripping of the harness to just maintain what you needed to run the engine? Help appreciated if forthcoming, as I havent done anything like this before.

funbagjuggler · Jan 15, 2012

Jon Olds said: ↑

Bit off thread (sorry);
Interesting conversion, and problem.
I have a 1z on the workshop floor and a full car harness. I started the disconnections well, labelling everything under the bonnet. But a mate helped me strip the car, so removing the through bulkhead stuff was a bit 'tear it apart'. Its mostly linked back up now, but I still have unconnected plugs/sockets
How did you approach the stripping of the harness to just maintain what you needed to run the engine? Help appreciated if forthcoming, as I havent done anything like this before.
Click to expand...

Held the 2 plugs that go into the ecu and stripped all the black looming tape off.
The loom goes for about a ft as a fat loom then splits in to 2
1 part goes towards large connector for engine
other heads in towards the fusebox,but also heads to OSF
with connectors for MAF, N75 and EGR valves
The end that goes to the fuse box has :-
G1 & G2 connectors on
plug for throttle pedal
plugs for brake and clutch pedal
grey n white wire for immo box
and a couple of other randoms that hang about,
1 being for cruise control (flat black connector with 4 wires)

Think thats it from memeory
Basically cuttin out light, wiper and ABS wiring
I left the vans original loom for lights and wipers

Does any of that make sense?

Jon Olds · Jan 15, 2012

Thanks, that sounds logical, and gives me a good starter for 10

rubjonny · Jan 16, 2012

see my sig for a wiring diagram, from your diagnostics id say you are missing a sensor earth. see pages 3,4 and 7, look at '220 earth connection (sender earth)'. this runs back to ecu pin 33 so check the various sensor earth pins for continuity back to the ecu.

funbagjuggler · Jan 17, 2012

rubjonny said: ↑

see my sig for a wiring diagram, from your diagnostics id say you are missing a sensor earth. see pages 3,4 and 7, look at '220 earth connection (sender earth)'. this runs back to ecu pin 33 so check the various sensor earth pins for continuity back to the ecu.
Click to expand...

Thanks RJ, I will check that
I clicked on ur link, but was told i needed an account
I set up an account
Now when i click ur link, it goes to Google and says
NOTHING MATCHES YOUR SEARCH!!!!

I HATE COMPUTERS!!!!!

What am i doing wrong now?

Brookster · Jan 17, 2012

TDI Conversion (everything you need to know)

http://www.vwt4forum.co.uk/showthread.php?t=95358

Loads of info for 1Z installs on the T4 Forum

penbryn said: ↑

Common 1.9TDI Conversion Issues

This is a short companion to all of the guides for converting the VW T4 to 1.9TDI power. I have tried to compile a list of common problem descriptions and solutions that seem to crop-up time and again in the hope that it will be useful to others. This list is by no-means exhaustive and I welcome suggestions for inclusion (within reason).

1. Engine Multiplug Connector

This connector can be the source of many problems for a number of different reasons. Many of the problems can manifest themselves as faults flagged by the ECU such coolant temp. sensor, crank sensor, etc. Equally, it can also cause gauges or warning lights on the instrument cluster to behave strangely (flashing oil/handbrake warning indicators at ignition off) or not work at all.

Another point related to this connector is the fact that the metal bracket (shown above) is a ground point for the instrument temp. gauges via the 10mm nut shown above. If you remove this bracket from the engine block/head and it is floating (i.e. not connected to ground via the block/cyl. head) the instrument cluster will behave strangely with flashing/pulsatingwarning indicators with the ignition off. The fuel/temp gauges may also read incorrectly/erratically with ignition on.

Things to watch out for:

Most people are unaware of the fact that the two parts of the connector should first be engaged and then turned clockwise until a distinct 'click' is felt/heard. If you do not feel this 'click' then the connector is not fully 'home' or 'seated' which means that some connections may not be 'made'

This connector can also suffer from corroded pins so a visual inspection is also worth doing along with a quick spray with contact cleaner.

2. Turbo Wastegate

If your van is a 1.9TD prior to carrying-out the TDI conversion, chances are you will have played with the wastegate actuator in order to increase the boost and hence squeeze a few more HP from the engine. On a TD engine, the actuator rod length controls the level of boost i.e. the shorter the actuator rod is the more boost it takes to overcome the mechanical resistance of the spring open the wastegate. This is fine for the TD engine, but can cause problems for the TDI as the wastegate is opened and hence boost regulated by the ECU.

On the TDI motor the level of boost is set by the ECU, so once the MAP (Manifold Absolute Pressure) sensor detects that the boost is about to reach the preset threshold it opens the N75 solenoid (actually N75 is modulated - switched on and off quickly) but we'll ignore that for the sake of explanation). This means that there is now a direct link between the actuator and the compressor housing of the turbo so that it can open the wastegate and reduce boost.

Obviously the step response of the 'actual boost' will never follow the commanded boost exactly (blue in the diagram). This due to the latency (delay) of the mechanical components etc. However, the ECU s/w has been designed to essentially ignore the spike or overshoot in boost under normal conditions (plus there is also some hysteresis built-in to the control loop to prevent oscillation). However if this is 'overshoot' exceeds the boost limit for more than a predefined time window then the ECU will enter limp mode.

The problem with the wastegate on the TDI motor is that the more tension that is on the actuator rod the harder it is for the compressed air from the turbo to open it (meanwhile remember that the boost is still climbing - as illustrated by the yellow trace in the diagram above). If the boost gets to the maximum allowable threshold before the wastegate is opened fully you get limp mode or an oscillation ('hunting') of the control loop . By reducing the tension on the rod, boost is regulated more quickly as the peak boost required to open the wastegate is lower. A badly adjusted rod can also cause a sort of pulsating of the boost as the control loop oscillates.

How to set-up the wastegate actuator for the TDI motor:

a) Remove the circlip from the wastegate (A).
b) Open the locknut on the actuator rod (B)
c) Remove the actuator from the wastegate (C)
d) Loosen off the rod until the 'hole' fits easily over the (closed) wastegate lever (C)
e) Remove the rod from wastegate again and turn it 8 turns clockwise.
f) Refit the rod to the wastegate, tighten the locknut, and refit the circlip.

3. Instrument Cluster

As most of you are aware (and contrary to rumours spread by those who think that it must be magic ), the VW T4 instrument cluster can be retained if you convert to 1.9TDI. There are a few minor changes to be made. In order to make these changes however, a basic understanding of how DOP works is essential. It should be noted that this change is not always required, but I will cover it here as it can potentially cause problems with 1996-> instrument clusters.

So, what is DOP and why does it cause problems?

VAG vehicles have been using the DOP (dynamic oil pressure) system since the 1980's, this means that two oil pressure switches and engine RPM are used to determine oil pressure rather than the system of a single switch. The rationale behind the DOP system is that low oil pressure problems are typical of high-mileage VAG engines with worn bearings and oil that is hot (and thin). The combination of thin oil and worn main bearings means that the oil pressure is marginal at lower RPM where the oil pump is not spinning as fast as it does when driving. Basically the instrument cluster monitors the low pressure sensor when the engine is below 2000 rpm and the high pressure sensor above 2000 RPM.

The problem for the TDI conversion is that the later (96->) instrument clusters cannot read the engine RPM from the ECU (so DOP will not work and the oil pressure indicator will just flash) as it is a different frequency to that of the alternator W teminal. The later clusters have better signal conditioning (presumably to comply with EMC regs) and so the TDI ECU signal is ignored by the cluster. This will result in a flashing oil warning indicator at all engine speeds.

How to solve the DOP problem.

Basically all you need to do is remove the ECU generated signal from pin 12 of connector G1 on the fusebox and connect the 'w' signal. To do this cut the black/green wire coming from the ECU tape it up and then connect the 'w' terminal of the alternator to pin 12 G1 (bottom right-hand pin in the pic below).

4. 109 Relay

The infamous 109 relay seems to cause more than its fair share of problems. This is due to the fact that VAG have consistently specified a component whose rating lies right on the limits for the current carrying capacity for the contacts of the relay.

Generally one of the following is what tends to happen:

a) The contacts arc and corrode causing intermittent starting and/or strange unrelated faults to be logged by the ECU.

b) The coil goes o/c in the relay - no ECU comms, no start, dead.

c) The metal pins soldered to the relay contacts 'dry-out' caused by the fact the the contacts are always working on the limit of their current carrying capacity. Again this will cause difficult or non-starting/stalling/No ECU comms etc.

d) The contacts arc and stick (basically weld themselves together). This means that the contacts are permanently closed even at ignition off and also that all of the sensor/pump supplies are still powered-up. The giveaway to when this problem happens is that the modulating piston in the fuel pump can be heard buzzing away under the bonnet. Apart from the buzzing everything seems to work, but it will flatten your battery sharpish and can damage sensors as well as the pump if allowed to continue.

Generally speaking the aftermarket replacement relays are usually of better quality than the original VAG part as the current handling capacity of the relay tends to be higher. VAG are aware of the problem but their 'improved' replacement part seems no better than the original and is also prone to failure.

If you suspect 109 failure, remove the relay and short the contacts. If you engine starts and runs as normal, replace 109.

4. Brake Switches

The brake and clutch switches are something that are often overlooked when doing the TDI conversion and sometimes people ignore them by either disconnecting them or hardwiring them so that the effects of any faults are masked (but not eliminated). This actually has safety implications however and you should not do this .

The brake switches have three functions in terms of the electronic control of the TDI engine:

1. Most importantly, the brake switches function (in tandem) in the manner of safety interlock, such that if there is a fault with the throttle sensor where the throttle is for instance stuck at WOT, then the brake input or switch over-rides any throttle input, thus allowing the driver to bring the vehicle under control. if you eliminate the switch or indeed the brake input signal then this will not happen and it therefore has the potential to be fatal - BOSCH/VAG installed this feature to ensure that the system was fail-safe, by removing it you risk making it unsafe.

2. When the ECU senses a braking input, it decreases the amount of injected fuel thereby reducing engine shudder and helping to save fuel.

3. The brake signal is used by the ECU to disable cruise (when active).

The brake monitoring system uses two different signals to determine when the brakes have been pressed: 1) An independent ECU switch 2) a brake (lights) signal input which is fed from the switched side of the vehicle brake light switch. Problems occur when:

1. The ECU 'sees' a signal on the switch but nothing on the brake light circuit or vice versa. e.g blown brake lamp bulbs
2. One signal is 'seen' before or after another. - i.e when the switches are not setup to trigger at the same time.

5. ECU 'Memory' Fault

I have have had a number of enquiries from people regarding this fault but until recently I had never experienced it myself. Basically what happens is that the ECU reports a fault such as:

and try as you might you can't clear it from the fault memory.

There are actually a number of things that can cause this, and quite often people replace the ECU in order to eliminate it thinking that it must be a hardware problem. However it can actually be caused by:

1. A split in the hose from the MAP nipple on the outside of the ECU housing to the pressure transducer (inside the ECU - see diagram below) for sensing boost. When this happens the boost from the turbo basically pressurises the ECU housing and the (other) baro sensor inside the ECU (for determining geographic altitude) goes haywire. The upshot is that the ECU reports this rather erroneous memory fault!

2 A faulty 109 relay has also known to cause this fault.

3. Poor/high resistance in the battery ground for the ECU is also another common one.

To be continued
Click to expand...

Brookster · Jan 17, 2012

penbryn said: ↑

IMPORTANT NOTE:

My apologies to all about this note at the beginning of the article but I have lost count of the number of times I have had people PM me looking for fault-finding advice but without any idea of what is causing the fault on their conversion because they do not have a means to interrogate the ECU/immo.

Please get either a copy of VAGCOM/VCDS or a reliable fault reader before starting the tdi conversion.

It is an absolutely essential piece of equipment due to the electronic control on these engines. Without some way to interrogate the ECU or immo you are peeing in the wind as you will never know what the faults are or what is causing the particular undesirable behaviour you are experiencing - it's a bit like trying to play chess in the dark. Please do not PM me about your non-running TDI conv. if you do not have a reliable fault-reader with the ability to retrieve DTC's [/soapbox]

1.9TDI Conversion Wiring

I have finally decided to tackle the write-up of the information that I have collected for this part of the 1.9 TDI conversion in the hope that it may be useful to others. I have opted divide this into 2 parts. In this first one I will cover the wiring and connectors you need to keep for the fusebox, brake switch, immobiliser, etc.

The basis for this write-up is an engine bay wiring harness from a 1997 VW Golf 1.9TDI 1Z/AHU engine code with the Bosch 68 pin ECU. However, much of the info (including wiring colour codes) is applicable to other donor vehicles and engine codes. Although, I should mention that some (but not all ) SEAT vehicles use a different colour coding scheme, the wiring will be the same and can be checked using a multimeter between the ECU connector and the signal wire in question with the info below.

So what connectors and parts of the wiring harness (loom) do I need to keep and what can I throw away?

Well, I have decided to try to keep things as simple as possible such that you can avoid chopping wires and generally 'butchering' the loom. To start with I stripped the insulating tape off the harness between the 'branches' so that I could sort the individual leads. You will need a large flat surface for this (a cleared garage floor is what I used) else things start to get out of hand and you'll end-up feeling very frustrated indeed with your pile of spaghetti

The easiest thing to do is to identify the connectors outlined below and remove all others and strip the wiring to them out of the harness/loom as they will not be required. A basic rule-of-thumb is: if it doesn't lead to the ECU or one of the associated sensor connectors or engine, you don't need it!

For the Golf engine bay harness, having spread it out on the floor along its length, you will see that the ECU connector, engine circular multiplug and associated sensor connectors are at one end. At the other end, is the Golf lighting/horn/etc. circular multiplug and harness on its own. All of the fusebox connectors are about 1/4 of the way along the harness from the circular lighting multiplug.

Pic.1 - Lighting Wiring Harness multiplug

This multiplug and harness is connected electrically to the rest of the engine bay harness only by means of a series of ground wires (plain brown) which can be cut but we'll come to that later. The easiest thing to do at this point before cutting any wires is to start slicing the harness tape along its length (or simply unravel it if you like - I found it easier to slice open however) around the 'A1' and 'A2' multiplugs (they will only fit in locations A1 and A2 on the fusebox) and the red 4 pin connector (shown in the picture below).

Pic.2 - A1, A2 and 4 pin red connector on the lighting harness

Once you have opened the tape and removed it, tease these three plugs loose (otherwise read: 'untangle while cursing VW to hell') from the rest of the wiring and connectors. Having done this you will see that all that connects this part of the harness to the rest is two/three brown ground wires and a single brown/red which connects to pin 5 of connector G1 - these can be cut, safe in the knowledge that the remnants will be removed later - see Pic.7 of fusebox and connectors below noting pin 5.

Once this has been removed you will be left with a harness that has fusebox connectors at one end, and engine connectors at the other. So, working your way along (towards the ECU connector) slice the tape open until you reach the end of the heavy positive lead (it has a heavy eyelet and battery connector attached to it) shown below - this is the main supply from the battery to the fusebox but your van will have this already, so it's not needed. This can now be lifted clear of the main harness.

Pic.3 - Battery +VE to fusebox lead

The next step is to remove the battery ground lead -ve which is mainly connected to a series of brown wires which are not associated with the engine control. Starting at the fusebox-end locate the heavy brown wire with the spade connector on it as shown below.

Pic.4 - Fusebox to battery -VE lead

Tease this out of the harness all the way to the end until you are met by a piece of clear heatshrink. The brown lead enters this and emerges the other side as a black lead with a lug which is normally connected to battery -VE NOTE DO NOT REMOVE THE OTHER BLACK LEAD (also with a lug) THAT GOES TO THE ECU CONNECTOR you will need this! You will see that it is connected to 6 other smaller brown wires in the heatshrink as shown below (except that I have cut these down in the pic but you can see the stubs). Some of these will have previously been connected to the lighting circuit that you cut earlier (remember?).

Pic.5 - Battery negative leads joined in harness

Lift as much of this whole mess out of the harness as you can. You will notice that some of the small brown wires are connected to the next bit of harness that we are going to remove so snip them away.

The last bit of unused harness to be removed is shown in the pic below. It basically involves the steps described previously. I have no idea what this stuff originally was used for as I did not remove the harness from my donor vehicle and I just havent had the time to check the circuit diagrams out to find out where they should've been. Suffice to say they are not needed and can be cut out. Getting back to the fusebox connectors locate multiplug 'C' and tease this out of the loom. You will find that it is connected to the mess illustrated below which can all be lifted out of the loom including the 2 white connectors with the green wires which were originally connected to the wiper circuit in the Golf.

Pic.6 - Remaining unused bits of the harness which can be discarded

After all the ripping and tearing, for the fuse box and cabin wiring, you will need to keep the following

Pic.7 - Multiplugs F, G1, and G2 which plug into the fusebox itself

Pic.8 - The glowplug supply and fuseholder

Pic.9 - The throttle position sensor multiplug

Pic.10 - ...and these.

Following the numbering scheme in the diagram above:
1) Brake Pedal Switch
Blue 2 pin connector
Pin1 = brown/white -> analogue ground -> pin 33 ECU
Pin2 = white/yellow -> pin 20 ECU
This is connected to the ECU and must be triggered at the same time as the main vehicle brake light signal (see 4 below ). It is used by the ECU to reduce the injected fuel quantity under braking as well as deactivate cruise control.

2) Vehicle Speed Signal
Blue single pin connector = blue/white tracer -> pin 43 ECU
Used to assess the vehicle speed, and is fed through from the instrument cluster. This signal is used to maintain vehicle speed when cruise control is activated.

3) Clutch Pedal Switch
Black Connector
Pin1 = brown/white -> analogue ground -> pin 33 ECU
Pin2 = white/red -> pin17 ECU
Used by the ECU, to tell when the clutch is engaged, injected fuel quantity is then reduced briefly to alleviate
engine shudder when changing gear. Also used as a signal to deactivate cruise control if currently active.

4) Brake Pedal Input
Green single pin connector = black/red -> pin44 ECU
This signal is used in conjunction with the brake pedal switch above to reduce the injected fuel quantity and hence as a safety interlock to over-ride a faulty throttle position sensor. It is connected to the brake light switch (switched side) via junction box TV11 on the golf fusebox. No actual provision is made for this on the T4 harness but it can be connected directly to the switched side of the T4 brake circuit (either: (1) pin4 connector W (2) pin4 of connector K or (3) pin3 of connector 'E' on the fusebox whichever is most convenient).

5) K-line comms.
Brown single pin connector = grey/white -> pin61 ECU
If your car has an immobiliser it will be connected to this line and then via a loop-through to the OBD 2 socket. If you do not have an immobiliser (pre 1995 vehicles) this is connected directly to the OBD 2 socket.

6) Cruise Control Connector
Black 4 pin connector and green single pin connector
Pin 1 black -> igniton switched +12V supply,
Pin 2 blue/grey -> pin34 ECU,
Pin 3 red -> pin35 ECU,
Pin 4 black/white -> pin66 ECU,
if you retrofit cruise control, connect the cruise control harness to this connector and enable the ECU.

7) Fuel Consumption signal
Black 3 pin connector
Pin 1 purple/white -> pin9 ECU
Pin 2 black/white -> fusebox or lighting somewhere
Pin 3 green/black -> fusebox or lighting loom somewhere
This is connected to pin 9 of the ECU and is a PWM signal which is generated by the ECU based on the amount of fuel injected at any given instance. It is used in conjunction with the VSS (vehicle speed signal) by the high-end instrument clusters to calculate Miles-Per-Gallon. This wire can be omitted if you do not have an MFA (multifunction display) cluster, (or do not intend to install one in the future). When separating the lighting harness from the engine one you will need to cut the wires that lead to pins 2 and 3 of this connector. Note: this signal/connector may be missing in some donor vehicles, so don't be too-surprised if you can't find it!

** One important note here is that if your engine/wiring harness was sourced from an older vehicle (pre '95), there will also be an extra connector and sensor to look out for called a barometric pressure sensor, which lives in the cabin also. The sensor and connector are shown below.

Pic.11 Barometric sensor and wiring (photo and wire colour codes courtesy of golfgtioz)

Black 3 pin connector
Pin 1 green / purple -> pin41 ECU
Pin 2 brown / white -> ground -> pin33 ECU
Pin 3 green / red -> pin40 ECU
This sensor is used by the ECU to adjust fueling and EGR levels depending on the geographical altitude of the vehicle - i.e air is less dense at higher altitudes so fuel is adjusted accordingly. This sensor is built into later >'95 ECUs and should not concern you if your donor vehicle was manufactured in 1995 or afterwards.

So now that I have the necessary wiring sorted do I need to change anything else?

Yes, on the fusebox you will need to make the following changes:

1) Change the relay in position 12
Firstly you will need to change the relay in position 12 of the T4 fusebox from '104' to relay '103' that came with the Golf.

2) Add relay to position 3
You will also need to add the '109' relay (ECU +12V / "terminal 30" supply) to the empty position 3 of the T4 fusebox. See diagram below.

Pic.12 - Relay plate

This is the most important part of wiring for the 1.9 TDi. I will try to cover the remainder (minor modifications etc) when I finally get around to gathering all of the details together and try to find the relevant photos. Hope this is of help.
Click to expand...

rubjonny · Jan 17, 2012

funbagjuggler said: ↑

Thanks RJ, I will check that
I clicked on ur link, but was told i needed an account
I set up an account
Now when i click ur link, it goes to Google and says
NOTHING MATCHES YOUR SEARCH!!!!

I HATE COMPUTERS!!!!!

What am i doing wrong now?
Click to expand...

must have been a problem with the site, works fine for me even when im logged out of google!

does this work:
https://docs.google.com/leaf?id=0B_...WRhZS00MzBkLTk2MTEtNGIyZDFmMDg0NWM2&cindex=72

Jon Olds · Jan 17, 2012

great stuff

funbagjuggler · Jan 17, 2012

rubjonny said: ↑

must have been a problem with the site, works fine for me even when im logged out of google!

does this work:
https://docs.google.com/leaf?id=0B_...WRhZS00MzBkLTk2MTEtNGIyZDFmMDg0NWM2&cindex=72
Click to expand...

Ha ha ha!!
Was tryin to view in mobile not desktop (option at bottom of screen!)
Doh!!

@Brookster - thanks for that,great info there
1 question though, I have no F fuse box connector in the loom I fitted
I cut it out of the 1Z loom, but left the original van loom in
Lookin on the A2resource site, the wires into the F connector are starter,
alternator exciter wire and others that don't go to the ecu.

This shouldn't be a problem should it?
As I said, it started and drove home from yard ok.
No warning lights on or anything, just won't pull......
I'm gonna have a look at it again tomorrow, been busy last couple of nights

I'll report on my findings

Thanks for your help Guys

Gavin

Jon Olds · Jan 17, 2012

Following with interest

m1keh · Jan 17, 2012

Check that connector 33 on your ecu plug is making continuity with the earth sides of your temp sensors. Probably the easiest one to get to is the intake air. Disconnect the ecu plug and intake air temp sensor plug and measure for continuity between pin 33 and the brown white wire on the intake air temp sensor plug.

I think you might find their is a break in that earth circuit somewhere.

rubjonny · Jan 18, 2012

theres nothing on F that you need specifically, but its easier to keep it if say doing a swap into a mk2 with the tdi box as it has the starter, alternator and alternator plugs in the right place for the TDI cable shift box and alternator wiring. but you can use the old stuff no worries

funbagjuggler · Jan 21, 2012

Well.....
.... the saga continues......

Its definately an earth problem
I did the continuity test between terminal 33 and sensor earths
All good

Tested Vagcom again, same readings

Disconnected the AIT sensor, no difference to readings
Disconnected temp sensor, no difference to readings (on vagcom)

So, frustrated at this point, started bridging wires with a fused piece of wire
and
when I bridged 2 wires on the temp sensor plug the revs dropped to normal
revs (It had been revving a little high) and seemed smoother
Checked vagcom readings and temps all spot on
Happy Days
The 2 wires bridged were ecu earth (brown/blue) and the sensor earth
(brown/white) thats bolted to block........

So this would tell me the ecu isnt earthing properly
It must be be earthing though or it wouldnt run at all....

Temps before earthing were all minus as before
After earthing :-
Fuel temp 32.9
Air intake temp 24.3
Coolant temp 74.7

There were 5 fault codes in engine module before bridging the earth
They were :-

00553 - Mass air flow sensor (G70)
28-00 - Short to plus

00539 - Fuel Temperature Sensor (G81)
30-00 - Open or Short to Plus

00777 - Accelerator Position Sensor (G79)
27-00 - Implausable Signal

00741 - Brake Pedal Monitoring
27-10 - Implausable Signal - Intermittent

00527 - Intake Manifold Temperature Sensor (G72)
30-00 - Open or Short to Plus

They went after bridging though......

I checked the main ECU to battery earth and thats good
I have an earth from gearbox/block bolt to battery
Am i missing a head to battery/body earth....????

Any more help?
Thanks for the pointers so far

Gavin

rubjonny · Jan 23, 2012

the brown/white wire to block is probably the dash earth, simply tap into the ecu pin 33/sensor earth somewhere and earth it to the block

funbagjuggler · Jan 23, 2012

rubjonny said: ↑

the brown/white wire to block is probably the dash earth, simply tap into the ecu pin 33/sensor earth somewhere and earth it to the block
Click to expand...

Done that
All looks good now
wired in an avry mod (?) but not tried it or road tested the van yet

Going to get a seat in tonight and try it up the road

I'll report back as to how it goes

Thanks All

Gavin

stifla · Sep 4, 2013

funbagjuggler said: ↑

Held the 2 plugs that go into the ecu and stripped all the black looming tape off.
The loom goes for about a ft as a fat loom then splits in to 2
1 part goes towards large connector for engine
other heads in towards the fusebox,but also heads to OSF
with connectors for MAF, N75 and EGR valves
The end that goes to the fuse box has :-
G1 & G2 connectors on
plug for throttle pedal
plugs for brake and clutch pedal
grey n white wire for immo box
and a couple of other randoms that hang about,
1 being for cruise control (flat black connector with 4 wires)

Think thats it from memeory
Basically cuttin out light, wiper and ABS wiring
I left the vans original loom for lights and wipers

Does any of that make sense?
Click to expand...

Hi mate !!! I know this thread is yonks old but need some help with my s reg caddy tdi conversion same as yours. I have an AHU tdi sitting in a golf on my drive ready to donor into my caddy. I can pull the engine no sweat but wiring I'm not the best at lol ! You said your ecu had 2 plugs but mine only has one big one so I'm thinking me chopping into loom to isolate off lights etc isn't poss ? Also did you caddy run an over the top gearbox cable that's different to the golf gearbox top arm system (which did you end jo using ? Also which way did you go with immo because the golf key is as smooth as a babies bum now and my caddy key is sweet. I've pulled out immo box and barrel coil but the grey white wire is a proper pain in the butt so I've left that in there for now but do I need it or will the caddy have same wiring so I can just change out the immo box ????

Really sorry to pick your brains mate but just need a few pointers so I don't do some stuff I don't need to lol

Cheers bud

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HELP please.... SDi to TDI conversion

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